OgnlContext 源码

// Copyright (c) 1998-2004, Drew Davidson and Luke Blanshard
package ognl;

import ognl.enhance.LocalReference;

import java.util.*;

/**
 * This class defines the execution context for an OGNL expression
 * 
 * @author Luke Blanshard (blanshlu@netscape.net)
 * @author Drew Davidson (drew@ognl.org)
 */
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;
    
    static {
        String s;
        
        RESERVED_KEYS.put(CONTEXT_CONTEXT_KEY, null);
        RESERVED_KEYS.put(ROOT_CONTEXT_KEY, null);
        RESERVED_KEYS.put(THIS_CONTEXT_KEY, null);
        RESERVED_KEYS.put(TRACE_EVALUATIONS_CONTEXT_KEY, null);
        RESERVED_KEYS.put(LAST_EVALUATION_CONTEXT_KEY, null);
        RESERVED_KEYS.put(KEEP_LAST_EVALUATION_CONTEXT_KEY, null);
        RESERVED_KEYS.put(CLASS_RESOLVER_CONTEXT_KEY, null);
        RESERVED_KEYS.put(TYPE_CONVERTER_CONTEXT_KEY, null);
        RESERVED_KEYS.put(MEMBER_ACCESS_CONTEXT_KEY, null);

        try {
            if ((s = System.getProperty(PROPERTY_KEY_PREFIX + ".traceEvaluations")) != null) {
                DEFAULT_TRACE_EVALUATIONS = Boolean.valueOf(s.trim()).booleanValue();
            }
            if ((s = System.getProperty(PROPERTY_KEY_PREFIX + ".keepLastEvaluation")) != null) {
                DEFAULT_KEEP_LAST_EVALUATION = Boolean.valueOf(s.trim()).booleanValue();
            }
        } catch (SecurityException ex) {
            // restricted access environment, just keep defaults
        }
    }

    private List _typeStack = new ArrayList();
    private List _accessorStack = new ArrayList();

    private int _localReferenceCounter = 0;
    private Map _localReferenceMap = null;

    /**
     * Constructs a new OgnlContext with the default class resolver, type converter and member
     * access.
     */
    public OgnlContext()
    {
    }

    /**
     * Constructs a new OgnlContext with the given class resolver, type converter and member access.
     * If any of these parameters is null the default will be used.
     */
    public OgnlContext(ClassResolver classResolver, TypeConverter typeConverter, MemberAccess memberAccess)
    {
        this();
        if (classResolver != null) {
            this._classResolver = classResolver;
        }
        if (typeConverter != null) {
            this._typeConverter = typeConverter;
        }
        if (memberAccess != null) {
            this._memberAccess = memberAccess;
        }
    }

    public OgnlContext(Map values)
    {
        super();
        this._values = values;
    }

    public OgnlContext(ClassResolver classResolver, TypeConverter typeConverter, MemberAccess memberAccess, Map values)
    {
        this(classResolver, typeConverter, memberAccess);
        this._values = values;
    }

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

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

    public Map getValues()
    {
        return _values;
    }

    public void setClassResolver(ClassResolver value)
    {
        if (value == null) { throw new IllegalArgumentException("cannot set ClassResolver to null"); }
        _classResolver = value;
    }

    public ClassResolver getClassResolver()
    {
        return _classResolver;
    }

    public void setTypeConverter(TypeConverter value)
    {
        if (value == null) { throw new IllegalArgumentException("cannot set TypeConverter to null"); }
        _typeConverter = value;
    }

    public TypeConverter getTypeConverter()
    {
        return _typeConverter;
    }

    public void setMemberAccess(MemberAccess value)
    {
        if (value == null) { throw new IllegalArgumentException("cannot set MemberAccess to null"); }
        _memberAccess = value;
    }

    public MemberAccess getMemberAccess()
    {
        return _memberAccess;
    }

    public void setRoot(Object value)
    {
        _root = value;
        _accessorStack.clear();
        _typeStack.clear();
        _currentObject = value;

        if (_currentObject != null)
        {
            setCurrentType(_currentObject.getClass());
        }
    }

    public Object getRoot()
    {
        return _root;
    }

    public boolean getTraceEvaluations()
    {
        return _traceEvaluations;
    }

    public void setTraceEvaluations(boolean value)
    {
        _traceEvaluations = value;
    }

    public Evaluation getLastEvaluation()
    {
        return _lastEvaluation;
    }

    public void setLastEvaluation(Evaluation value)
    {
        _lastEvaluation = value;
    }

    /**
     * This method can be called when the last evaluation has been used and can be returned for
     * reuse in the free pool maintained by the runtime. This is not a necessary step, but is useful
     * for keeping memory usage down. This will recycle the last evaluation and then set the last
     * evaluation to null.
     */
    public void recycleLastEvaluation()
    {
        OgnlRuntime.getEvaluationPool().recycleAll(_lastEvaluation);
        _lastEvaluation = null;
    }

    /**
     * Returns true if the last evaluation that was done on this context is retained and available
     * through <code>getLastEvaluation()</code>. The default is true.
     */
    public boolean getKeepLastEvaluation()
    {
        return _keepLastEvaluation;
    }

    /**
     * Sets whether the last evaluation that was done on this context is retained and available
     * through <code>getLastEvaluation()</code>. The default is true.
     */
    public void setKeepLastEvaluation(boolean value)
    {
        _keepLastEvaluation = value;
    }

    public void setCurrentObject(Object value)
    {
        _currentObject = value;
    }
    
    public Object getCurrentObject()
    {
        return _currentObject;
    }
    
    public void setCurrentAccessor(Class type)
    {
        _accessorStack.add(type);        
    }
    
    public Class getCurrentAccessor()
    {
        if (_accessorStack.isEmpty())
            return null;
        
        return (Class) _accessorStack.get(_accessorStack.size() - 1);
    }
    
    public Class getPreviousAccessor()
    {
        if (_accessorStack.isEmpty())
            return null;

        if (_accessorStack.size() > 1)
            return (Class) _accessorStack.get(_accessorStack.size() - 2);
        else
            return null;
    }

    public Class getFirstAccessor()
    {
        if (_accessorStack.isEmpty())
            return null;

        return (Class)_accessorStack.get(0);
    }

    /**
     * Gets the current class type being evaluated on the stack, as set by {@link #setCurrentType(Class)}.
     * 
     * @return The current object type, may be null.
     */
    public Class getCurrentType()
    {
        if (_typeStack.isEmpty())
            return null;

       return (Class) _typeStack.get(_typeStack.size() - 1); 
    }
    
    public void setCurrentType(Class type)
    {
        _typeStack.add(type);
    }
    
    /**
     * Represents the last known object type on the evaluation stack, will be the value of
     * the last known {@link #getCurrentType()}.
     * 
     * @return The previous type of object on the stack, may be null.
     */
    public Class getPreviousType()
    {
        if (_typeStack.isEmpty())
            return null;

        if (_typeStack.size() > 1)
            return (Class)_typeStack.get(_typeStack.size() - 2);
        else
            return null;
    }
    
    public void setPreviousType(Class type)
    {
        if (_typeStack.isEmpty() || _typeStack.size() < 2)
            return;

        _typeStack.set(_typeStack.size() - 2, type);
    }

    public Class getFirstType()
    {
        if (_typeStack.isEmpty())
            return null;

        return (Class)_typeStack.get(0);
    }

    public void setCurrentNode(Node value)
    {
        _currentNode = value;
    }

    public Node getCurrentNode()
    {
        return _currentNode;
    }

    /**
     * Gets the current Evaluation from the top of the stack. This is the Evaluation that is in
     * process of evaluating.
     */
    public Evaluation getCurrentEvaluation()
    {
        return _currentEvaluation;
    }

    public void setCurrentEvaluation(Evaluation value)
    {
        _currentEvaluation = value;
    }

    /**
     * Gets the root of the evaluation stack. This Evaluation contains the node representing the
     * root expression and the source is the root source object.
     */
    public Evaluation getRootEvaluation()
    {
        return _rootEvaluation;
    }

    public void setRootEvaluation(Evaluation value)
    {
        _rootEvaluation = value;
    }

    /**
     * Returns the Evaluation at the relative index given. This should be zero or a negative number
     * as a relative reference back up the evaluation stack. Therefore getEvaluation(0) returns the
     * current Evaluation.
     */
    public Evaluation getEvaluation(int relativeIndex)
    {
        Evaluation result = null;

        if (relativeIndex <= 0) {
            result = _currentEvaluation;
            while((++relativeIndex < 0) && (result != null)) {
                result = result.getParent();
            }
        }
        return result;
    }

    /**
     * Pushes a new Evaluation onto the stack. This is done before a node evaluates. When evaluation
     * is complete it should be popped from the stack via <code>popEvaluation()</code>.
     */
    public void pushEvaluation(Evaluation value)
    {
        if (_currentEvaluation != null) {
            _currentEvaluation.addChild(value);
        } else {
            setRootEvaluation(value);
        }
        setCurrentEvaluation(value);
    }

    /**
     * Pops the current Evaluation off of the top of the stack. This is done after a node has
     * completed its evaluation.
     */
    public Evaluation popEvaluation()
    {
        Evaluation result;

        result = _currentEvaluation;
        setCurrentEvaluation(result.getParent());
        if (_currentEvaluation == null) {
            setLastEvaluation(getKeepLastEvaluation() ? result : null);
            setRootEvaluation(null);
            setCurrentNode(null);
        }
        return result;
    }

    public int incrementLocalReferenceCounter()
    {
        return ++_localReferenceCounter;
    }

    public void addLocalReference(String key, LocalReference reference)
    {
        if (_localReferenceMap == null)
        {
            _localReferenceMap = new LinkedHashMap();
        }

        _localReferenceMap.put(key, reference);
    }

    public Map getLocalReferences()
    {
        return _localReferenceMap;
    }

    /* ================= Map interface ================= */
    public int size()
    {
        return _values.size();
    }

    public boolean isEmpty()
    {
        return _values.isEmpty();
    }

    public boolean containsKey(Object key)
    {
        return _values.containsKey(key);
    }

    public boolean containsValue(Object value)
    {
        return _values.containsValue(value);
    }

    public Object get(Object key)
    {
        Object result;

        if (RESERVED_KEYS.containsKey(key)) {
            if (key.equals(OgnlContext.THIS_CONTEXT_KEY)) {
                result = getCurrentObject();
            } else {
                if (key.equals(OgnlContext.ROOT_CONTEXT_KEY)) {
                    result = getRoot();
                } else {
                    if (key.equals(OgnlContext.CONTEXT_CONTEXT_KEY)) {
                        result = this;
                    } else {
                        if (key.equals(OgnlContext.TRACE_EVALUATIONS_CONTEXT_KEY)) {
                            result = getTraceEvaluations() ? Boolean.TRUE : Boolean.FALSE;
                        } else {
                            if (key.equals(OgnlContext.LAST_EVALUATION_CONTEXT_KEY)) {
                                result = getLastEvaluation();
                            } else {
                                if (key.equals(OgnlContext.KEEP_LAST_EVALUATION_CONTEXT_KEY)) {
                                    result = getKeepLastEvaluation() ? Boolean.TRUE : Boolean.FALSE;
                                } else {
                                    if (key.equals(OgnlContext.CLASS_RESOLVER_CONTEXT_KEY)) {
                                        result = getClassResolver();
                                    } else {
                                        if (key.equals(OgnlContext.TYPE_CONVERTER_CONTEXT_KEY)) {
                                            result = getTypeConverter();
                                        } else {
                                            if (key.equals(OgnlContext.MEMBER_ACCESS_CONTEXT_KEY)) {
                                                result = getMemberAccess();
                                            } else {
                                                throw new IllegalArgumentException("unknown reserved key '" + key + "'");
                                            }
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            }
        } else {
            result = _values.get(key);
        }
        return result;
    }

    public Object put(Object key, Object value)
    {
        Object result;
        
        if (RESERVED_KEYS.containsKey(key)) {
            if (key.equals(OgnlContext.THIS_CONTEXT_KEY)) {
                result = getCurrentObject();
                setCurrentObject(value);
            } else {
                if (key.equals(OgnlContext.ROOT_CONTEXT_KEY)) {
                    result = getRoot();
                    setRoot(value);
                } else {
                    if (key.equals(OgnlContext.CONTEXT_CONTEXT_KEY)) {
                        throw new IllegalArgumentException("can't change " + OgnlContext.CONTEXT_CONTEXT_KEY
                                + " in context");
                    } else {
                        if (key.equals(OgnlContext.TRACE_EVALUATIONS_CONTEXT_KEY)) {
                            result = getTraceEvaluations() ? Boolean.TRUE : Boolean.FALSE;
                            setTraceEvaluations(OgnlOps.booleanValue(value));
                        } else {
                            if (key.equals(OgnlContext.LAST_EVALUATION_CONTEXT_KEY)) {
                                result = getLastEvaluation();
                                _lastEvaluation = (Evaluation) value;
                            } else {
                                if (key.equals(OgnlContext.KEEP_LAST_EVALUATION_CONTEXT_KEY)) {
                                    result = getKeepLastEvaluation() ? Boolean.TRUE : Boolean.FALSE;
                                    setKeepLastEvaluation(OgnlOps.booleanValue(value));
                                } else {
                                    if (key.equals(OgnlContext.CLASS_RESOLVER_CONTEXT_KEY)) {
                                        result = getClassResolver();
                                        setClassResolver((ClassResolver) value);
                                    } else {
                                        if (key.equals(OgnlContext.TYPE_CONVERTER_CONTEXT_KEY)) {
                                            result = getTypeConverter();
                                            setTypeConverter((TypeConverter) value);
                                        } else {
                                            if (key.equals(OgnlContext.MEMBER_ACCESS_CONTEXT_KEY)) {
                                                result = getMemberAccess();
                                                setMemberAccess((MemberAccess) value);
                                            } else {
                                                throw new IllegalArgumentException("unknown reserved key '" + key + "'");
                                            }
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            }
        } else {
            result = _values.put(key, value);
        }
        
        return result;
    }

    public Object remove(Object key)
    {
        Object result;

        if (RESERVED_KEYS.containsKey(key)) {
            if (key.equals(OgnlContext.THIS_CONTEXT_KEY)) {
                result = getCurrentObject();
                setCurrentObject(null);
            } else {
                if (key.equals(OgnlContext.ROOT_CONTEXT_KEY)) {
                    result = getRoot();
                    setRoot(null);
                } else {
                    if (key.equals(OgnlContext.CONTEXT_CONTEXT_KEY)) {
                        throw new IllegalArgumentException("can't remove " + OgnlContext.CONTEXT_CONTEXT_KEY
                                + " from context");
                    } else {
                        if (key.equals(OgnlContext.TRACE_EVALUATIONS_CONTEXT_KEY)) {
                            throw new IllegalArgumentException("can't remove "
                                    + OgnlContext.TRACE_EVALUATIONS_CONTEXT_KEY + " from context");
                        } else {
                            if (key.equals(OgnlContext.LAST_EVALUATION_CONTEXT_KEY)) {
                                result = _lastEvaluation;
                                setLastEvaluation(null);
                            } else {
                                if (key.equals(OgnlContext.KEEP_LAST_EVALUATION_CONTEXT_KEY)) {
                                    throw new IllegalArgumentException("can't remove "
                                            + OgnlContext.KEEP_LAST_EVALUATION_CONTEXT_KEY + " from context");
                                } else {
                                    if (key.equals(OgnlContext.CLASS_RESOLVER_CONTEXT_KEY)) {
                                        result = getClassResolver();
                                        setClassResolver(null);
                                    } else {
                                        if (key.equals(OgnlContext.TYPE_CONVERTER_CONTEXT_KEY)) {
                                            result = getTypeConverter();
                                            setTypeConverter(null);
                                        } else {
                                            if (key.equals(OgnlContext.MEMBER_ACCESS_CONTEXT_KEY)) {
                                                result = getMemberAccess();
                                                setMemberAccess(null);
                                            } else {
                                                throw new IllegalArgumentException("unknown reserved key '" + key + "'");
                                            }
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            }
        } else {
            result = _values.remove(key);
        }
        return result;
    }

    public void putAll(Map t)
    {
        for(Iterator it = t.keySet().iterator(); it.hasNext();) {
            Object k = it.next();

            put(k, t.get(k));
        }
    }

    public void clear()
    {
        _values.clear();
        _typeStack.clear();
        _accessorStack.clear();

        _localReferenceCounter = 0;
        if (_localReferenceMap != null)
        {
            _localReferenceMap.clear();
        }

        setRoot(null);
        setCurrentObject(null);
        setRootEvaluation(null);
        setCurrentEvaluation(null);
        setLastEvaluation(null);
        setCurrentNode(null);
        setClassResolver(DEFAULT_CLASS_RESOLVER);
        setTypeConverter(DEFAULT_TYPE_CONVERTER);
        setMemberAccess(DEFAULT_MEMBER_ACCESS);
    }

    public Set keySet()
    {
        /* Should root, currentObject, classResolver, typeConverter & memberAccess be included here? */
        return _values.keySet();
    }

    public Collection values()
    {
        /* Should root, currentObject, classResolver, typeConverter & memberAccess be included here? */
        return _values.values();
    }

    public Set entrySet()
    {
        /* Should root, currentObject, classResolver, typeConverter & memberAccess be included here? */
        return _values.entrySet();
    }

    public boolean equals(Object o)
    {
        return _values.equals(o);
    }

    public int hashCode()
    {
        return _values.hashCode();
    }
}