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General data-binding functionality for Jackson: works on core streaming API

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package com.fasterxml.jackson.databind;

import java.lang.reflect.Modifier;

import com.fasterxml.jackson.core.type.ResolvedType;

/**
 * Base class for type token classes used both to contain information
 * and as keys for deserializers.
 *

 * Instances can (only) be constructed by
 * com.fasterxml.jackson.databind.TypeFactory
 * (included in "jackson-databind")
 */
public abstract class JavaType
    extends ResolvedType
    implements java.io.Serializable
{
    // for 2.1.0:
    private static final long serialVersionUID = -5321897246493723158L;

    /**
     * This is the nominal type-erased Class that would be close to the
     * type represented (but not exactly type, due to type erasure: type
     * instance may have more information on this).
     * May be an interface or abstract class, so instantiation
     * may not be possible.
     */
    protected final Class _class;

    protected final int _hashCode;

    /**
     * Optional handler (codec) that can be attached to indicate 
     * what to use for handling (serializing, deserializing) values of
     * this specific type.
     *

     * Note: untyped (i.e. caller has to cast) because it is used for
     * different kinds of handlers, with unrelated types.
     */
    protected final Object _valueHandler;

    /**
     * Optional handler that can be attached to indicate how to handle
     * additional type metadata associated with this type.
     *

     * Note: untyped (i.e. caller has to cast) because it is used for
     * different kinds of handlers, with unrelated types.
     */
    protected final Object _typeHandler;
    
    /*
    /**********************************************************
    /* Life-cycle
    /**********************************************************
     */

    /**
     * @param raw "Raw" (type-erased) class for this type
     * @param additionalHash Additional hash code to use, in addition
     *   to hash code of the class name 
     */
    protected JavaType(Class raw, int additionalHash,
            Object valueHandler, Object typeHandler)
    {
        _class = raw;
        _hashCode = raw.getName().hashCode() + additionalHash;
        _valueHandler = valueHandler;
        _typeHandler = typeHandler;
    }

    /**
     * Serialization method called when no additional type information is
     * to be included in serialization.
     */
    
    /**
     * "Copy method" that will construct a new instance that is identical to
     * this instance, except that it will have specified type handler assigned.
     * 
     * @return Newly created type instance
     */
    public abstract JavaType withTypeHandler(Object h);

    /**
     * "Copy method" that will construct a new instance that is identical to
     * this instance, except that its content type will have specified
     * type handler assigned.
     * 
     * @return Newly created type instance
     */
    public abstract JavaType withContentTypeHandler(Object h);

    /**
     * "Copy method" that will construct a new instance that is identical to
     * this instance, except that it will have specified value handler assigned.
     * 
     * @return Newly created type instance
     */
    public abstract JavaType withValueHandler(Object h);

    /**
     * "Copy method" that will construct a new instance that is identical to
     * this instance, except that it will have specified content value handler assigned.
     * 
     * @return Newly created type instance
     */
    public abstract JavaType withContentValueHandler(Object h);
    
    /*
    /**********************************************************
    /* Type coercion fluent factory methods
    /**********************************************************
     */
    
    /**
     * Method that can be called to do a "narrowing" conversions; that is,
     * to return a type with a raw class that is assignable to the raw
     * class of this type. If this is not possible, an
     * {@link IllegalArgumentException} is thrown.
     * If class is same as the current raw class, instance itself is
     * returned.
     */
    public JavaType narrowBy(Class subclass)
    {
        // First: if same raw class, just return this instance
        if (subclass == _class) {
            return this;
        }
        // Otherwise, ensure compatibility
        _assertSubclass(subclass, _class);
        JavaType result = _narrow(subclass);

        // TODO: these checks should NOT actually be needed; above should suffice:
        if (_valueHandler != result.getValueHandler()) {
            result = result.withValueHandler(_valueHandler);
        }
        if (_typeHandler != result.getTypeHandler()) {
            result = result.withTypeHandler(_typeHandler);
        }
        return result;
    }

    /**
     * More efficient version of {@link #narrowBy}, called by
     * internal framework in cases where compatibility checks
     * are to be skipped.
     */
    public JavaType forcedNarrowBy(Class subclass)
    {
        if (subclass == _class) { // can still optimize for simple case
            return this;
        }
        JavaType result = _narrow(subclass);
        // TODO: these checks should NOT actually be needed; above should suffice:
        if (_valueHandler != result.getValueHandler()) {
            result = result.withValueHandler(_valueHandler);
        }
        if (_typeHandler != result.getTypeHandler()) {
            result = result.withTypeHandler(_typeHandler);
        }
        return result;
    }

    /**
     * Method that can be called to do a "widening" conversions; that is,
     * to return a type with a raw class that could be assigned from this
     * type.
     * If such conversion is not possible, an
     * {@link IllegalArgumentException} is thrown.
     * If class is same as the current raw class, instance itself is
     * returned.
     */
    public JavaType widenBy(Class superclass)
    {
        // First: if same raw class, just return this instance
        if (superclass == _class) {
            return this;
        }
        // Otherwise, ensure compatibility
        _assertSubclass(_class, superclass);
        return _widen(superclass);
    }

    protected abstract JavaType _narrow(Class subclass);

    /**
     *

     * Default implementation is just to call {@link #_narrow}, since
     * underlying type construction is usually identical
     */
    protected JavaType _widen(Class superclass) {
        return _narrow(superclass);
    }

    public abstract JavaType narrowContentsBy(Class contentClass);

    public abstract JavaType widenContentsBy(Class contentClass);
    
    /*
    /**********************************************************
    /* Implementation of ResolvedType API
    /**********************************************************
     */

    @Override
    public final Class getRawClass() { return _class; }

    /**
     * Method that can be used to check whether this type has
     * specified Class as its type erasure. Put another way, returns
     * true if instantiation of this Type is given (type-erased) Class.
     */
    @Override
    public final boolean hasRawClass(Class clz) {
        return _class == clz;
    }

    @Override
    public boolean isAbstract() {
        return Modifier.isAbstract(_class.getModifiers());
    }

    /**
     * Convenience method for checking whether underlying Java type
     * is a concrete class or not: abstract classes and interfaces
     * are not.
     */
    @Override
    public boolean isConcrete() {
        int mod = _class.getModifiers();
        if ((mod & (Modifier.INTERFACE | Modifier.ABSTRACT)) == 0) {
            return true;
        }
        /* 19-Feb-2010, tatus: Holy mackarel; primitive types
         *    have 'abstract' flag set...
         */
        if (_class.isPrimitive()) {
            return true;
        }
        return false;
    }

    @Override
    public boolean isThrowable() {
        return Throwable.class.isAssignableFrom(_class);
    }

    @Override
    public boolean isArrayType() { return false; }

    @Override
    public final boolean isEnumType() { return _class.isEnum(); }

    @Override
    public final boolean isInterface() { return _class.isInterface(); }

    @Override
    public final boolean isPrimitive() { return _class.isPrimitive(); }

    @Override
    public final boolean isFinal() { return Modifier.isFinal(_class.getModifiers()); }

    /**
     * @return True if type represented is a container type; this includes
     *    array, Map and Collection types.
     */
    @Override
    public abstract boolean isContainerType();

    /**
     * @return True if type is either true {@link java.util.Collection} type,
     *    or something similar (meaning it has at least one type parameter,
     *    which describes type of contents)
     */
    @Override
    public boolean isCollectionLikeType() { return false; }

    /**
     * @return True if type is either true {@link java.util.Map} type,
     *    or something similar (meaning it has at least two type parameter;
     *    first one describing key type, second value type)
     */
    @Override
    public boolean isMapLikeType() { return false; }
    
    /*
    /**********************************************************
    /* Public API, type parameter access; pass-through
    /**********************************************************
     */

    @Override
    public boolean hasGenericTypes()
    {
        return containedTypeCount() > 0;
    }

    @Override
    public JavaType getKeyType() { return null; }

    @Override
    public JavaType getContentType() { return null; }

    @Override
    public int containedTypeCount() { return 0; }

    @Override
    public JavaType containedType(int index) { return null; }

    @Override
    public String containedTypeName(int index) { return null; }

    /*
    /**********************************************************
    /* Semi-public API, accessing handlers
    /**********************************************************
     */
    
    /**
     * Method for accessing value handler associated with this type, if any
     */
    @SuppressWarnings("unchecked")
    public  T getValueHandler() { return (T) _valueHandler; }

    /**
     * Method for accessing type handler associated with this type, if any
     */
    @SuppressWarnings("unchecked")
    public  T getTypeHandler() { return (T) _typeHandler; }

    /*
    /**********************************************************
    /* Support for producing signatures
    /**********************************************************
     */
    
    //public abstract String toCanonical();

    /**
     * Method for accessing signature that contains generic
     * type information, in form compatible with JVM 1.5
     * as per JLS. It is a superset of {@link #getErasedSignature},
     * in that generic information can be automatically removed
     * if necessary (just remove outermost
     * angle brackets along with content inside)
     */
    public String getGenericSignature() {
        StringBuilder sb = new StringBuilder(40);
        getGenericSignature(sb);
        return sb.toString();        
    }

    /**
     * 
     * @param sb StringBuilder to append signature to
     * 
     * @return StringBuilder that was passed in; returned to allow
     * call chaining
     */
    public abstract StringBuilder getGenericSignature(StringBuilder sb);
    
    /**
     * Method for accessing signature without generic
     * type information, in form compatible with all versions
     * of JVM, and specifically used for type descriptions
     * when generating byte code.
     */
    public String getErasedSignature() {
        StringBuilder sb = new StringBuilder(40);
        getErasedSignature(sb);
        return sb.toString();
    }

    /**
     * Method for accessing signature without generic
     * type information, in form compatible with all versions
     * of JVM, and specifically used for type descriptions
     * when generating byte code.
     * 
     * @param sb StringBuilder to append signature to
     * 
     * @return StringBuilder that was passed in; returned to allow
     * call chaining
     */
    public abstract StringBuilder getErasedSignature(StringBuilder sb);
    
    /*
    /**********************************************************
    /* Helper methods
    /**********************************************************
     */

    protected void _assertSubclass(Class subclass, Class superClass)
    {
        if (!_class.isAssignableFrom(subclass)) {
            throw new IllegalArgumentException("Class "+subclass.getName()+" is not assignable to "+_class.getName());
        }
    }

    /*
    /**********************************************************
    /* Standard methods; let's make them abstract to force override
    /**********************************************************
     */

    @Override
    public abstract String toString();

    @Override
    public abstract boolean equals(Object o);

    @Override
    public final int hashCode() { return _hashCode; }
}
 















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