parameterannotationsattribute.java

Javassist是一个开源的分析、编辑和创建Java字节码的类库。是由东京技术学院的数学和计算机科学系的 Shigeru Chiba 所创建的。它已加入了开放源代码JBoss 应用服务器项目,通过使

/*
 * Javassist, a Java-bytecode translator toolkit.
 * Copyright (C) 1999-2006 Shigeru Chiba. All Rights Reserved.
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License.  Alternatively, the contents of this file may be used under
 * the terms of the GNU Lesser General Public License Version 2.1 or later.
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 */

package javassist.bytecode;

import java.util.Map;
import java.io.IOException;
import java.io.DataInputStream;
import java.io.ByteArrayOutputStream;

import javassist.bytecode.AnnotationsAttribute.Copier;
import javassist.bytecode.AnnotationsAttribute.Parser;
import javassist.bytecode.annotation.*;

/**
 * A class representing <code>RuntimeVisibleAnnotations_attribute</code> and
 * <code>RuntimeInvisibleAnnotations_attribute</code>.
 *
 * <p>To obtain an ParameterAnnotationAttribute object, invoke
 * <code>getAttribute(ParameterAnnotationsAttribute.invisibleTag)</code>
 * in <code>MethodInfo</code>.
 * The obtained attribute is a
 * runtime invisible annotations attribute.  
 * If the parameter is
 * <code>ParameterAnnotationAttribute.visibleTag</code>, then the obtained
 * attribute is a runtime visible one.
 */
public class ParameterAnnotationsAttribute extends AttributeInfo {
    /**
     * The name of the <code>RuntimeVisibleParameterAnnotations</code>
     * attribute.
     */
    public static final String visibleTag
        = "RuntimeVisibleParameterAnnotations";

    /**
     * The name of the <code>RuntimeInvisibleParameterAnnotations</code>
     * attribute.
     */
    public static final String invisibleTag
        = "RuntimeInvisibleParameterAnnotations";
    /**
     * Constructs
     * a <code>Runtime(In)VisisbleParameterAnnotations_attribute</code>.
     *
     * @param cp            constant pool
     * @param attrname      attribute name (<code>visibleTag</code> or
     *                      <code>invisibleTag</code>).
     * @param info          the contents of this attribute.  It does not
     *                      include <code>attribute_name_index</code> or
     *                      <code>attribute_length</code>.
     */
    public ParameterAnnotationsAttribute(ConstPool cp, String attrname,
                                         byte[] info) {
        super(cp, attrname, info);
    }

    /**
     * Constructs an empty
     * <code>Runtime(In)VisisbleParameterAnnotations_attribute</code>.
     * A new annotation can be later added to the created attribute
     * by <code>setAnnotations()</code>.
     *
     * @param cp            constant pool
     * @param attrname      attribute name (<code>visibleTag</code> or
     *                      <code>invisibleTag</code>).
     * @see #setAnnotations(Annotation[][])
     */
    public ParameterAnnotationsAttribute(ConstPool cp, String attrname) {
        this(cp, attrname, new byte[] { 0 });
    }

    /**
     * @param n     the attribute name.
     */
    ParameterAnnotationsAttribute(ConstPool cp, int n, DataInputStream in)
        throws IOException
    {
        super(cp, n, in);
    }

    /**
     * Returns <code>num_parameters</code>. 
     */
    public int numParameters() {
        return info[0] & 0xff;
    }

    /**
     * Copies this attribute and returns a new copy.
     */
    public AttributeInfo copy(ConstPool newCp, Map classnames) {
        Copier copier = new Copier(info, constPool, newCp, classnames);
        try {
            copier.parameters();
            return new ParameterAnnotationsAttribute(newCp, getName(),
                                                     copier.close());
        }
        catch (Exception e) {
            throw new RuntimeException(e.toString());
        }
    }

    /**
     * Parses the annotations and returns a data structure representing
     * that parsed annotations.  Note that changes of the node values of the
     * returned tree are not reflected on the annotations represented by
     * this object unless the tree is copied back to this object by
     * <code>setAnnotations()</code>.
     *
     * @return Each element of the returned array represents an array of
     * annotations that are associated with each method parameter.
     *      
     * @see #setAnnotations(Annotation[][])
     */
    public Annotation[][] getAnnotations() {
        try {
            return new Parser(info, constPool).parseParameters();
        }
        catch (Exception e) {
            throw new RuntimeException(e.toString());
        }
    }

    /**
     * Changes the annotations represented by this object according to
     * the given array of <code>Annotation</code> objects.
     *
     * @param params        the data structure representing the
     *                      new annotations. Every element of this array
     *                      is an array of <code>Annotation</code> and
     *                      it represens annotations of each method parameter.
     */
    public void setAnnotations(Annotation[][] params) {
        ByteArrayOutputStream output = new ByteArrayOutputStream();
        AnnotationsWriter writer = new AnnotationsWriter(output, constPool);
        try {
            int n = params.length;
            writer.numParameters(n);
            for (int i = 0; i < n; ++i) {
                Annotation[] anno = params[i];
                writer.numAnnotations(anno.length);
                for (int j = 0; j < anno.length; ++j)
                    anno[j].write(writer);
            }

            writer.close();
        }
        catch (IOException e) {
            throw new RuntimeException(e);      // should never reach here.
        }

        set(output.toByteArray());
    }
}