ctfield.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;

import javassist.bytecode.*;
import javassist.compiler.Javac;
import javassist.compiler.SymbolTable;
import javassist.compiler.CompileError;
import javassist.compiler.ast.ASTree;
import javassist.compiler.ast.IntConst;
import javassist.compiler.ast.DoubleConst;
import javassist.compiler.ast.StringL;

/**
 * An instance of CtField represents a field.
 *
 * @see CtClass#getDeclaredFields()
 */
public class CtField extends CtMember {
    static final String javaLangString = "java.lang.String";

    protected FieldInfo fieldInfo;

    /**
     * Creates a <code>CtField</code> object.
     * The created field must be added to a class
     * with <code>CtClass.addField()</code>.
     * An initial value of the field is specified
     * by a <code>CtField.Initializer</code> object.
     *
     * <p>If getter and setter methods are needed,
     * call <code>CtNewMethod.getter()</code> and 
     * <code>CtNewMethod.setter()</code>.
     *
     * @param type              field type
     * @param name              field name
     * @param declaring         the class to which the field will be added.
     *
     * @see CtClass#addField(CtField)
     * @see CtNewMethod#getter(String,CtField)
     * @see CtNewMethod#setter(String,CtField)
     * @see CtField.Initializer
     */
    public CtField(CtClass type, String name, CtClass declaring)
        throws CannotCompileException
    {
        this(Descriptor.of(type), name, declaring);
    }

    /**
     * Creates a copy of the given field.
     * The created field must be added to a class
     * with <code>CtClass.addField()</code>.
     * An initial value of the field is specified
     * by a <code>CtField.Initializer</code> object.
     *
     * <p>If getter and setter methods are needed,
     * call <code>CtNewMethod.getter()</code> and 
     * <code>CtNewMethod.setter()</code>.
     *
     * @param src               the original field
     * @param declaring         the class to which the field will be added.
     * @see CtNewMethod#getter(String,CtField)
     * @see CtNewMethod#setter(String,CtField)
     * @see CtField.Initializer
     */
    public CtField(CtField src, CtClass declaring)
        throws CannotCompileException
    {
        this(src.fieldInfo.getDescriptor(), src.fieldInfo.getName(),
             declaring);
        java.util.ListIterator iterator
            = src.fieldInfo.getAttributes().listIterator();
        FieldInfo fi = fieldInfo;
        fi.setAccessFlags(src.fieldInfo.getAccessFlags());
        ConstPool cp = fi.getConstPool();
        while (iterator.hasNext()) {
            AttributeInfo ainfo = (AttributeInfo)iterator.next();
            fi.addAttribute(ainfo.copy(cp, null));
        }
    }

    private CtField(String typeDesc, String name, CtClass clazz)
        throws CannotCompileException
    {
        super(clazz);
        next = null;
        ClassFile cf = clazz.getClassFile2();
        if (cf == null)
            throw new CannotCompileException("bad declaring class: "
                                             + clazz.getName());

        fieldInfo = new FieldInfo(cf.getConstPool(), name, typeDesc);
    }

    CtField(FieldInfo fi, CtClass clazz) {
        super(clazz);
        fieldInfo = fi;
        next = null;
    }

    /**
     * Returns a String representation of the object.
     */
    public String toString() {
        return getDeclaringClass().getName() + "." + getName()
               + ":" + fieldInfo.getDescriptor();
    }

    protected void extendToString(StringBuffer buffer) {
        buffer.append(' ');
        buffer.append(getName());
        buffer.append(' ');
        buffer.append(fieldInfo.getDescriptor());
    }

    /* Javac.CtFieldWithInit overrides.
     */
    protected ASTree getInitAST() { return null; }

    /* Called by CtClassType.addField().
     */
    Initializer getInit() {
        ASTree tree = getInitAST();
        if (tree == null)
            return null;
        else
            return Initializer.byExpr(tree);
    }

    /**
     * Compiles the given source code and creates a field.
     * Examples of the source code are:
     *
     * <ul><pre>
     * "public String name;"
     * "public int k = 3;"</pre></ul>
     *
     * <p>Note that the source code ends with <code>';'</code>
     * (semicolon).
     *
     * @param src               the source text.
     * @param declaring    the class to which the created field is added.
     */
    public static CtField make(String src, CtClass declaring)
        throws CannotCompileException
    {
        Javac compiler = new Javac(declaring);
        try {
            CtMember obj = compiler.compile(src);
            if (obj instanceof CtField)
                return (CtField)obj; // an instance of Javac.CtFieldWithInit
        }
        catch (CompileError e) {
            throw new CannotCompileException(e);
        }

        throw new CannotCompileException("not a field");
    }

    /**
     * Returns the FieldInfo representing the field in the class file.
     */
    public FieldInfo getFieldInfo() {
        declaringClass.checkModify();
        return fieldInfo;
    }

    /**
     * Returns the FieldInfo representing the field in the class
     * file (read only).
     * Normal applications do not need calling this method.  Use
     * <code>getFieldInfo()</code>.
     *
     * <p>The <code>FieldInfo</code> object obtained by this method
     * is read only.  Changes to this object might not be reflected
     * on a class file generated by <code>toBytecode()</code>,
     * <code>toClass()</code>, etc in <code>CtClass</code>.
     *
     * <p>This method is available even if the <code>CtClass</code>
     * containing this field is frozen.  However, if the class is
     * frozen, the <code>FieldInfo</code> might be also pruned.
     *
     * @see #getFieldInfo()
     * @see CtClass#isFrozen()
     * @see CtClass#prune()
     */
    public FieldInfo getFieldInfo2() { return fieldInfo; }

    /**
     * Returns the class declaring the field.
     */
    public CtClass getDeclaringClass() {
        // this is redundant but for javadoc.
        return super.getDeclaringClass();
    }

    /**
     * Returns the name of the field.
     */
    public String getName() {
        return fieldInfo.getName();
    }

    /**
     * Changes the name of the field.
     */
    public void setName(String newName) {
        declaringClass.checkModify();
        fieldInfo.setName(newName);
    }

    /**
     * Returns the encoded modifiers of the field.
     *
     * @see Modifier
     */
    public int getModifiers() {
        return AccessFlag.toModifier(fieldInfo.getAccessFlags());
    }

    /**
     * Sets the encoded modifiers of the field.
     *
     * @see Modifier
     */
    public void setModifiers(int mod) {
        declaringClass.checkModify();
        fieldInfo.setAccessFlags(AccessFlag.of(mod));
    }

    /**
     * Returns the annotations associated with this field.
     *
     * @return an array of annotation-type objects.
     * @see #getAvailableAnnotations()
     * @since 3.1
     */
    public Object[] getAnnotations() throws ClassNotFoundException {
        return getAnnotations(false);
    }

    /**
     * Returns the annotations associated with this field.
     * If any annotations are not on the classpath, they are not included
     * in the returned array.
     *
     * @return an array of annotation-type objects.
     * @see #getAnnotations()
     * @since 3.3
     */
    public Object[] getAvailableAnnotations(){
        try {
            return getAnnotations(true);
        }
        catch (ClassNotFoundException e) {
           throw new RuntimeException("Unexpected exception", e);
        }
    }

    private Object[] getAnnotations(boolean ignoreNotFound) throws ClassNotFoundException {
        FieldInfo fi = getFieldInfo2();
        AnnotationsAttribute ainfo = (AnnotationsAttribute)
                    fi.getAttribute(AnnotationsAttribute.invisibleTag);  
        AnnotationsAttribute ainfo2 = (AnnotationsAttribute)
                    fi.getAttribute(AnnotationsAttribute.visibleTag);  
        return CtClassType.toAnnotationType(ignoreNotFound, getDeclaringClass().getClassPool(),
                                            ainfo, ainfo2);
    }

    /**
     * Returns the character string representing the type of the field.
     * If two fields have the same type,
     * <code>getSignature()</code> returns the same string.
     */
    public String getSignature() {
        return fieldInfo.getDescriptor();
    }

    /**
     * Returns the type of the field.
     */
    public CtClass getType() throws NotFoundException {
        return Descriptor.toCtClass(fieldInfo.getDescriptor(),
                                    declaringClass.getClassPool());
    }

    /**
     * Sets the type of the field.
     */
    public void setType(CtClass clazz) {
        declaringClass.checkModify();
        fieldInfo.setDescriptor(Descriptor.of(clazz));
    }

    /**
     * Returns the value of this field if it is a constant field.
     * This method works only if the field type is a primitive type
     * or <code>String</code> type.  Otherwise, it returns <code>null</code>.
     * A constant field is <code>static</code> and <code>final</code>.
     *
     * @return  a <code>Integer</code>, <code>Long</code>, <code>Float</code>,
     *          <code>Double</code>, <code>Boolean</code>,
     *          or <code>String</code> object
     *          representing the constant value. 
     *          <code>null</code> if it is not a constant field
     *          or if the field type is not a primitive type
     *          or <code>String</code>.
     */
    public Object getConstantValue() {
        // When this method is modified,
        // see also getConstantFieldValue() in TypeChecker.

        int index = fieldInfo.getConstantValue();
        if (index == 0)
            return null;

        ConstPool cp = fieldInfo.getConstPool();
        switch (cp.getTag(index)) {
            case ConstPool.CONST_Long :
                return new Long(cp.getLongInfo(index));
            case ConstPool.CONST_Float :
                return new Float(cp.getFloatInfo(index));
            case ConstPool.CONST_Double :
                return new Double(cp.getDoubleInfo(index));
            case ConstPool.CONST_Integer :
                int value = cp.getIntegerInfo(index);
                // "Z" means boolean type.
                if ("Z".equals(fieldInfo.getDescriptor()))
                    return new Boolean(value != 0);
                else
                    return new Integer(value);
            case ConstPool.CONST_String :
                return cp.getStringInfo(index);
            default :
                throw new RuntimeException("bad tag: " + cp.getTag(index)
                                           + " at " + index);
        }
    }

    /**
     * Obtains an attribute with the given name.
     * If that attribute is not found in the class file, this
     * method returns null.
     *
     * <p>Note that an attribute is a data block specified by
     * the class file format.
     * See {@link javassist.bytecode.AttributeInfo}.
     *
     * @param name              attribute name
     */
    public byte[] getAttribute(String name) {
        AttributeInfo ai = fieldInfo.getAttribute(name);
        if (ai == null)
            return null;
        else
            return ai.get();
    }

    /**
     * Adds an attribute. The attribute is saved in the class file.
     *
     * <p>Note that an attribute is a data block specified by
     * the class file format.
     * See {@link javassist.bytecode.AttributeInfo}.
     *
     * @param name      attribute name
     * @param data      attribute value
     */
    public void setAttribute(String name, byte[] data) {
        declaringClass.checkModify();
        fieldInfo.addAttribute(new AttributeInfo(fieldInfo.getConstPool(),
                                                 name, data));
    }

    // inner classes

    /**
     * Instances of this class specify how to initialize a field.
     * <code>Initializer</code> is passed to
     * <code>CtClass.addField()</code> with a <code>CtField</code>.
     *
     * <p>This class cannot be instantiated with the <code>new</code> operator.
     * Factory methods such as <code>byParameter()</code> and
     * <code>byNew</code>
     * must be used for the instantiation.  They create a new instance with
     * the given parameters and return it.
     *
     * @see CtClass#addField(CtField,CtField.Initializer)
     */
    public static abstract class Initializer {
        /**
         * Makes an initializer that assigns a constant integer value.
         * The field must be integer type.
         */
        public static Initializer constant(int i) {
            return new IntInitializer(i);
        }

        /**
         * Makes an initializer that assigns a constant long value.
         * The field must be long type.
         */
        public static Initializer constant(long l) {
            return new LongInitializer(l);
        }

        /**
         * Makes an initializer that assigns a constant double value.
         * The field must be double type.
         */
        public static Initializer constant(double d) {
            return new DoubleInitializer(d);
        }

        /**
         * Makes an initializer that assigns a constant string value.
         * The field must be <code>java.lang.String</code> type.
         */