Method.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.apache.bcel.classfile;

import java.io.DataInput;
import java.io.IOException;
import java.util.Objects;

import org.apache.bcel.generic.Type;
import org.apache.bcel.util.BCELComparator;

/**
 * This class represents the method info structure, i.e., the representation for a method in the class. See JVM
 * specification for details. A method has access flags, a name, a signature and a number of attributes.
 */
public final class Method extends FieldOrMethod {

    /**
     * Empty array constant.
     *
     * @since 6.6.0
     */
    public static final Method[] EMPTY_ARRAY = {};

    private static BCELComparator<Method> bcelComparator = new BCELComparator<Method>() {

        @Override
        public boolean equals(final Method a, final Method b) {
            return a == b || a != null && b != null && Objects.equals(a.getName(), b.getName()) && Objects.equals(a.getSignature(), b.getSignature());
        }

        @Override
        public int hashCode(final Method o) {
            return o != null ? Objects.hash(o.getSignature(), o.getName()) : 0;
        }
    };

    /**
     * @return Comparison strategy object.
     */
    public static BCELComparator<Method> getComparator() {
        return bcelComparator;
    }

    /**
     * @param comparator Comparison strategy object.
     */
    public static void setComparator(final BCELComparator<Method> comparator) {
        bcelComparator = comparator;
    }

    /** Annotations defined on the parameters of a method. */
    private ParameterAnnotationEntry[] parameterAnnotationEntries;

    /**
     * Empty constructor, all attributes have to be defined via 'setXXX' methods. Use at your own risk.
     */
    public Method() {
    }

    /**
     * Constructs object from file stream.
     *
     * @param file Input stream
     * @throws IOException if an I/O error occurs.
     * @throws ClassFormatException if a class is malformed or cannot be interpreted as a class file
     */
    Method(final DataInput file, final ConstantPool constantPool) throws IOException, ClassFormatException {
        super(file, constantPool);
    }

    /**
     * @param accessFlags Access rights of method
     * @param nameIndex Points to field name in constant pool
     * @param signatureIndex Points to encoded signature
     * @param attributes Collection of attributes
     * @param constantPool Array of constants
     */
    public Method(final int accessFlags, final int nameIndex, final int signatureIndex, final Attribute[] attributes, final ConstantPool constantPool) {
        super(accessFlags, nameIndex, signatureIndex, attributes, constantPool);
    }

    /**
     * Initialize from another object. Note that both objects use the same references (shallow copy). Use clone() for a
     * physical copy.
     *
     * @param c Source to copy.
     */
    public Method(final Method c) {
        super(c);
    }

    /**
     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
     *
     * @param v Visitor object
     */
    @Override
    public void accept(final Visitor v) {
        v.visitMethod(this);
    }

    /**
     * @return deep copy of this method
     */
    public Method copy(final ConstantPool constantPool) {
        return (Method) copy_(constantPool);
    }

    /**
     * Return value as defined by given BCELComparator strategy. By default two method objects are said to be equal when
     * their names and signatures are equal.
     *
     * @see Object#equals(Object)
     */
    @Override
    public boolean equals(final Object obj) {
        return obj instanceof Method && bcelComparator.equals(this, (Method) obj);
    }

    /**
     * @return array of method argument types
     */
    public Type[] getArgumentTypes() {
        return Type.getArgumentTypes(getSignature());
    }

    /**
     * @return Code attribute of method, if any
     */
    public Code getCode() {
        for (final Attribute attribute : super.getAttributes()) {
            if (attribute instanceof Code) {
                return (Code) attribute;
            }
        }
        return null;
    }

    /**
     * @return ExceptionTable attribute of method, if any, i.e., list all exceptions the method may throw not exception
     *         handlers!
     */
    public ExceptionTable getExceptionTable() {
        for (final Attribute attribute : super.getAttributes()) {
            if (attribute instanceof ExceptionTable) {
                return (ExceptionTable) attribute;
            }
        }
        return null;
    }

    /**
     * @return LineNumberTable of code attribute if any, i.e. the call is forwarded to the Code atribute.
     */
    public LineNumberTable getLineNumberTable() {
        final Code code = getCode();
        if (code == null) {
            return null;
        }
        return code.getLineNumberTable();
    }

    /**
     * @return LocalVariableTable of code attribute if any, i.e. the call is forwarded to the Code attribute.
     */
    public LocalVariableTable getLocalVariableTable() {
        final Code code = getCode();
        if (code == null) {
            return null;
        }
        return code.getLocalVariableTable();
    }

    /**
     * Gets the local variable type table attribute {@link LocalVariableTypeTable}.
     * @return LocalVariableTypeTable of code attribute if any, i.e. the call is forwarded to the Code attribute.
     * @since 6.10.0
     */
    public LocalVariableTypeTable getLocalVariableTypeTable() {
        final Code code = getCode();
        if (code == null) {
            return null;
        }
        return code.getLocalVariableTypeTable();
    }

    /**
     * @return Annotations on the parameters of a method
     * @since 6.0
     */
    public ParameterAnnotationEntry[] getParameterAnnotationEntries() {
        if (parameterAnnotationEntries == null) {
            parameterAnnotationEntries = ParameterAnnotationEntry.createParameterAnnotationEntries(getAttributes());
        }
        return parameterAnnotationEntries;
    }

    /**
     * @return return type of method
     */
    public Type getReturnType() {
        return Type.getReturnType(getSignature());
    }

    /**
     * Return value as defined by given BCELComparator strategy. By default return the hash code of the method's name XOR
     * signature.
     *
     * @see Object#hashCode()
     */
    @Override
    public int hashCode() {
        return bcelComparator.hashCode(this);
    }

    /**
     * Return string representation close to declaration format, 'public static void main(String[] args) throws
     * IOException', e.g.
     *
     * @return String representation of the method.
     */
    @Override
    public String toString() {
        final String access = Utility.accessToString(super.getAccessFlags());
        // Get name and signature from constant pool
        ConstantUtf8 c = super.getConstantPool().getConstantUtf8(super.getSignatureIndex());
        String signature = c.getBytes();
        c = super.getConstantPool().getConstantUtf8(super.getNameIndex());
        final String name = c.getBytes();
        signature = Utility.methodSignatureToString(signature, name, access, true, getLocalVariableTable());
        final StringBuilder buf = new StringBuilder(signature);
        for (final Attribute attribute : super.getAttributes()) {
            if (!(attribute instanceof Code || attribute instanceof ExceptionTable)) {
                buf.append(" [").append(attribute).append("]");
            }
        }
        final ExceptionTable e = getExceptionTable();
        if (e != null) {
            final String str = e.toString();
            if (!str.isEmpty()) {
                buf.append("\n\t\tthrows ").append(str);
            }
        }
        return buf.toString();
    }
}