co.cask.cdap.internal.asm.FinallyAdapter.java Source code

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Here is the source code for co.cask.cdap.internal.asm.FinallyAdapter.java

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/*
 * Copyright  2016 Cask Data, Inc.
 *
 * Licensed 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 co.cask.cdap.internal.asm;

import org.objectweb.asm.Label;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.commons.AdviceAdapter;

/**
 * A {@link MethodVisitor} that wraps method call with {@code try-finally} block.
 * Sub-class can override the {@link #onFinally(int)} method to insert custom code in the finally block.
 */
public class FinallyAdapter extends AdviceAdapter {

    private final Label startFinally = new Label();

    protected FinallyAdapter(int api, MethodVisitor mv, int access, String name, String desc) {
        super(api, mv, access, name, desc);
    }

    @Override
    public void visitMaxs(int maxStack, int maxLocals) {
        Label endFinally = new Label();
        mv.visitTryCatchBlock(startFinally, endFinally, endFinally, null);
        mv.visitLabel(endFinally);

        // this is essentially catching exception, invoke the finally code block and rethrow the exception
        onFinally(ATHROW);
        mv.visitInsn(ATHROW);
        mv.visitMaxs(maxStack, maxLocals);
    }

    @Override
    protected void onMethodExit(int opcode) {
        if (opcode != ATHROW) {
            onFinally(opcode);
        }
    }

    /**
     * Sub-class should call this to signal the beginning of the try block.
     */
    protected void beginTry() {
        mv.visitLabel(startFinally);
    }

    /**
     * Calls to generate code for the finally block.
     */
    protected void onFinally(int opcode) {
        // No-op
    }
}