Javassist：在catch块的开头插入一个方法 [英] Javassist: insert a method at the beginning of catch block

问题描述

我有代码：

ControlFlow cf = new ControlFlow(method);

for (ControlFlow.Block block : cf.basicBlocks()) {
   ControlFlow.Catcher catchBlocks[] = block.catchers();
   for (int i = 0;i < catchBlocks.length;i++) {
      int position = catchBlocks[i].block().position();
      method.insertAt(position, "System.out.println(\"catch block\")")
   }    
}

此代码段将print语句插入方法的开头，这不是我想要的。我希望将代码放置为：

This code snippet inserts the print statement at beginning of the method, which is not what I want. I want the code to be placed like:

void foo() {
    try {
        a();
    } catch(Exception e) {
        System.out.println("catch block");//inserted by javassist
        b();
    }
}

你知道我的代码哪里写错了吗？

Any idea where my code got wrong?

一种更优雅的处理方式

 CtBehavior.instrument(new ExprEditor() {
            @Override
            public void edit(Handler h) throws CannotCompileException {
                if( !h.isFinally()) {
                    h.insertBefore("System.out.println(\"catch block\")");
                }
            }
        });

参考： http://www.javassist.org/tutorial/tutorial2.html#intro

推荐答案

您应该尝试在要查找的块的源代码中获取行号。

You should try to get the line number in the source code of the block you are looking for.

尝试

ControlFlow cf = new ControlFlow(method);

for (ControlFlow.Block block : cf.basicBlocks()) {
   ControlFlow.Catcher catchBlocks[] = block.catchers();
   for (int i = 0;i < catchBlocks.length;i++) {
      int position = catchBlocks[i].block().position();
      // Get source code line position 
      int lineNumber = method.getMethodInfo().getLineNumber(position ); 
      method.insertAt(lineNumber+1 , "System.out.println(\"catch block\")")
   }    
}

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