Question

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\")")
   }    
}

此代码段在方法的开头插入了打印语句，这不是我想要的。我希望将代码放置为：

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

知道我的代码哪里出错了吗？

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

Answer 1

您应该尝试在要查找的块的源代码中获取行号。

尝试如下所示：

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\")")
   }    
}

Javassist：在catch块的开头插入一个方法

1 个答案: