Issue description

setBody not work

Environment

• your apisix-java-plugin-runner version
  0.2.0

Minimal test code / Steps to reproduce the issue

1. I want to set Request Body like request.setBody("h=xxxxxx") or request.setBody("{"hello":"23f"}")
2. But the real server still get the orginal request body.
   我想通过setBody设置request body。但是不ok。获取得到的还是原先的request body。

What's the actual result? (including assertion message & call stack if applicable)

Get the orginal content

What's the expected result?

Get the setBody content