[micro service sentinel] rewrite Sentinel's interface blockexceptionhandler

Above, , We use sentinel Integrate feign, Let it be in feign The client handles exceptions uniformly , The principle is that when one service calls another service , If an exception is detected BlockExceptionHandler, Use the bottom covering method to deal with .

Source code

Let's have a look BlockExceptionHandler Source code ：

public interface BlockExceptionHandler {
    

    void handle(HttpServletRequest request, HttpServletResponse response, BlockException e) throws Exception;

}

Oh , It turned out to be an interface .

Realization

Let's take a look at the implementation classes , Just a default , ok .

public class DefaultBlockExceptionHandler implements BlockExceptionHandler {
    

    @Override
    public void handle(HttpServletRequest request, HttpServletResponse response, BlockException e) throws Exception {
    
        // Return 429 (Too Many Requests) by default.
        response.setStatus(429);

        PrintWriter out = response.getWriter();
        out.print("Blocked by Sentinel (flow limiting)");
        out.flush();
        out.close();
    }
}

rewrite

This mistake is familiar , If we want to customize the current limiting return format and the information we need to return can distinguish various current limiting exceptions , We need to rewrite BlockExceptionHandler Interface , such as ：

import com.alibaba.csp.sentinel.adapter.spring.webmvc.callback.BlockExceptionHandler;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import com.alibaba.csp.sentinel.slots.block.authority.AuthorityException;
import com.alibaba.csp.sentinel.slots.block.degrade.DegradeException;
import com.alibaba.csp.sentinel.slots.block.flow.FlowException;
import com.alibaba.csp.sentinel.slots.block.flow.param.ParamFlowException;
import com.alibaba.csp.sentinel.slots.system.SystemBlockException;
import com.alibaba.fastjson.JSON;
import org.springframework.stereotype.Component;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

/** * @author issavior */
@Component
public class MyUrlBlockHandler implements BlockExceptionHandler {
    
    @Override
    public void handle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, BlockException e) throws IOException {
    
        Map<String,Object> backMap=new HashMap<>(16);
        if (e instanceof FlowException){
    
            backMap.put("code",-1);
            backMap.put("msg"," Current limiting - It's abnormal ");
        }else if (e instanceof DegradeException){
    
            backMap.put("code",-2);
            backMap.put("msg"," Downgrade - It's abnormal ");
        }else if (e instanceof ParamFlowException){
    
            backMap.put("code",-3);
            backMap.put("msg"," hotspot - It's abnormal ");
        }else if (e instanceof SystemBlockException){
    
            backMap.put("code",-4);
            backMap.put("msg"," System rules - It's abnormal ");
        }else if (e instanceof AuthorityException){
    
            backMap.put("code",-5);
            backMap.put("msg"," authentication - It's abnormal ");
        }
        //  Set back json data 
        httpServletResponse.setStatus(200);
        httpServletResponse.setHeader("content-Type","application/json;charset=UTF-8");
        httpServletResponse.getWriter().write(JSON.toJSONString(backMap));
    }
}

Problems and Solutions

But it's been tested , Find out , Hot spot current limiting is not easy to use , Then use the global exception to intercept , Ha ha ha , If you know the reason or have a better way , Remember to leave a message ～

import com.alibaba.csp.sentinel.slots.block.flow.param.ParamFlowException;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

/** * @author issavior */
@RestControllerAdvice
public class MyParamFlowException {
    

    @ExceptionHandler(ParamFlowException.class)
    public void test(HttpServletResponse response) throws IOException {
    
        response.setCharacterEncoding("UTF-8");
        response.setStatus(400);

        PrintWriter out = response.getWriter();
        out.print(" Trigger hot spot current limiting ");
        out.flush();
        out.close();
    }
}