spring boot 2 全局統一返回RESTful風格數據、統一異常處理

全局統一返回RESTful風格數據，主要是實現ResponseBodyAdvice接口的方法，對返回值在輸出以前進行修改。
使用註解@RestControllerAdvice攔截異常並統一處理。

開發環境：
IntelliJ IDEA 2019.2.2
jdk1.8
Spring Boot 2.2.2

一、建立一個SpringBoot項目，pom.xml引用的依賴包以下

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.62</version>
        </dependency>

二、定義一個返回類

package com.example.response.entity;

import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;

import java.io.Serializable;

@Data
@NoArgsConstructor
@ToString
public class ResponseData<T> implements Serializable {
    /**
     * 狀態碼：0-成功，1-失敗
     * */
    private int code;

    /**
     * 錯誤消息，若是成功可爲空或SUCCESS
     * */
    private String msg;

    /**
     * 返回結果數據
     * */
    private T data;

    public static ResponseData success() {
        return success(null);
    }

    public static ResponseData success(Object data) {
        ResponseData result = new ResponseData();
        result.setCode(0);
        result.setMsg("SUCCESS");
        result.setData(data);
        return result;
    }

    public static ResponseData fail(String msg) {
        return fail(msg,null);
    }

    public static ResponseData fail(String msg, Object data) {
        ResponseData result = new ResponseData();
        result.setCode(1);
        result.setMsg(msg);
        result.setData(data);
        return result;
    }
}

三、統一攔截接口返回數據

新建一個類GlobalResponseHandler，用註解@RestControllerAdvice，而且實現ResponseBodyAdvice接口的方法，其中方法supports能夠判斷哪些須要攔截，方法beforeBodyWrite能夠對返回值在輸出以前進行修改，從而實現返回統一的接口數據。

package com.example.response.config;

import com.alibaba.fastjson.JSON;
import com.example.response.entity.ResponseData;
import org.springframework.core.MethodParameter;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.web.bind.annotation.RestControllerAdvice;
import org.springframework.web.servlet.mvc.method.annotation.ResponseBodyAdvice;

/**
 * 實現ResponseBodyAdvice接口，能夠對返回值在輸出以前進行修改
 */
@RestControllerAdvice
public class GlobalResponseHandler implements ResponseBodyAdvice<Object> {

    //判斷支持的類型
    @Override
    public boolean supports(MethodParameter methodParameter, Class<? extends HttpMessageConverter<?>> aClass) {
        // 檢查註解是否存在，存在則忽略攔截
        if (methodParameter.getDeclaringClass().isAnnotationPresent(IgnorReponseAdvice.class)) {
            return false;
        }
        if (methodParameter.getMethod().isAnnotationPresent(IgnorReponseAdvice.class)) {
            return false;
        }
        return true;
    }

    @Override
    public Object beforeBodyWrite(Object o, MethodParameter methodParameter, MediaType mediaType, Class<? extends HttpMessageConverter<?>> aClass, ServerHttpRequest serverHttpRequest, ServerHttpResponse serverHttpResponse) {
        // 判斷爲null構建ResponseData對象進行返回
        if (o == null) {
            return ResponseData.success();
        }
        // 判斷是ResponseData子類或其自己就返回Object o自己，由於有多是接口返回時建立了ResponseData,這裏避免再次封裝
        if (o instanceof ResponseData) {
            return (ResponseData<Object>) o;
        }
        // String特殊處理，不然會拋異常
        if (o instanceof String) {
            return JSON.toJSON(ResponseData.success(o)).toString();
        }
        return ResponseData.success(o);
    }
}

新建自定義註解IgnorReponseAdvice

package com.example.response.config;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface IgnorReponseAdvice {
}

四、統一異常處理

package com.example.response.exception;
import com.example.response.entity.ResponseData;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;

@RestControllerAdvice
public class GlobalExceptionHandler {
    @ExceptionHandler(Exception.class)
    public ResponseData exceptionHandler(Exception e) {
        e.printStackTrace();
        return ResponseData.fail("服務器異常：" + e.getMessage());
    }
}

五、新建一個測試用的實體類

package com.example.response.entity;

import lombok.Data;

@Data
public class User {
    private Long userId;
    private String userName;
    public User(Long userId, String userName){
        this.userId = userId;
        this.userName = userName;
    }
}

六、新建一個測試用的控制器類

package com.example.response.controller;

import com.example.response.config.IgnorReponseAdvice;
import com.example.response.entity.ResponseData;
import com.example.response.entity.User;
import org.springframework.web.bind.annotation.*;

import java.util.ArrayList;
import java.util.List;

@RestController
public class DemoController {
    @GetMapping("user")
    public User user() {
        User u = new User(100L, "u1");
        return u;
    }

    @GetMapping("userList")
    public List<User> userList(){
        List<User> list = new ArrayList<User>();
        list.add(new User(100L, "u1"));
        list.add(new User(200L, "u2"));
        return list;
    }

    @GetMapping("test1")
    public String test1(){
        return "test1";
    }

    @GetMapping("test2")
    public ResponseData test2(){
        return ResponseData.success("test2");
    }

    @IgnorReponseAdvice
    @GetMapping("test3")
    public String test3() {
        return "test3";
    }

    @GetMapping("test4")
    public String test4() {
        Integer x = 1 / 0;
        return x.toString();
    }

    @GetMapping("test5")
    public String test5() throws Exception {
        throw new Exception("自定義異常信息");
    }
}

七、用Postman測試

(1)請求http://localhost:8080/user，返回

{
    "code": 0,
    "msg": "SUCCESS",
    "data": {
        "userId": 100,
        "userName": "u1"
    }
}

(2)請求http://localhost:8080/userList，返回

{
    "code": 0,
    "msg": "SUCCESS",
    "data": [
        {
            "userId": 100,
            "userName": "u1"
        },
        {
            "userId": 200,
            "userName": "u2"
        }
    ]
}

(3)請求http://localhost:8080/tes1，返回

{"msg":"SUCCESS","code":0,"data":"test1"}

(4)請求http://localhost:8080/test2，返回

{
    "code": 0,
    "msg": "SUCCESS",
    "data": "test2"
}

(5)請求http://localhost:8080/test3，返回

test3

(6)請求http://localhost:8080/test4，返回

{
    "code": 1,
    "msg": "服務器異常：/ by zero",
    "data": null
}

(7)請求http://localhost:8080/test5，返回

{
    "code": 1,
    "msg": "服務器異常：自定義異常信息",
    "data": null
}

  

參考文章：
https://blog.csdn.net/lrt890424/article/details/83624761
http://www.javashuo.com/article/p-pdgkpnsi-mx.html