今天讲解一下如何在SpringBoot实现全局异常机制,在没有用springboot大家要实现这一的功能基本上都是通过aop的思想,还是有点麻烦，而现在springboot中对它要进行了一次封装,开发者使用起来更加的简单,接下先通过代码演示效果,然后再分析一下原理,好了废话不多说直接上代码,看代码结构:

看一下对应的Pom.xml文件内容:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <artifactId>spring_boot_exception</artifactId>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.2.RELEASE</version>
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>


    <dependencies>
        <!--  -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.16.18</version>
        </dependency>


        <!-- https://mvnrepository.com/artifact/com.alibaba/fastjson -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.44</version>
        </dependency>

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

    </dependencies>
</project>

定义一个封装json的工具类,使用阿里巴巴的fastjson：

package com.springboot.exception.json;

import com.alibaba.fastjson.JSON;
import lombok.Data;

import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;

/**
 * lombok格式化数据
 */
@Data
public class JsonResult implements Serializable{
 
    private int code;   //返回码 非0即失败
    private String msg; //消息提示
    private Map<String, Object> data; //返回的数据
 
    public JsonResult(){};
 
    public JsonResult(int code, String msg, Map<String, Object> data) {
        this.code = code;
        this.msg = msg;
        this.data = data;
    }
 
    public static String success() {
        return success(new HashMap(0));
    }
    public static String success(Map<String, Object> data) {
        return JSON.toJSONString(new JsonResult(0, "解析成功", data));
    }
 
    public static String failed() {
        return failed("解析失败");
    }
    public static String failed(String msg) {
        return failed(-1, msg);
    }
    public static String failed(int code, String msg) {
        return JSON.toJSONString(new JsonResult(code, msg, new HashMap(0)));
    }
 
}

接下来定义一个全局异常处理类:

package com.springboot.exception.global_excep;

import com.springboot.exception.json.JsonResult;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.ConversionNotSupportedException;
import org.springframework.beans.TypeMismatchException;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;
import org.springframework.web.HttpMediaTypeNotAcceptableException;
import org.springframework.web.HttpRequestMethodNotSupportedException;
import org.springframework.web.bind.MissingServletRequestParameterException;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;

import java.io.IOException;

/**
 * @Author 18011618
 * @Description 全局异常拦截器
 * @Date 16:38 2018/7/5
 * @Modify By
 */
@ControllerAdvice
@ResponseBody
public class GlobalExceptionHandler {

    private static final String logExceptionFormat = "Capture Exception By GlobalExceptionHandler: Code: %s Detail: %s";
    private static Logger log = LoggerFactory.getLogger(GlobalExceptionHandler.class);

    //运行时异常
    @ExceptionHandler(RuntimeException.class)
    public String runtimeExceptionHandler(RuntimeException ex) {
        return resultFormat(1, ex);
    }

    //空指针异常
    @ExceptionHandler(NullPointerException.class)
    public String nullPointerExceptionHandler(NullPointerException ex) {
        System.err.println("NullPointerException:");
        return resultFormat(2, ex);
    }

    //类型转换异常
    @ExceptionHandler(ClassCastException.class)
    public String classCastExceptionHandler(ClassCastException ex) {
        return resultFormat(3, ex);
    }

    //IO异常
    @ExceptionHandler(IOException.class)
    public String iOExceptionHandler(IOException ex) {
        return resultFormat(4, ex);
    }

    //未知方法异常
    @ExceptionHandler(NoSuchMethodException.class)
    public String noSuchMethodExceptionHandler(NoSuchMethodException ex) {
        return resultFormat(5, ex);
    }

    //数组越界异常
    @ExceptionHandler(IndexOutOfBoundsException.class)
    public String indexOutOfBoundsExceptionHandler(IndexOutOfBoundsException ex) {
        return resultFormat(6, ex);
    }

    //400错误
    @ExceptionHandler({HttpMessageNotReadableException.class})
    public String requestNotReadable(HttpMessageNotReadableException ex) {
        System.out.println("400..requestNotReadable");
        return resultFormat(7, ex);
    }

    //400错误
    @ExceptionHandler({TypeMismatchException.class})
    public String requestTypeMismatch(TypeMismatchException ex) {
        System.out.println("400..TypeMismatchException");
        return resultFormat(8, ex);
    }

    //400错误
    @ExceptionHandler({MissingServletRequestParameterException.class})
    public String requestMissingServletRequest(MissingServletRequestParameterException ex) {
        System.out.println("400..MissingServletRequest");
        return resultFormat(9, ex);
    }

    //405错误
    @ExceptionHandler({HttpRequestMethodNotSupportedException.class})
    public String request405(HttpRequestMethodNotSupportedException ex) {
        return resultFormat(10, ex);
    }

    //406错误
    @ExceptionHandler({HttpMediaTypeNotAcceptableException.class})
    public String request406(HttpMediaTypeNotAcceptableException ex) {
        System.out.println("406...");
        return resultFormat(11, ex);
    }

    //500错误
    @ExceptionHandler({ConversionNotSupportedException.class, HttpMessageNotWritableException.class})
    public String server500(RuntimeException ex) {
        System.out.println("500...");
        return resultFormat(12, ex);
    }

    //栈溢出
    @ExceptionHandler({StackOverflowError.class})
    public String requestStackOverflow(StackOverflowError ex) {
        return resultFormat(13, ex);
    }

    //除数不能为0
    @ExceptionHandler({ArithmeticException.class})
    public String arithmeticException(ArithmeticException ex) {
        return resultFormat(13, ex);
    }


    //其他错误
    @ExceptionHandler({Exception.class})
    public String exception(Exception ex) {
        return resultFormat(14, ex);
    }

    private <T extends Throwable> String resultFormat(Integer code, T ex) {
        ex.printStackTrace();
        log.error(String.format(logExceptionFormat, code, ex.getMessage()));
        return JsonResult.failed(code, ex.getMessage());
    }

}

代码写完了，讲解一下几个新的注解:

@ControllerAdvice: 可以用于定义@ExceptionHandler、@InitBinder、@ModelAttribute，并应用到所有@RequestMapping中

@ExceptionHandler:标识异常类型对应的处理方法

比如下面这个方法:就是处理当遇到了空指针异常对应的处理方法

@ExceptionHandler(NullPointerException.class)

public String nullPointerExceptionHandler(NullPointerException ex) {

    System.err.println("NullPointerException:");

    return resultFormat(2, ex);

}

接下来写一个测试的controller:

package com.springboot.exception.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
/**
* @Author 18011618
* @Date 15:59 2018/7/13
* @Function 测试异常的controller
*/
@RestController
public class ExceptionController {

    @RequestMapping("/exce")
    public String showInfo(){
        System.err.println("dddddddddddddd");
        String info ="你好";
        int a = 1/0;
        return info;
    }
}

最看看一下对应的application.yaml配置文件

server:
  port: 8888

最后写一个启动应用类:

package com.springboot.exception;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

/**
 * @Author 18011618
 * @Description
 * @Date 16:00 2018/7/13
 * @Modify By
 */
@SpringBootApplication
public class ExceptionApplication {
    public static void main(String[] args) {
        SpringApplication.run(ExceptionApplication.class,args);
    }
}

这个时候启动应用类之后，然后访问浏览器 http://localhost:8888/exce 对应的效果如下

这个返回的消息就是全局异常帮忙处理的。其它异常也可以去测试 都是可以拦截的，这里要注意一下:

如果不想用@ResponseBody的话，可以使用@RestControllerAdvice代替@ControllerAdvice

OK 效果实现了,它主要是在Spring mvc 启动时调用RequestMappingHandlerAdapter类的initControllerAdviceCache()方法进行初始化

到此为止，全局异常处理就讲解完了

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