前置说明

多余的try catch 很影响项目美观，但是异常又不能不处理，这篇主要讲一下如何在springboot项目中统一处理异常。
此篇因为需要在错误时返回json数据，故引用了Java项目构建基础之统一响应篇的统一响应。

必要jar包

<dependencies>
    <!-- spring web -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
	 <!-- lombok 简化代码 -->
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>
</dependencies>

创建自定义异常

@EqualsAndHashCode(callSuper = true)
@Data
@AllArgsConstructor
public class ArgumentException extends RuntimeException {
    // 这里是统一响应中的状态码与信息
    private IResultCode resultCode;
    public ArgumentException(IResultCode resultCode,String message){
        super(resultCode.getMessage()+message);
        this.resultCode = resultCode;
    }
}

验证工具类（类似Asserts）

public class ArgumentUtils {
    /**
     * 验证参数非null
     * <br/>
     * @param o 需要验证的变量
     * @param resultCode 如果为null时希望接口返回什么
     * @author KThirty
     * @since 2020/5/22
     */
    public static void notNull(@Nullable Object o, IResultCode resultCode,String message){
        if(null == o){
            throw new ArgumentException(resultCode,message);
        }
    }
}

异常统一处理

@RestControllerAdvice
@ResponseBody
public class GlobalExceptionHandler {

    /**
     * 父类异常处理
     */
    @ExceptionHandler(Exception.class)
    public R handleException(Exception e){
        return R.fail(ResultCode.FAILURE);
    }

    /**
     * 参数异常
     */
    @ExceptionHandler(ArgumentException.class)
    public R handleArgumentException(ArgumentException e){
        return R.fail(e.getResultCode(),e.getMessage());
    }
    
    /**
     * 空指针异常
     */
    @ExceptionHandler(NullPointerException.class)
    public R handleNullPointerException(NullPointerException e){
        return R.fail(ResultCode.FAILURE,"空指针异常");
    }
}

测试请求

源码

@RestController
@RequestMapping("/test/param")
public class TestParamController {
    @GetMapping("not-null")
    public R testParamNotNull(String name){
        ArgumentUtils.notNull(name, ResultCode.PARAM_MISS,"name 不可为空");
        return R.success();
    }
    @GetMapping("null-point")
    public R testNullPoint(Integer age){
        int i = age.intValue();
        return R.success();
    }
}

步骤

请求http://localhost:8080/test/param/not-null 返回{"code":400,"success":false,"data":null,"message":"缺少必要的请求参数name 不可为空"}
请求http://localhost:8080/test/param/not-null?name=test返回{"code":200,"success":true,"data":null,"message":"操作成功"}
请求http://localhost:8080/test/param/null-point 返回{"code":400,"success":false,"data":null,"message":"空指针异常"}
请求http://localhost:8080/test/param/null-point?age=1返回{"code":200,"success":true,"data":null,"message":"操作成功"}