《2小时学会Spring Boot》（三）_20181020

• 服务响应对象

ServerResponse 服务响应类

/**
 * 服务响应类
 * Created by gf on 2018/10/20.
 */
//保证序列化json的时候，如果是null的对象，key也会消失
@JsonSerialize(include = JsonSerialize.Inclusion.NON_NULL)
public class ServerResponse implements Serializable{

    private int code;   //状态码
    private String msg; //描述
    private T data;     //对象

    private ServerResponse(int code) {
        this.code = code;
    }

    private ServerResponse(int code, String msg) {
        this.code = code;
        this.msg = msg;
    }

    private ServerResponse(int code, String msg, T data) {
        this.code = code;
        this.msg = msg;
        this.data = data;
    }

    private ServerResponse(int code, T data) {
        this.code = code;
        this.data = data;
    }

    /**
     * 判断这个响应是否是一个成功的响应
     * @return
     */
    @JsonIgnore //使这个方法的返回值不在Json序列化结果当中
    public boolean isSuccess(){
        return this.code==ResponseCode.SUCCESS.getCode();
    }
    public int getCode() {
        return code;
    }

    public String getMsg() {
        return msg;
    }

    public T getData() {
        return data;
    }

    /**
     * 单例模式 创建返回响应对象
     */

    public static  ServerResponse createBySuccess(){
        return new ServerResponse(ResponseCode.SUCCESS.getCode());
    }

    public static  ServerResponse createBySuccessMessage(String msg){
        return new ServerResponse(ResponseCode.SUCCESS.getCode(),msg);
    }

    public static  ServerResponse createBySuccessData(T data){
        return new ServerResponse(ResponseCode.SUCCESS.getCode(),data);
    }

    public static  ServerResponse createBySuccessMsgData(String msg,T data){
        return new ServerResponse(ResponseCode.SUCCESS.getCode(),msg,data);
    }

    public static  ServerResponse createByError(){
        return new ServerResponse(ResponseCode.ERROR.getCode(),ResponseCode.ERROR.getDesc());
    }

    public static  ServerResponse createByErrorMessage(String errorMsg){
        return new ServerResponse(ResponseCode.ERROR.getCode(),errorMsg);
    }

    public static  ServerResponse createByErrorCodeMessage(int errorCode,String errorMsg){
        return new ServerResponse(errorCode,errorMsg);
    }

}

ResponseCode 枚举常量类

/**
 * 枚举常量
 * Created by gf on 2018/10/20.
 */
public enum  ResponseCode {

    SUCCESS(0,"SUCCESS"),
    ERROR(1,"ERROR"),
    NEED_LOGIN(10,"NEED_LOGIN"),
    ILLEGAL_ARGUMENT(20,"ILLEGAL_ARGUMENT");

    private int code;
    private String desc;

    ResponseCode(int code, String desc) {
        this.code = code;
        this.desc = desc;
    }

    public int getCode() {
        return code;
    }

    public String getDesc() {
        return desc;
    }
}

Controller方法中的应用

 /**
     * 添加
     * @return
     */
    @PostMapping(value = "/add")
    public ServerResponse addStudent(@Valid Student student,
                                     BindingResult bindingResult){
        if(bindingResult.hasErrors())
            return ServerResponse.createByErrorMessage(bindingResult.getFieldError().getDefaultMessage());
        return ServerResponse.createBySuccessData(studentRepository.save(student));
    }

• 统一异常处理

自定义异常

应用场景：JDK中的异常类型不能满足程序的需要时，可以自定义异常
实现方式：继承Exception和RunTimeException
Spring framework 针对RuntimeException才会进行事务回滚

public class StudentException extends RuntimeException {

    private int code;

    public StudentException(int code,String exceptionMsg) {
        super(exceptionMsg);
        this.code = code;
    }

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }
}

异常捕获
@ControllerAdvice + @ExceptionHandler 全局处理 Controller 层异常

@ControllerAdvice
标注的类为异常处理类
@ExceptionHandler(value = Exception.class)
标注的当前方法为异常处理方法

@ControllerAdvice //标注的类为异常处理类
public class ExceptionHandle {

    private static Logger logger = LoggerFactory.getLogger(ExceptionHandle.class);

    @ExceptionHandler(value = Exception.class) //标注的当前方法为异常处理方法
    @ResponseBody
    private ServerResponse handle(Exception e){
        if(e instanceof StudentException){
            StudentException se = (StudentException)e;
            return ServerResponse.createByErrorCodeMessage(se.getCode(),se.getMessage());
        }
        logger.info("【异常信息】",e.toString());
        return ServerResponse.createByErrorCodeMessage(ResponseCode.ERROR_EXCEPTION.getCode(),ResponseCode.ERROR_EXCEPTION.getDesc());
    }
}

抛出异常

public ServerResponse> findByAge(Integer age) throws StudentException {
        if(age<10)
            throw  new StudentException(StudentExceptionCode.PRIMARY_SCHOOL);
        else if (age>10&&age<15)
            throw new StudentException(StudentExceptionCode.MIDDLE_SCHOOL);
        return ServerResponse.createBySuccessData(studentRepository.findByAge(age));
    }

项目地址：https://gitee.com/goofyw/spring-boot-demo1/tree/v1.2/