Implementing a Global Exception Handler in Spring Boot

In Spring Boot projects, repetitive try‑catch blocks reduce readability, so a unified global exception handling mechanism is recommended.

First, define a generic AjaxResult class to encapsulate success flag, status code, message and data.

public class AjaxResult {
    //是否成功
    private Boolean success;
    //状态码
    private Integer code;
    //提示信息
    private String msg;
    //数据
    private Object data;
    public AjaxResult() {}
    public AjaxResult(Boolean success, Integer code, String msg, Object data) {
        this.success = success;
        this.code = code;
        this.msg = msg;
        this.data = data;
    }
    public static AjaxResult defineError(BusinessException de) {
        AjaxResult result = new AjaxResult();
        result.setSuccess(false);
        result.setCode(de.getErrorCode());
        result.setMsg(de.getErrorMsg());
        result.setData(null);
        return result;
    }
    public static AjaxResult otherError(ErrorEnum errorEnum) {
        AjaxResult result = new AjaxResult();
        result.setMsg(errorEnum.getErrorMsg());
        result.setCode(errorEnum.getErrorCode());
        result.setSuccess(false);
        result.setData(null);
        return result;
    }
    // getters and setters omitted for brevity
}

Second, create a custom BusinessException extending RuntimeException to carry an error code and message.

public class BusinessException extends RuntimeException {
    private static final long serialVersionUID = 1L;
    protected Integer errorCode;
    protected String errorMsg;
    public BusinessException() {}
    public BusinessException(Integer errorCode, String errorMsg) {
        this.errorCode = errorCode;
        this.errorMsg = errorMsg;
    }
    public Integer getErrorCode() { return errorCode; }
    public void setErrorCode(Integer errorCode) { this.errorCode = errorCode; }
    public String getErrorMsg() { return errorMsg; }
    public void setErrorMsg(String errorMsg) { this.errorMsg = errorMsg; }
}

Third, use an ErrorEnum enumeration to avoid hard‑coded error values.

public enum ErrorEnum {
    SUCCESS(200, "成功"),
    NO_PERMISSION(403, "你没得权限"),
    NO_AUTH(401, "未登录"),
    NOT_FOUND(404, "未找到该资源!"),
    INTERNAL_SERVER_ERROR(500, "服务器异常请联系管理员");
    private Integer errorCode;
    private String errorMsg;
    ErrorEnum(Integer errorCode, String errorMsg) {
        this.errorCode = errorCode;
        this.errorMsg = errorMsg;
    }
    public Integer getErrorCode() { return errorCode; }
    public String getErrorMsg() { return errorMsg; }
}

Finally, implement a @RestControllerAdvice class GlobalExceptionHandler that catches BusinessException and generic Exception , logs the error, and returns an appropriate AjaxResult .

@RestControllerAdvice
public class GlobalExceptionHandler {
    private static final Logger log = LoggerFactory.getLogger(GlobalExceptionHandler.class);
    @ExceptionHandler(BusinessException.class)
    public AjaxResult bizExceptionHandler(BusinessException e) {
        log.error(e.getMessage(), e);
        return AjaxResult.defineError(e);
    }
    @ExceptionHandler(Exception.class)
    public AjaxResult exceptionHandler(Exception e) {
        log.error(e.getMessage(), e);
        return AjaxResult.otherError(ErrorEnum.INTERNAL_SERVER_ERROR);
    }
}

Integrating these components requires only simple configuration and can be extended for finer‑grained business exceptions, greatly improving code cleanliness and maintainability.