1.定义全局算术异常处理器，返回格式为：{"msg":"算术异常","code":-1} * 2.定义全局空指针异常处理器，返回格式为：{"msg":"空指针异常","code":-2}

在Spring MVC中，你可以通过创建一个带有`@ControllerAdvice`注解的类，并在里面定义两个`@ExceptionHandler`方法来实现全局异常处理器。这里是一个例子：

import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;

@ControllerAdvice
public class GlobalExceptionHandler {

    @ExceptionHandler(ArithmeticException.class)
    public ResponseEntity<ErrorResponse> handleArithmeticException(ArithmeticException e) {
        ErrorResponse response = new ErrorResponse();
        response.setMsg("算术异常");
        response.setCode(-1);
        return ResponseEntity.badRequest().body(response);
    }

    @ExceptionHandler(NullPointerException.class)
    public ResponseEntity<ErrorResponse> handleNullPointerException(NullPointerException e) {
        ErrorResponse response = new ErrorResponse();
        response.setMsg("空指针异常");
        response.setCode(-2);
        return ResponseEntity.serverError().body(response);
    }

    private static class ErrorResponse {
        private String msg;
        private int code;

        // getters and setters...
    }