关于#Java代码报错的问题，如何解决？(语言-java)

Question

无法通过前台向后台发送请求获取随机验证，但前台却又自动填入了一个随机数，点击登录后报500，报错内容是：

java.lang.NullPointerException: Cannot invoke "Object.toString()" because the return value of "java.util.Map.get(Object)" is null
    at com.itheima.reggie.controller.UserController.login(UserController.java:69) ~[classes/:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:568) ~[na:na]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205) ~[spring-web-5.3.27.jar:5.3.27]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:150) ~[spring-web-5.3.27.jar:5.3.27]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117) ~[spring-webmvc-5.3.27.jar:5.3.27]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) ~[spring-webmvc-5.3.27.jar:5.3.27]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.27.jar:5.3.27]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.27.jar:5.3.27]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1072) ~[spring-webmvc-5.3.27.jar:5.3.27]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:965) ~[spring-webmvc-5.3.27.jar:5.3.27]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.27.jar:5.3.27]
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909) ~[spring-webmvc-5.3.27.jar:5.3.27]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:555) ~[tomcat-embed-core-9.0.75.jar:4.0.FR]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.27.jar:5.3.27]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:623) ~[tomcat-embed-core-9.0.75.jar:4.0.FR]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:209) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) ~[tomcat-embed-websocket-9.0.75.jar:9.0.75]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at com.itheima.reggie.filter.LoginCheckFilter.doFilter(LoginCheckFilter.java:51) ~[classes/:na]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.27.jar:5.3.27]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.27.jar:5.3.27]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:167) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.apache.catalina.core.StandardContextValve.__invoke(StandardContextValve.java:90) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:41002) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:481) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:130) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:390) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:926) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1791) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.75.jar:9.0.75]
    at java.base/java.lang.Thread.run(Thread.java:833) ~[na:na]

Controller代码是：

import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.itheima.reggie.common.R;
import com.itheima.reggie.entity.User;
import com.itheima.reggie.service.UserService;
import com.itheima.reggie.utils.ValidateCodeUtils;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.servlet.http.HttpSession;
import java.util.Map;


@RestController
@RequestMapping("/user")
@Slf4j
public class UserController {

    @Autowired
    private UserService userService;

    /**
     * 发送手机短信验证码
     * @param user
     * @return
     */
    @PostMapping("/sendMsg")
    public R<String> sendMsg(@RequestBody User user, HttpSession session){
        //获取手机号
        String phone = user.getPhone();

        if(StringUtils.isNotEmpty(phone)){
            //生成随机的4位验证码
            String code = ValidateCodeUtils.generateValidateCode(4).toString();
            log.info("code={}",code);

            //调用阿里云提供的短信服务API完成发送短信
            //SMSUtils.sendMessage("瑞吉外卖","",phone,code);

            //需要将生成的验证码保存到Session
            session.setAttribute(phone,code);

            return R.success("手机验证码短信发送成功");
        }

        return R.error("短信发送失败");
    }

    /**
     * 移动端用户登录
     * @param map
     * @param session
     * @return
     */
    @PostMapping("/login")
    public R<User> login(@RequestBody Map map, HttpSession session){
        log.info(map.toString());

        //获取手机号
        String phone = map.get("phone").toString();

        //获取验证码
        String code = map.get("code").toString();

        //从Session中获取保存的验证码
        Object codeInSession = session.getAttribute(phone);

        //进行验证码的比对（页面提交的验证码和Session中保存的验证码比对）
        if(codeInSession != null && codeInSession.equals(code)){
            //如果能够比对成功，说明登录成功

            LambdaQueryWrapper<User> queryWrapper = new LambdaQueryWrapper<>();
            queryWrapper.eq(User::getPhone,phone);

            User user = userService.getOne(queryWrapper);
            if(user == null){
                //判断当前手机号对应的用户是否为新用户，如果是新用户就自动完成注册
                user = new User();
                user.setPhone(phone);
                user.setStatus(1);
                userService.save(user);
            }
            session.setAttribute("user",user.getId());
            return R.success(user);
        }
        return R.error("登录失败");
    }
}

Answer 1

RequestBody 把map换成实体对象