java - org.springframework.web.util.NestedServletException : Request processing failed; nested exception is java. lang.NullPointerException in REST with Spring

Question

我正在尝试使用 Spring 创建 REST 服务。当我尝试访问该服务时，它返回正确的数据但显示 -

Exception handling request to /RESTServ/user/2: org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:982) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:687) [jboss-servlet-api_3.1_spec-1.0.0.Final.jar:1.0.0.Final]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790) [jboss-servlet-api_3.1_spec-1.0.0.Final.jar:1.0.0.Final]
    at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:85) [undertow-servlet-1.0.15.Final.jar:1.0.15.Final]
    at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:61) [undertow-servlet-1.0.15.Final.jar:1.0.15.Final]
    at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36) [undertow-servlet-1.0.15.Final.jar:1.0.15.Final]
    at org.wildfly.extension.undertow.security.SecurityContextAssociationHandler.handleRequest(SecurityContextAssociationHandler.java:78)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:25) [undertow-core-1.0.15.Final.jar:1.0.15.Final]
    at io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:113) [undertow-servlet-1.0.15.Final.jar:1.0.15.Final]
    at io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:56) [undertow-servlet-1.0.15.Final.jar:1.0.15.Final]
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:25) [undertow-core-1.0.15.Final.jar:1.0.15.Final]
    at io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:45) [undertow-core-1.0.15.Final.jar:1.0.15.Final]
    at io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:61) [undertow-servlet-1.0.15.Final.jar:1.0.15.Final]
    at io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:58) [undertow-core-1.0.15.Final.jar:1.0.15.Final]
    at io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:70) [undertow-servlet-1.0.15.Final.jar:1.0.15.Final]
    at io.undertow.security.handlers.SecurityInitialHandler.handleRequest(SecurityInitialHandler.java:76) [undertow-core-1.0.15.Final.jar:1.0.15.Final]
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:25) [undertow-core-1.0.15.Final.jar:1.0.15.Final]
    at org.wildfly.extension.undertow.security.jacc.JACCContextIdHandler.handleRequest(JACCContextIdHandler.java:61)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:25) [undertow-core-1.0.15.Final.jar:1.0.15.Final]
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:25) [undertow-core-1.0.15.Final.jar:1.0.15.Final]
    at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:240) [undertow-servlet-1.0.15.Final.jar:1.0.15.Final]
    at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:227) [undertow-servlet-1.0.15.Final.jar:1.0.15.Final]
    at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:73) [undertow-servlet-1.0.15.Final.jar:1.0.15.Final]
    at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:146) [undertow-servlet-1.0.15.Final.jar:1.0.15.Final]
    at io.undertow.server.Connectors.executeRootHandler(Connectors.java:177) [undertow-core-1.0.15.Final.jar:1.0.15.Final]
    at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:727) [undertow-core-1.0.15.Final.jar:1.0.15.Final]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [rt.jar:1.8.0_45]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [rt.jar:1.8.0_45]
    at java.lang.Thread.run(Thread.java:745) [rt.jar:1.8.0_45]
Caused by: java.lang.NullPointerException
    at java.util.ArrayList.<init>(ArrayList.java:177) [rt.jar:1.8.0_45]
    at io.undertow.servlet.spec.HttpServletResponseImpl.getHeaders(HttpServletResponseImpl.java:248) [undertow-servlet-1.0.15.Final.jar:1.0.15.Final]
    at org.springframework.http.server.ServletServerHttpResponse$ServletResponseHttpHeaders.get(ServletServerHttpResponse.java:160) [spring-web-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.http.server.ServletServerHttpResponse$ServletResponseHttpHeaders.containsKey(ServletServerHttpResponse.java:142) [spring-web-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.addContentDispositionHeader(AbstractMessageConverterMethodProcessor.java:349) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:221) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:153) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:165) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:80) [spring-web-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:126) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:814) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:737) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    ... 30 more

谁能帮我解决这个问题？我已经检查了它返回的数据，通过应用断点它不为空，但它仍然显示上述异常。

编辑:

代码是:
用户.java
包 com.rest.service;

public class User {

    private int userid;
    private String firstName;
    private String lastName;
    private String email;

    public int getUserid() {
        return userid;
    }

    public void setUserid(int userid) {
        this.userid = userid;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    @Override
    public String toString() {
        return "User [userid=" + userid + ", firstName=" + firstName
                + ", lastName=" + lastName + ", email=" + email + "]";
    }

}

SpringServiceController.java

package com.rest.controller;

import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import com.rest.dao.UserService;
import com.rest.service.User;

@RestController
@RequestMapping("/user/")
public class SpringServiceController {

    UserService userService = new UserService();

    @RequestMapping(value = "/{id}", method = RequestMethod.GET, headers = "Accept=application/json")
    public User getUser(@PathVariable int id) {
        User user = userService.getUserById(id);
        return user;
    }
}

我正在使用 UserService.java 从数据库获取数据
DBUtility 是连接到 JDBC 的类

 package com.rest.dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

import com.rest.service.User;
import com.rest.utility.DBUtility;

public class UserService {

    private Connection connection;

    public UserService() {
        connection = DBUtility.getConnection();
    }

    public List<User> getAllUsers() {
        List<User> users = new ArrayList<User>();
        try {
            Statement statement = connection.createStatement();
            ResultSet rs = statement
                    .executeQuery("select * from tblUser");
            while (rs.next()) {
                User user = new User();
                user.setUserid(rs.getInt("userid"));
                user.setFirstName(rs.getString("firstname"));
                user.setLastName(rs.getString("lastname"));
                user.setEmail(rs.getString("email"));
                users.add(user);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }

        return users;
    }

    public User getUserById(int userId) {
        User user = new User();
        try {
            PreparedStatement preparedStatement = connection.prepareStatement("select * from tblUser where userid=?");
            preparedStatement.setInt(1, userId);
            ResultSet rs = preparedStatement.executeQuery();

            if (rs.next()) {
                user.setUserid(rs.getInt("userid"));
                user.setFirstName(rs.getString("firstname"));
                user.setLastName(rs.getString("lastname"));

                user.setEmail(rs.getString("email"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }catch (Exception e) {
            System.out.println("Exception is: "+e);
            e.printStackTrace();
        }
        return user;
    }

}

我的 web.xml 是

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>RESTServ</display-name>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
  <servlet>
    <servlet-name>rest</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>/WEB-INF/rest-servlet.xml</param-value>
        </init-param>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>rest</servlet-name>
    <url-pattern>/*</url-pattern>
  </servlet-mapping>
  <listener>
    <listener-class>
        org.springframework.web.context.ContextLoaderListener
    </listener-class>
</listener>
</web-app>

这是我的 rest-servlet.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:p="http://www.springframework.org/schema/p"
    xsi:schemaLocation=" http://www.springframework.org/schema/beans    
        http://www.springframework.org/schema/beans/spring-beans-4.2.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-4.2.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc-4.2.xsd">
    <context:component-scan base-package="com.rest.controller" />
    <mvc:annotation-driven />
</beans>

PS:当我从 spring xml 文件中删除注释驱动的标签时，还有一件事，然后它适用于简单的数据类型。但它在需要 json 转换的地方不起作用。我正在使用 WildFly - 8.1

Answer 1

这是 WildFly - 8.1 的问题，您必须使用 WildFly - 8.2 或使用 Jboss 7。