Spring JPA使用方法existsByUserName（字符串用户名）时出现提示性错误；

我已经创建了一个

JpaRepository

接口，在这里我定义了一个名为

existsByUserName（字符串用户名）

的方法。但是由于这个方法，我得到了错误

UserRepository

界面

package org.avijit.DAO; import org.avijit.Domain.User; 
import org.springframework.data.jpa.repository.JpaRepository; 
import org.springframework.stereotype.Repository;

@Repository
public interface UserRepository extends JpaRepository<User, Integer> {

            boolean existsByUserName(String userName);
}

我的

实体

类是

package org.avijit.Controller;


import org.avijit.DAO.UserRepository;
import org.avijit.Domain.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import javax.validation.Valid;
import java.util.List;

@Controller
public class baseController {

    @Autowired
    UserRepository userRepository;

    @RequestMapping("/")
    public String homePage() {
        System.out.println(userRepository.findAll());
        return "HomePage";
    }

    @RequestMapping("/register")
    public String register(Model model) {
        model.addAttribute(new User());
        return "RegistrationPage";
    }

    @RequestMapping(value = "/doRegistration", method = RequestMethod.POST)
    public String doRegistration(@Valid @ModelAttribute("user") User user, BindingResult result) {
        if (result.hasErrors()) {
            return "RegistrationPage";
        } else {
            if (user.getId() < 0) {
                userRepository.save(user);
                return "redirect:/memberList";
            } else {
                User tempUser = userRepository.findOne(user.getId());
                if (!tempUser.getUserName().equals(user.getUserName()) && userRepository.existsByUserName(user.getUserName())) {
                    result.rejectValue("userName", "DuplicateKey.user.userName", "This username already exist! Try again !");
                    return "RegistrationPage";
                } else {
                    tempUser.setFirstName(user.getFirstName());
                    tempUser.setLastName(user.getLastName());
                    tempUser.setUserName(user.getUserName());
                    tempUser.setMobile(user.getMobile());
                    tempUser.setAddress(user.getAddress());
                    tempUser.setPassword(user.getPassword());
                    userRepository.save(tempUser);
                    return "redirect:/memberList";
                }

            }
        }
    }


    @RequestMapping(value = "/memberList")

    public String memberList(Model model) {
        List<User> list = userRepository.findAll();
        model.addAttribute("list", list);
        return "UserList";
    }

}

package org.avijit.Domain;

import org.hibernate.validator.constraints.NotBlank;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

@Entity
public class User {

    @Id
    @GeneratedValue
    private Integer id;
    @NotBlank
    private String firstName;
    @NotBlank
    private String lastName;
    @NotBlank
    private String userName;
    @NotBlank
    private String mobile;
    @NotBlank
    private String address;
    @NotBlank
    private String password;

    public User() {

    }

    public User(String firstName, String lastName, String userName, String mobile, String address, String password) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.userName = userName;
        this.mobile = mobile;
        this.address = address;
        this.password = password;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    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 getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getMobile() {
        return mobile;
    }

    public void setMobile(String mobile) {
        this.mobile = mobile;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", firstName='" + firstName + '\'' +
                ", lastName='" + lastName + '\'' +
                ", userName='" + userName + '\'' +
                ", mobile='" + mobile + '\'' +
                ", address='" + address + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

我的

pom.xml

是

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xmlns="http://maven.apache.org/POM/4.0.0"
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<groupId>org.avijit.jpaproject</groupId>
<artifactId>jpaproject</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>war</packaging>

<dependencies>

    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-webmvc</artifactId>
        <version>4.3.4.RELEASE</version>
    </dependency>

    <dependency>
        <groupId>org.springframework.data</groupId>
        <artifactId>spring-data-jpa</artifactId>
        <version>1.9.2.RELEASE</version>
    </dependency>

    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>4.3.4.RELEASE</version>
    </dependency>

    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-orm</artifactId>
        <version>4.3.4.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context-support</artifactId>
        <version>4.3.4.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-expression</artifactId>
        <version>4.3.4.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-tx</artifactId>
        <version>4.3.4.RELEASE</version>
    </dependency>

    <dependency>
        <groupId>org.springframework.security</groupId>
        <artifactId>spring-security-taglibs</artifactId>
        <version>4.2.4.RELEASE</version>
    </dependency>

    <dependency>
        <groupId>org.springframework.security</groupId>
        <artifactId>spring-security-web</artifactId>
        <version>4.2.4.RELEASE</version>
    </dependency>

    <dependency>
        <groupId>org.springframework.security</groupId>
        <artifactId>spring-security-config</artifactId>
        <version>4.2.4.RELEASE</version>
    </dependency>


    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>4.3.11.Final</version>
    </dependency>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-entitymanager</artifactId>
        <version>4.3.11.Final</version>
    </dependency>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-validator</artifactId>
        <version>5.3.4.Final</version>
    </dependency>


    <!--Extra Dependency -->

    <dependency>
        <groupId>jstl</groupId>
        <artifactId>jstl</artifactId>
        <version>1.2</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.41</version>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>3.1.0</version>
    </dependency>
    <dependency>
        <groupId>commons-dbcp</groupId>
        <artifactId>commons-dbcp</artifactId>
        <version>1.4</version>
    </dependency>
    <dependency>
        <groupId>javax.validation</groupId>
        <artifactId>validation-api</artifactId>
        <version>2.0.1.Final</version>
    </dependency>
    <dependency>
        <groupId>javax.inject</groupId>
        <artifactId>javax.inject</artifactId>
        <version>1</version>
    </dependency>
</dependencies>

4.0.0
org.avijit.jpa项目
JPA项目
1.0-快照
战争
org.springframework
SpringWebMVC
4.3.4.1发布
org.springframework.data
spring数据jpa
1.9.2.1发布
org.springframework
弹簧芯
4.3.4.1发布
org.springframework
春季甲虫
4.3.4.1发布
org.springframework
spring上下文支持
4.3.4.1发布
org.springframework
弹簧式
4.3.4.1发布
org.springframework
德克萨斯州春季
4.3.4.1发布
org.springframework.security
spring安全标记库
4.2.4.1发布
org.springframework.security
spring安全网
4.2.4.1发布
org.springframework.security
spring安全配置
4.2.4.1发布
org.hibernate
冬眠核心
4.3.11.4最终版本
org.hibernate
休眠实体管理器
4.3.11.4最终版本
org.hibernate
休眠验证器
5.3.4.最终版本
jstl
jstl
1.2
mysql
mysql连接器java
5.1.41
javax.servlet
javax.servlet-api
3.1.0
公共dbcp
公共dbcp
1.4
javax.validation
验证api
2.0.1.最终版本
javax.inject
javax.inject
1.

下面是错误堆栈跟踪

 org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'baseController': Unsatisfied dependency expressed through field 'userRepository'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userRepository': Invocation of init method failed; nested exception is org.springframework.data.mapping.PropertyReferenceException: No property existsByUserName found for type User!
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:592)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:370)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1219)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:551)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:754)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:866)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:542)
    at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:444)
    at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:326)
    at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:107)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4727)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5189)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:752)
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:728)
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:734)
    at org.apache.catalina.startup.HostConfig.manageApp(HostConfig.java:1702)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:300)
    at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
    at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
    at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:482)
    at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:431)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:300)
    at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
    at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
    at javax.management.remote.rmi.RMIConnectionImpl.doOperation(RMIConnectionImpl.java:1468)
    at javax.management.remote.rmi.RMIConnectionImpl.access$300(RMIConnectionImpl.java:76)
    at javax.management.remote.rmi.RMIConnectionImpl$PrivilegedOperation.run(RMIConnectionImpl.java:1309)
    at javax.management.remote.rmi.RMIConnectionImpl.doPrivilegedOperation(RMIConnectionImpl.java:1401)
    at javax.management.remote.rmi.RMIConnectionImpl.invoke(RMIConnectionImpl.java:829)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:361)
    at sun.rmi.transport.Transport$1.run(Transport.java:200)
    at sun.rmi.transport.Transport$1.run(Transport.java:197)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.Transport.serviceCall(Transport.java:196)
    at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:568)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:826)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$0(TCPTransport.java:683)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:682)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userRepository': Invocation of init method failed; nested exception is org.springframework.data.mapping.PropertyReferenceException: No property existsByUserName found for type User!
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1583)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:553)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
    at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:207)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1131)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1059)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:589)
    ... 60 more
Caused by: org.springframework.data.mapping.PropertyReferenceException: No property existsByUserName found for type User!
    at org.springframework.data.mapping.PropertyPath.<init>(PropertyPath.java:75)
    at org.springframework.data.mapping.PropertyPath.create(PropertyPath.java:327)
    at org.springframework.data.mapping.PropertyPath.create(PropertyPath.java:307)
    at org.springframework.data.mapping.PropertyPath.from(PropertyPath.java:270)
    at org.springframework.data.mapping.PropertyPath.from(PropertyPath.java:241)
    at org.springframework.data.repository.query.parser.Part.<init>(Part.java:76)
    at org.springframework.data.repository.query.parser.PartTree$OrPart.<init>(PartTree.java:235)
    at org.springframework.data.repository.query.parser.PartTree$Predicate.buildTree(PartTree.java:373)
    at org.springframework.data.repository.query.parser.PartTree$Predicate.<init>(PartTree.java:353)
    at org.springframework.data.repository.query.parser.PartTree.<init>(PartTree.java:84)
    at org.springframework.data.jpa.repository.query.PartTreeJpaQuery.<init>(PartTreeJpaQuery.java:61)
    at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$CreateQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:95)
    at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$CreateIfNotFoundQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:206)
    at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$AbstractQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:73)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.<init>(RepositoryFactorySupport.java:367)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport.getRepository(RepositoryFactorySupport.java:190)
    at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.initAndReturn(RepositoryFactoryBeanSupport.java:239)
    at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.afterPropertiesSet(RepositoryFactoryBeanSupport.java:225)
    at org.springframework.data.jpa.repository.support.JpaRepositoryFactoryBean.afterPropertiesSet(JpaRepositoryFactoryBean.java:92)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1642)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1579)

org.springframework.beans.factory.UnsatifiedDependencyException:创建名为“baseController”的bean时出错：通过字段“userRepository”表示未满足的依赖关系；嵌套异常为org.springframework.beans.factory.BeanCreationException:创建名为“userRepository”的bean时出错：调用init方法失败；嵌套异常为org.springframework.data.mapping.PropertyReferenceException:找不到类型User的属性existsByUserName！
位于org.springframework.beans.factory.annotation.AutoWiredNotationBeanPostProcessor$AutoWiredFeldElement.inject（AutoWiredNotationBeanPostProcessor.java:592）
位于org.springframework.beans.factory.annotation.InjectionMetadata.inject（InjectionMetadata.java:88）
位于org.springframework.beans.factory.annotation.AutoWiredNotationBeanPostProcessor.postProcessPropertyValues（AutoWiredNotationBeanPostProcessor.java:370）
位于org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean（AbstractAutowireCapableBeanFactory.java:1219）
位于org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean（AbstractAutowireCapableBeanFactory.java:551）
位于org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean（AbstractAutowireCapableBeanFactory.java:482）
位于org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject（AbstractBeanFactory.java:306）
位于org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton（DefaultSingletonBeanRegistry.java:230）
位于org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean（AbstractBeanFactory.java:302）
位于org.springframework.beans.factory.support.AbstractBeanFactory.getBean（AbstractBeanFactory.java:197）
位于org.springframework.beans.factory.support.DefaultListableBeanFactory.PreInstanceSingleton（DefaultListableBeanFactory.java:754）
位于org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization（AbstractApplicationContext.java:866）
位于org.springframework.context.support.AbstractApplicationContext.refresh（AbstractApplicationContext.java:542）
位于org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext（ContextLoader.java:444）
位于org.springframework.web.context.ContextLoader.initWebApplicationContext（ContextLoader.java:326）
位于org.springframework.web.context.ContextLoaderListener.contextInitialized（ContextLoaderListener.java:107）
位于org.apache.catalina.core.StandardContext.listenerStart（StandardContext.java:4727）
位于org.apache.catalina.core.StandardContext.startInternal（StandardContext.java:5189）
位于org.apache.catalina.util.LifecycleBase.start（LifecycleBase.java:150）
位于org.apache.catalina.core.ContainerBase.addChildInternal（ContainerBase.java:752）
位于org.apache.catalina.core.ContainerBase.addChild（ContainerBase.java:728）
位于org.apache.catalina.core.StandardHost.addChild（StandardHost.java:734）
位于org.apache.catalina.startup.HostConfig.manageApp（HostConfig.java:1702）
在sun.reflect.NativeMethodAccessorImpl.invoke0（本机方法）处
位于sun.reflect.NativeMethodAccessorImpl.invoke（NativeMethodAccessorImpl.java:62）
在sun.reflect.DelegatingMethodAccessorImpl.invoke（DelegatingMethodAccessorImpl.java:43）中
位于java.lang.reflect.Method.invoke（Method.java:498）
位于org.apache.tomcat.util.modeler.BaseModelMBean.invoke（BaseModelMBean.java:300）
位于com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke（DefaultMBeanServerInterceptor.java:819）
位于com.sun.jmx.mbeanserver.JmxMBeanServer.invoke（JmxMBeanServer.java:801）
位于org.apache.catalina.mbeans.MBeanFactory.createStandardContext（MBeanFactory.java:482）
位于org.apache.catalina.mbeans.MBeanFactory.createStandardContext（MBeanFactory.java:431）
在sun.reflect.NativeMethodAccessorImpl.invoke0（本机方法）处
在sun.reflect.NativeMethodAccessorImpl.invoke（NativeMethod
@Query("SELECT CASE WHEN COUNT(u) > 0 THEN 'true' ELSE 'false' END FROM ENTITY e WHERE e.username = :userName")

@Repository public interface UserRepository extends JpaRepository {

@Repository public interface UserRepository extends JpaRepository<User,<data_type_primary_key>> {

<dependency>
            <groupId>org.springframework.data</groupId>
            <artifactId>spring-data-jpa</artifactId>
            <version>1.11.9.RELEASE</version>
        </dependency>