java - 使用 @Repository、@Service 和 @Controller 注释给出 bean 创建异常？

Question

我创建了一个简单的spring mvc项目来使用STS测试spring中的@Repository、@Service和@Controller注释。但我收到了 BeanCreationException。Spring无法创建@Controller bean，因为它找不到带有@Service注释的bean。由于我使用了STS，所以大部分文件都是自动创建的。我正在共享文件，请告诉我应该进行哪些更改才能解决此问题。

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

    <!-- The definition of the Root Spring Container shared by all Servlets and Filters -->
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/spring/root-context.xml</param-value>
    </context-param>

    <!-- Creates the Spring Container shared by all Servlets and Filters -->
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

    <!-- Processes application requests -->
    <servlet>
        <servlet-name>appServlet</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>/WEB-INF/spring/appServlet/servlet-context.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>appServlet</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

</web-app>

servlet-context.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans:beans xmlns="http://www.springframework.org/schema/mvc"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:beans="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">

    <!-- DispatcherServlet Context: defines this servlet's request-processing infrastructure -->

    <!-- Enables the Spring MVC @Controller programming model -->
    <annotation-driven />

    <!-- Handles HTTP GET requests for /resources/** by efficiently serving up static resources in the ${webappRoot}/resources directory -->
    <resources mapping="/resources/**" location="/resources/" />

    <!-- Resolves views selected for rendering by @Controllers to .jsp resources in the /WEB-INF/views directory -->
    <beans:bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <beans:property name="prefix" value="/WEB-INF/views/" />
        <beans:property name="suffix" value=".jsp" />
    </beans:bean>

    <context:component-scan base-package="com.example.annoproject.Controllers" />
    <context:component-scan base-package="com.example.annoproject.Service" />
    <context:component-scan base-package="com.example.annoproject.dao" />

</beans:beans>

root-context.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <!-- Root Context: defines shared resources visible to all other web components -->

    <bean id="dataSource"
        class="org.springframework.jdbc.datasource.DriverManagerDataSource">

        <property name="driverClassName" value="com.mysql.jdbc.Driver" />
        <property name="url" value="jdbc:mysql://localhost:3306/example_db" />
        <property name="username" value="root" />
        <property name="password" value="password" />
    </bean>

    <bean id = "jdbcTemplate" class = "org.springframework.jdbc.core.JdbcTemplate">
        <constructor-arg ref = "dataSource"/>
    </bean>

    <bean id= "abstractService" class = "com.example.annoproject.service.AbstractService">
    </bean> 

</beans>

用户 Controller

package com.example.annoproject.Controllers;

import com.example.annoproject.dao.UserDAOImpl;
import com.example.annoproject.model.User;
import com.example.annoproject.service.UserService;

@Controller
public class UserController {

    @Autowired
    UserService userService;

    @RequestMapping(value = "/home", method = RequestMethod.GET)
    public String signupPage(Model model){

        userService.getUser("1");
        return "home";
    }
}

UserService.java

package com.example.annoproject.service;

import com.example.annoproject.dao.UserDAO;
import com.example.annoproject.model.User;

@Service("userService")
public class UserService {

    @Autowired
    UserDAO userDao;

    public User getUser(String uid){
        return userDao.getUser(uid);
    }

}

UserDAOImpl.java

package com.example.annoproject.dao;

import com.example.annoproject.model.User;

@Repository("userDao")
public class UserDAOImpl implements UserDAO{

    @Autowired
    JdbcTemplate jdbcTemplate;

    public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
        this.jdbcTemplate = jdbcTemplate;
    }

    @Override
    public User getUser(String id) {

        String query = "SELECT * FROM empl where uid = ? ";

        User user = jdbcTemplate.queryForObject(query, new Object[]{id}, new RowMapper<User>(){

            @Override
            public User mapRow(ResultSet rs, int rowNum) throws SQLException {
                User user = new User();
                user.setFirstName(rs.getString("empF"));
                user.setLastName(rs.getString("emplL"));
                return user;
            }});

        return user;
    }


}

我已经尝试了很多事情。问题是在使用 @Controller UserController 时，尚未创建 userService bean。因此我们得到了异常(exception)。解决方案是在 root-context.xml 中定义 userService bean。但重点是我不想定义任何bean，上下文<context:component-scan..应该照顾好这一点。由于 root-context 是第一个读取的文件(如 web.xml - 部署描述符中所定义)，因此我们需要更改其中的某些内容，以便首先扫描包，并提前创建 userDao、userService、datasource 等 bean。但我无法巧妙地解决它。谁能告诉我标准做法是什么？我在这里缺少什么。谢谢。

顺便说一句，这是完全异常(exception):

WARN : org.springframework.web.context.support.XmlWebApplicationContext - Exception encountered during context initialization - cancelling refresh attempt
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userController': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: com.example.annoproject.service.UserService com.example.annoproject.Controllers.UserController.userService; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.example.annoproject.service.UserService] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:298)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1148)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:458)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:293)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:290)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:191)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:636)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:934)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479)
    at org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:651)
    at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:602)
    at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:665)
    at org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:521)
    at org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:462)
    at org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:136)
    at javax.servlet.GenericServlet.init(GenericServlet.java:158)
    at org.apache.catalina.core.StandardWrapper.initServlet(StandardWrapper.java:1241)
    at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1154)
    at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:1041)
    at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:4944)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5230)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:725)
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:701)
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:714)
    at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:581)
    at org.apache.catalina.startup.HostConfig$DeployDescriptor.run(HostConfig.java:1683)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
    at java.util.concurrent.FutureTask.run(FutureTask.java:262)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:744)

Answer 1

您的上下文扫描包com.example.annoproject.Service。但您的服务位于 com.example.annoproject.service 包中。

尊重命名约定:包仅使用小写。你不会再犯这样的错误了。