java spring BeanCreationException 关于映射的混淆

spring BeanCreationException confusion about mapping

提问by markjason72

trying to integrate hibernate and spring ,I ran into this error

试图集成休眠和弹簧，我遇到了这个错误

SEVERE: Context initialization failed org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping': Initialization of bean failed; nested exception is java.lang.IllegalStateException: Cannot map handler 'org.me.spring.hib.school.web.SchoolController#0' to URL path [/allschools]: There is already handler of type [class org.me.spring.hib.school.web.SchoolController] mapped.

严重：上下文初始化失败 org.springframework.beans.factory.BeanCreationException：创建名为“ org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping”的bean 时出错：bean 初始化失败；嵌套异常是java.lang.IllegalStateException：无法将处理程序“ org.me.spring.hib.school.web.SchoolController#0”映射到 URL 路径 [ /allschools]：已org.me.spring.hib.school.web.SchoolController映射类型为 [类] 的处理程序。

My Controller looks like

我的控制器看起来像

package org.me.spring.hib.school.web;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.me.spring.hib.school.dao.SchoolDAO;
import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;

@Controller
public class SchoolController {
    private SchoolDAO schoolDao;

    public SchoolDAO getSchoolDao() {
        return schoolDao;
    }

    public void setSchoolDao(SchoolDAO schoolDao) {
        this.schoolDao = schoolDao;
    }
        @RequestMapping("/allschools")
    public ModelAndView showAllSchools(HttpServletRequest request,HttpServletResponse response) throws Exception{
        if(this.schoolDao ==null){
            System.out.println("this.schoolDao is null");
        }
        ModelMap modelMap = new ModelMap();
        modelMap.addAttribute("schoolsList", this.schoolDao.getAllSchools());
        return new ModelAndView("allschools", modelMap);
    }

}

I have injected the dao implementation in app context file

我已经在应用上下文文件中注入了 dao 实现

    <context:component-scan base-package="org.me.spring.hib.school.web" />

    <bean id="hibernateTemplate" class="org.springframework.orm.hibernate3.HibernateTemplate"> 
       <property name="sessionFactory" >
           <ref bean="sessionFactory" />
       </property>    
    </bean>

    <bean id="sessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
       <property name="dataSource">
          <ref local="dataSource"/>
       </property>
       <property name="annotatedClasses">
            <list>
                <value>org.me.spring.hib.school.domain.School</value>
                <value>org.me.spring.hib.school.domain.Teacher</value>
                <value>org.me.spring.hib.school.domain.Student</value>
            </list>
       </property>


       <property name="hibernateProperties">
        <props>
                <prop key="hibernate.dialect"> org.hibernate.dialect.HSQLDialect</prop>
                <prop key="hibernate.show_sql">true</prop>
                <prop key="hibernate.hbm2ddl.auto">create</prop>
        </props>
       </property>

   </bean>

    <bean id="schoolDao" class="org.me.spring.hib.school.dao.SchoolDAOImpl">
        <property name="hibernateTemplate" ref="hibernateTemplate" />
    </bean>


    <bean  class="org.me.spring.hib.school.web.SchoolController" >
            <property name="schoolDao" ref="schoolDao" />
    </bean>

I cannot make out why SchoolController#0is being mapped to the url.

我无法弄清楚为什么 SchoolController#0被映射到 url。

回答by skaffman

This is happening because you have both

发生这种情况是因为您同时拥有

<context:component-scan base-package="org.me.spring.hib.school.web" />

and

和

<bean  class="org.me.spring.hib.school.web.SchoolController" >

The first line will auto-discover and register a SchoolControllerfor you. By explicitly declaring another one, you get a duplicate, and the url-mapping will clash.

第一行将自动发现并SchoolController为您注册。通过显式声明另一个，您会得到一个副本，并且 url 映射将发生冲突。

You need to either remove the <context:component-scan>, or remove the explicit bean definitions for the controller and the DAO. If you do the latter, then you'll need to use autowiring to inject their dependencies.

您需要删除<context:component-scan>，或者删除控制器和 DAO 的显式 bean 定义。如果你做后者，那么你需要使用自动装配来注入它们的依赖项。

回答by Sanjeevan

I faced similar kind of problem. I have defined the controller class with "@Controller" and also in the Spring-config.xml file as a bean and have injected the dependencies.

我遇到了类似的问题。我已经用“@Controller”定义了控制器类，也在 Spring-config.xml 文件中定义了一个 bean 并注入了依赖项。

This was causing the problem. @Controller is defining the bean and again, the bean defined in the xml file is redefining the dependencies. I tried autowiring the dependency and removed it as a bean from the xml file. Then it worked.

这导致了问题。@Controller 正在定义 bean，同样，xml 文件中定义的 bean 正在重新定义依赖项。我尝试自动装配依赖项并将其作为 bean 从 xml 文件中删除。然后它起作用了。

回答by Jaikrat

Or you can mention <mvc:annotation-driven/>in your XML and remove the

或者您可以<mvc:annotation-driven/>在 XML 中提及并删除

<context:component-scan base-package="org.me.spring.hib.school.web" />part.

<context:component-scan base-package="org.me.spring.hib.school.web" />部分。

If you are comfortable with XML notations.

如果您对 XML 表示法感到满意。