当我提交表单时，Spring 仅在启动时注入我的课程，我的变量为空，为什么？答案

【问题标题】：Spring inject my class only on my startup when I submit my form my variable is null why?当我提交表单时，Spring 仅在启动时注入我的课程，我的变量为空，为什么？
【发布时间】：2014-09-26 17:17:36
【问题描述】：

大家好，我有一个问题，我已经花了几天时间，到目前为止我无法解决我的问题。我正在尝试使用 spring 注入，它在我的启动项目中运行良好，但是当我提交表单时，我的类为空。

按照我的代码：

applicationContext 我有这个：

<context:annotation-config />
<context:component-scan base-package="br.com.allinone"/>
<tx:annotation-driven />

web.xml

<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

和我的班级

@Component
@ManagedBean
@URLMapping(id = "homeAdmin", pattern = "/Home", viewId = "/home.jsf")  
public class HomeBean {

@Autowired
UserService service;
}

@Service
public class UserServiceImpl implements UserService

更多细节：

我的豆子是这样的：

package br.com.allinone.bean;

@Component
@ManagedBean
@URLMapping(id = "homeAdmin", pattern = "/Home", viewId = "/home.jsf")  
public class HomeBean {

    @Autowired
    UserService service;

   @PostConstruct
   public void init(){

    System.out.println( service.getTest() );

  }
    get and set...  

}

我的服务接口是这样的

package br.com.allinone.service;

public interface UserService extends BaseService<TestEntity, Long>{
    public String getTest();
}

我实现的服务类：

package br.com.allinone.service.impl;
@Service
public class UserServiceImpl implements UserService {

public String getTest(){
    return "test";
}

我的 web.xml

<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">
<filter>
    <filter-name>Pretty Filter</filter-name>
    <filter-class>com.ocpsoft.pretty.PrettyFilter</filter-class>
</filter>

 <listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

<context-param>
    <param-name>com.ocpsoft.pretty.DEVELOPMENT</param-name>
    <param-value>true</param-value>
</context-param>
<servlet>
    <servlet-name>Faces Servlet</servlet-name>
    <servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
    <servlet-name>Faces Servlet</servlet-name>
    <url-pattern>*.jsf</url-pattern>
</servlet-mapping>
<servlet-mapping>
    <servlet-name>Faces Servlet</servlet-name>
    <url-pattern>*.xhtml</url-pattern>
</servlet-mapping>
<filter-mapping>
    <filter-name>Pretty Filter</filter-name>
    <url-pattern>/*</url-pattern>
    <dispatcher>FORWARD</dispatcher>
    <dispatcher>REQUEST</dispatcher>
    <dispatcher>ERROR</dispatcher>
    </filter-mapping>
</web-app>

还有我的 applicationContext.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:util="http://www.springframework.org/schema/util"
xmlns:jee="http://www.springframework.org/schema/jee"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="
    http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context-3.0.xsd
    http://www.springframework.org/schema/mvc
    http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
    http://www.springframework.org/schema/util
    http://www.springframework.org/schema/util/spring-util-3.0.xsd
   http://www.springframework.org/schema/tx
   http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
   http://www.springframework.org/schema/jee
   http://www.springframework.org/schema/jee/spring-jee.xsd">

    <context:annotation-config />
    <context:component-scan base-package="br.com.allinone"/>
        <tx:annotation-driven />
</beans>

当我尝试使用我的服务时，我的控制台中没有收到任何错误消息，只是 nullPointer

当我将 Bean 设为 sessionScoped 时，我收到了这个错误：

com.sun.faces.mgbean.ManagedBeanCreationException: An error occurred when performing resource injection on managed bean homeBean
at com.sun.faces.mgbean.BeanBuilder.invokePostConstruct(BeanBuilder.java:227)
at com.sun.faces.mgbean.BeanBuilder.build(BeanBuilder.java:103)
at com.sun.faces.mgbean.BeanManager.createAndPush(BeanManager.java:409)
at com.sun.faces.mgbean.BeanManager.create(BeanManager.java:269)
at com.sun.faces.el.ManagedBeanELResolver.resolveBean(ManagedBeanELResolver.java:244)
at com.sun.faces.el.ManagedBeanELResolver.getValue(ManagedBeanELResolver.java:116)
at com.sun.faces.el.DemuxCompositeELResolver._getValue(DemuxCompositeELResolver.java:176)
at com.sun.faces.el.DemuxCompositeELResolver.getValue(DemuxCompositeELResolver.java:203)
at org.apache.el.parser.AstIdentifier.getValue(AstIdentifier.java:72)
at org.apache.el.parser.AstValue.getTarget(AstValue.java:94)
at org.apache.el.parser.AstValue.invoke(AstValue.java:245)
at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:278)
at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:87)
at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
at javax.faces.component.UICommand.broadcast(UICommand.java:315)
at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:790)
at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1282)
at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:646)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at com.ocpsoft.pretty.PrettyFilter.doFilter(PrettyFilter.java:145)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:999)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:565)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:309)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)
at java.lang.Thread.run(Thread.java:695)
Caused by: com.sun.faces.spi.InjectionProviderException
at com.sun.faces.vendor.WebContainerInjectionProvider.invokeAnnotatedMethod(WebContainerInjectionProvider.java:115)
at com.sun.faces.vendor.WebContainerInjectionProvider.invokePostConstruct(WebContainerInjectionProvider.java:95)
at com.sun.faces.mgbean.BeanBuilder.invokePostConstruct(BeanBuilder.java:221)
... 40 more
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.sun.faces.vendor.WebContainerInjectionProvider.invokeAnnotatedMethod(WebContainerInjectionProvide    r.java:113)
... 42 more

我的页面 index.xhtml

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"     "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml"
  xmlns:h="http://java.sun.com/jsf/html"
  xmlns:f="http://java.sun.com/jsf/core"
  xmlns:ui="http://java.sun.com/jsf/facelets"> 

<h:head></h:head> 
<body> 
<h:form>
    <h:commandButton value="Log in"  action="#{homeBean.test}" />
</h:form>
</body> 
</html>

【问题讨论】：

请发布更多代码...您是如何调用您的服务的？ UserServiceImpl 和 HomeBean 的包名是什么
哪个类为空？您确定您正确使用了应用程序上下文和 Web 应用程序上下文 (servlet-context.xml) 并且没有任何配置错误吗？异常堆栈跟踪？

标签： java spring code-injection

【解决方案1】：

尝试进行以下更改。

<context:component-scan base-package="br.com.allinone.bean,
br.com.allinone.service,br.com.allinone.service.impl"/>

@Service("userService")
public class UserServiceImpl implements UserService {
}

@Component
@ManagedBean
@URLMapping(id = "homeAdmin", pattern = "/Home", viewId = "/home.jsf")  
public class HomeBean {

    @Autowired
    UserService userService;

}

【讨论】：

你怎么称呼homebean？我在我的回答中进行了更正
我的 HomeBean 是一个 manageBean，所以我从我的 xhtml 中调用它。
它应该可以工作，只要您从上下文中获取 bean。我怀疑这可能是现在的问题...(br.com.allinone.bean)

【解决方案2】：

我终于找到了我的解决方案，我只需在 faces-config.xml 中添加这一行

<application>
    <el-resolver>org.springframework.web.jsf.el.SpringBeanFacesELResolver</el-resolver>
</application>

感谢所有花时间帮助我的人！

【讨论】：