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问为什么我可以自动或注入pojo，但我不能自动或注入RestTemplate
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Stack Overflow用户

提问于 2014-12-16 20:37:13

回答 1查看 4.7K关注 0票数 0

我在这个论坛上读到了很多关于在尝试使用pojo时发生的类似问题的文章，而修复的答案通常与component-scan或@Component/@Controller有关。但在我的例子中，我设法自动读取了我的pojo (Mas60010)，但是我不能从一个没有编写代码的包中自动生成RestTemplate或ObjectMapper，可能还有任何其他对象。

简单地说，我只提到RestTemplate。我做错什么了？我想问题要么在于库，要么是配置。注意:请不要仅仅通过显示一个与他自己的pojo相关的问题来指出这个问题是重复的。你可以看到，这不是我的问题，因为我有能力做到这一点。问题是jars中的类包含在我的项目中。

package com.ma.mhe.log.handler;

import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.web.client.RestTemplate;

@Component
public class Lo_DisplayHandler extends Lo_Handler {

       @Autowired private Mas60010 _mas60010; //this work perfectly
       @Autowired private RestTemplate restTemplate; //this always cause nullPointException

mvc-dispatcher-servlet.xml

<context:annotation-config />
<mvc:annotation-driven />
<context:component-scan base-package="com.ma.mhe.log.handle, com.ma.mhe.log.domain" />
<context:property-placeholder location="classpath:restServices.properties"/>

<mvc:resources mapping="/**" location="/" />

<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    <property name="prefix">
        <value>/WEB-INF/pages/</value>
    </property>
    <property name="suffix">
        <value>.jsp</value>
    </property>
</bean>

<bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
    <property name="messageConverters">
        <list>
            <ref bean="jsonMessageConverter"/>
        </list>
    </property>
</bean>

<bean id="jsonMessageConverter" class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
</bean>

<!-- I was expecting this line to be enouth -->   
<bean id="restTemplate" class="org.springframework.web.client.RestTemplate">
</bean>

//Pojo -我可以自动完成它

package com.ma.log.domain;

import org.springframework.stereotype.Service;

@Service
public class Mas60010 {

所有图书馆

“验证-api-1.0.0.GA.jar”
“联盟-1.0.jar”
公用-日志-1.1.1.jar
"db2java.zip“
hibernate-验证器-4.1.0.Final.jar
"hibernate-validator-annotation-processor-4.1.0.Final.jar“
“jackson-注释-2.2.3.jar”
杰克逊-核心-2.2.3.jar
杰克逊数据库-2.2.3.jar
"slf4j-api-1.7.5.jar“
弹簧-AOP-4.1.2.RELEASE.jar
春豆-4.1.2.RELEASE.JAR
“spring-上下文-4.1.2.RELEASE.jar”
“spring-上下文-支持-4.1.2.RELEASE.jar”
弹簧-核心-4.1.2.RELEASE.JAR
“spring-表达式-4.1.2.RELEASE.jar”
"spring-web-4.1.2.RELEASE.jar“
"spring-webmvc-4.1.2.RELEASE.jar“
"upload.jar“

//StackTrace

[12/17/14 10:38:54:243 CST] 00000033 SystemErr                                                    R        at com.ma.mhe.log.handler.Lo_DisplayHandler.lastPage(Lo_DisplayHandler.java:181)
[12/17/14 10:38:54:246 CST] 00000033 SystemErr                                                    R        at com.ma.mhe.log.Lo_Servlet.doDisDis(Lo_Servlet.java:164)
[12/17/14 10:38:54:248 CST] 00000033 SystemErr                                                    R        at com.ma.mhe.log.Lo_Servlet.doProcess(Lo_Servlet.java:51)
[12/17/14 10:38:54:250 CST] 00000033 SystemErr                                                    R        at com.ma.mhe.log.Lo_Servlet.doPost(Lo_Servlet.java:24)
[12/17/14 10:38:54:253 CST] 00000033 SystemErr                                                    R        at javax.servlet.http.HttpServlet.service(HttpServlet.java:595)
[12/17/14 10:38:54:255 CST] 00000033 SystemErr                                                    R        at javax.servlet.http.HttpServlet.service(HttpServlet.java:668)
[12/17/14 10:38:54:257 CST] 00000033 SystemErr                                                    R        at com.ibm.ws.webcontainer.servlet.ServletWrapper.service(ServletWrapper.java:1274)
[12/17/14 10:38:54:260 CST] 00000033 SystemErr                                                    R        at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:767)
[12/17/14 10:38:54:261 CST] 00000033 SystemErr                                                    R        at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:469)
[12/17/14 10:38:54:262 CST] 00000033 SystemErr                                                    R        at com.ibm.ws.webcontainer.filter.WebAppFilterManager.invokeFilters(WebAppFilterManager.java:1060)
[12/17/14 10:38:54:263 CST] 00000033 SystemErr                                                    R        at com.ibm.ws.webcontainer.webapp.WebAppRequestDispatcher.dispatch(WebAppRequestDispatcher.java:1377)
[12/17/14 10:38:54:265 CST] 00000033 SystemErr                                                    R        at com.ibm.ws.webcontainer.webapp.WebAppRequestDispatcher.forward(WebAppRequestDispatcher.java:185)
[12/17/14 10:38:54:266 CST] 00000033 SystemErr                                                    R        at com.ma.mhe.Mhe_ControllerServlet.doProcess(Mhe_ControllerServlet.java:83)
[12/17/14 10:38:54:267 CST] 00000033 SystemErr                                                    R        at com.ma.mhe.Mhe_ControllerServlet.doPost(Mhe_ControllerServlet.java:32)
[12/17/14 10:38:54:268 CST] 00000033 SystemErr                                                    R        at javax.servlet.http.HttpServlet.service(HttpServlet.java:595)
[12/17/14 10:38:54:269 CST] 00000033 SystemErr                                                    R        at javax.servlet.http.HttpServlet.service(HttpServlet.java:668)
[12/17/14 10:38:54:270 CST] 00000033 SystemErr                                                    R        at com.ibm.ws.webcontainer.servlet.ServletWrapper.service(ServletWrapper.java:1274)
[12/17/14 10:38:54:271 CST] 00000033 SystemErr                                                    R        at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:767)
[12/17/14 10:38:54:272 CST] 00000033 SystemErr                                                    R        at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:469)
[12/17/14 10:38:54:273 CST] 00000033 SystemErr                                                    R        at com.ibm.ws.webcontainer.filter.WebAppFilterManager.invokeFilters(WebAppFilterManager.java:1060)
[12/17/14 10:38:54:275 CST] 00000033 SystemErr                                                    R        at com.ibm.ws.webcontainer.servlet.CacheServletWrapper.handleRequest(CacheServletWrapper.java:81)
[12/17/14 10:38:54:276 CST] 00000033 SystemErr                                                    R        at com.ibm.ws.webcontainer.WebContainer.handleRequest(WebContainer.java:885)
[12/17/14 10:38:54:277 CST] 00000033 SystemErr                                                    R        at com.ibm.ws.webcontainer.osgi.DynamicVirtualHost$2.run(DynamicVirtualHost.java:266)
[12/17/14 10:38:54:277 CST] 00000033 SystemErr                                                    R        at com.ibm.ws.http.dispatcher.internal.channel.HttpDispatcherLink$TaskWrapper.run(HttpDispatcherLink.java:776)
[12/17/14 10:38:54:278 CST] 00000033 SystemErr                                                    R        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)
[12/17/14 10:38:54:279 CST] 00000033 SystemErr                                                    R        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)
[12/17/14 10:38:54:280 CST] 00000033 SystemErr                                                    R        at java.lang.Thread.run(Thread.java:662)

启用WebSphere自由配置文件的特性

<featureManager>
        <feature>jsp-2.2</feature>
        <feature>localConnector-1.0</feature>
        <feature>jdbc-4.0</feature>
        <feature>jaxrs-1.1</feature>
        <feature>json-1.0</feature>
        <feature>cdi-1.0</feature>
        <feature>managedBeans-1.0</feature>
        <feature>beanValidation-1.0</feature>
</featureManager>

//类Lo_DisplayHandler

@Component
public class Lo_DisplayHandler extends Lo_Handler {

       public Lo_DisplayHandler() {
              super();
       }

       @Autowired
       private Mas60010 _mas60010;
       @Autowired private RestTemplate restTemplate;


       public Lo_DisplayHandler(HttpServletRequest request,HttpServletResponse response) {
              super();

              this.request  = request;
              this.response = response;
       }



       public void lastPage() {
              //RestTemplate restTemplate = new RestTemplate(); //if I uncomment this line and comment the @Autowired it will work
              ObjectMapper mapper = new ObjectMapper();
              try{


                     myPojoParameters...       

                     //the next line rises nullPointExcepetion if I choose Autowired instead of new RestTemplate()
                     LogDisplay _l = restTemplate.postForObject(myServiceUrl,myPojoParameters, LogDisplay.class);
                     Lo_DisplayRecord lo_DisplayRecord = new Lo_DisplayRecord();

                     ArrayList<Lo_DisplayRecord> displayValues = new ArrayList<Lo_DisplayRecord>();

                     for(int i = 0; i < _l.getDisplayValues().size(); i++){
                           lo_DisplayRecord = mapper.convertValue(_l.getDisplayValues().get(i), Lo_DisplayRecord.class);
                           displayValues.add(lo_DisplayRecord);
                     }

                     Some not relevant operations...                
              }catch(Exception e){
                     e.printStackTrace();

//Lo_Servlet

package com.ma.mhe.log;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import com.ma.mhe.Mhe_Servlet;
import com.ma.mhe.PageFlow;
import com.ma.mhe.log.handler.*;

public class Lo_Servlet extends Mhe_Servlet {


                private String _module = "lo       public void init(){}

                public void doPost(
                                javax.servlet.http.HttpServletRequest request,
                                javax.servlet.http.HttpServletResponse response)
                                throws javax.servlet.ServletException, java.io.IOException {
                                doProcess(request,response);                                                 
                }

                public void doGet(
                                javax.servlet.http.HttpServletRequest request,
                                javax.servlet.http.HttpServletResponse response)
                                throws javax.servlet.ServletException, java.io.IOException {
                                doProcess(request,response); 
                }
                public void doProcess(
                                javax.servlet.http.HttpServletRequest request,
                                javax.servlet.http.HttpServletResponse response)
                                throws javax.servlet.ServletException, java.io.IOException {
                                HttpSession session = request.getSession();
                                int val = setTask(session,request);

                                switch(val){

                                //FILTER PAGE
                                case 1:doFilRep(request,response);break;                                                                                                                                                         
                                case 2:doFilFil(request,response);break;                            
                                case 3:doFilDis(request,response);break;           
                                case 4:doFilDef(request,response);break;

                                //DISPLAY PAGE
                                case 5:doDisRep(request,response);break;                                                                                                                                                        
                                case 6:doDisFil(request,response);break;           
                                case 7:doDisDis(request,response);break;

       private void doDisDis(HttpServletRequest request,HttpServletResponse response){

              Lo_DisplayHandler display = null;
              try{
                     display = new Lo_DisplayHandler(request,response);

                     display.lastPage();
              }catch(Exception e){
                                   }finally{
                     display = null;
              }


       }

//web.xml ">4.xsd"> MHE

       <servlet>
              <servlet-name>mvc-dispatcher</servlet-name>
              <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
              <load-on-startup>1</load-on-startup>
       </servlet>

       <servlet-mapping>
              <servlet-name>mvc-dispatcher</servlet-name>
              <url-pattern>/</url-pattern>
       </servlet-mapping>

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

    <servlet>
        <servlet-name>myservice</servlet-name>
        <servlet-class>org.springframework.ws.transport.http.MessageDispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
                     <param-value>/WEB-INF/mvc-dispatcher-servlet.xml</param-value>
        </init-param>
    </servlet>      

       <servlet>
              <description>
              </description>
              <display-name>Lo_Servlet</display-name>
              <servlet-name>Lo_Servlet</servlet-name>
              <servlet-class>com.ma.mhe.log.Lo_Servlet</servlet-class>

       </servlet>
... others servlets configuration like this

spring

dependency-injection

回答 1

Stack Overflow用户

回答已采纳

发布于 2014-12-18 19:13:25

private void doDisDis(HttpServletRequest request,HttpServletResponse response){
    Lo_DisplayHandler display = null;
    try {
        display = new Lo_DisplayHandler(request,response);
        display.lastPage();
    }catch(Exception e){
    }finally{
        display = null;
    }
}

上面的代码是创建Lo_DisplayHandler类的新实例。这些实例不是由Spring管理的，因此基本上@Autowired在这里是无用的。Spring只会将依赖注入到它所知道的bean中。

假设使用ContextLoaderListener加载spring配置，则可以使用WebApplicationContextUtils获取ApplicationContext。你可以用这个得到你想要的豆子。

private void doDisDis(HttpServletRequest request,HttpServletResponse response){
    Lo_DisplayHandler display = null;
    try {
        ApplicationContext context = WebApplicationContextUtils.getRequiredWebApplicationContext(getServletContext());          
        display = context.getBean(Lo_DisplayHandler.class, request, response);
        display.lastPage();
    }catch(Exception e){
    }finally{
        display = null;
    }
}

要完成这项工作，您必须使Lo_DisplayHandler成为一个原型bean，这意味着每次执行getBean调用时，都会创建一个新实例。为此，向类添加@Scope注释。

@Component
@Scope("prototype")
public class Lo_DisplayHandler extends Lo_Handler { ... }

最后一个注意事项不是每次需要查找ApplicationContext，而是希望在servlet的init方法中进行一次查找，并将其存储为实例变量。节省了一行代码和一些性能。

票数 0

页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持

原文链接：

https://stackoverflow.com/questions/27513495

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