Question

我正在尝试自动安装RestTemplate，我正在使用why can I autowire or inject pojo but I can't autowire or inject RestTemplate中的建议。不幸的是，我遇到了第二次实例化的问题。变量restTemplate只能运行一次。之后，它为空。我想我可能在dispatcher-servlet或web.xml配置中犯了一些错误。

我知道范围原型每次调用时都会创建一个新实例，但我不希望自动连线RestTemplate在第二个实例中为空。所有其他自动变量变量在每次调用时都能完美运行我看到了一些类似的线程，所有这些线程最终得到了一些与创建范围代理相关的解决方案。我改为@Scope(value="prototype", proxyMode = ScopedProxyMode.TARGET_CLASS)但我得到错误“只能在引用原型bean定义时为getBean方法指定参数”。老实说，我无法想象这是我的情况的正确方向，因为我只有restTemplate和context.getBean的第二个问题。

//the process starts here

    ApplicationContext context = WebApplicationContextUtils.getRequiredWebApplicationContext(getServletContext());
                   display = context.getBean(Lo_DisplayHandler.class, request, response);

                         display.lastPage();

DisplayHandler

@Component
@Scope("prototype")
public class Lo_DisplayHandler extends Lo_Handler {
 //this constructor runs twice when the application start
       public Lo_DisplayHandler() {
              super();
       }

每次从上下文获取bean时都会运行此构造函数（context.getBean（Lo_DisplayHandler.class，request，response））。第一次创建Lo_DisplayHandler时，会填充restTemplate，但是从第二次开始，restTemplate为null

public Lo_DisplayHandler(HttpServletRequest request,HttpServletResponse response) {
    super();
    //get DB2 connection and set some data in session
}


@Autowired
private RestTemplate restTemplate;
 //restTemplate will exist only in the first time
LogDisplay _l = restTemplate.postForObject(RestProperties.getUrl() + RestProperties.getFirstpage(),_mas60010, LogDisplay.class);

MVC-调度-servlet.xml中

    <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: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
            http://www.springframework.org/schema/context
            http://www.springframework.org/schema/context/spring-context.xsd
            http://www.springframework.org/schema/mvc
            http://www.springframework.org/schema/mvc/spring-mvc.xsd">

           <context:annotation-config />
           <mvc:annotation-driven />
           <context:component-scan base-package="com.myCompany.mhe.common.controller, com.myCompany.mhe.log.handler, com.myCompany.mhe.utilities, com.myCompany.mhe.log.domain, com.myCompany.mhe.log.storedprocedure" />
           <context:property-placeholder location="classpath:restServices.properties"/>
           <mvc:resources mapping="/**" location="/" />

           <!—-
    If take the next three beans definition from here to applicationContext.xml and change contextConfigLocation to point to applicationContext.xml instead of mvc-dispatcher-servlet.xml my controller stops to work
    -->

           <bean id="jacksonObjectMapper" class="com.fasterxml.jackson.databind.ObjectMapper" />
           <bean
               class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
               <property name="targetObject" ref="jacksonObjectMapper" />
               <property name="targetMethod" value="configure" />
               <property name="arguments">
                   <list>
                       <value type="com.fasterxml.jackson.databind.DeserializationFeature">READ_DATE_TIMESTAMPS_AS_NANOSECONDS</value>
                       <value>true</value>
                   </list>
               </property>
           </bean>

           <bean id="restTemplate" class="org.springframework.web.client.RestTemplate">
               <property name="messageConverters">
                   <list>
                       <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
                           <property name="objectMapper" ref="jacksonObjectMapper" />
                       </bean>
                   </list>
               </property>
           </bean>


    </beans>

的web.xml

  <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>

   <context-param>
          <param-name>contextConfigLocation</param-name>
          <param-value>/WEB-INF/mvc-dispatcher-servlet.xml</param-value>
   </context-param>

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

//删除默认构造函数后的异常

[WARNING ] Exception encountered during context initialization - cancelling refresh attempt
Error creating bean with name 'lo_Controller': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.mycompany.mhe.Mhe_Handler com.mycompany.mhe.common.controller.Lo_Controller.mhe_Handler; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'lo_DisplayHandler' defined in file [C:\STS\wsRestTemplate\MHE_original\WebContent\WEB-INF\classes\com\mycompany\mhe\log\handler\Lo_DisplayHandler.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.mycompany.mhe.log.handler.Lo_DisplayHandler]: No default constructor found; nested exception is java.lang.NoSuchMethodException: com.mycompany.mhe.log.handler.Lo_DisplayHandler.<init>()
[ERROR   ] Context initialization failed
Error creating bean with name 'lo_Controller': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.mycompany.mhe.Mhe_Handler com.mycompany.mhe.common.controller.Lo_Controller.mhe_Handler; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'lo_DisplayHandler' defined in file [C:\STS\wsRestTemplate\MHE_original\WebContent\WEB-INF\classes\com\mycompany\mhe\log\handler\Lo_DisplayHandler.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.mycompany.mhe.log.handler.Lo_DisplayHandler]: No default constructor found; nested exception is java.lang.NoSuchMethodException: com.mycompany.mhe.log.handler.Lo_DisplayHandler.<init>()

为什么原型范围中的自动装配变量仅在第一个实例中起作用

0 个答案: