java Spring单例被调用两次
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Spring singleton being called twice
提问by Faisal Basra
getting some problem into my spring application.
在我的 spring 应用程序中遇到了一些问题。
I have very fairly simple spring beans, they are injected into various other spring beans. While debugging I found, they are being called twice, Constructor & @PostConstruct both called two times.
我有非常简单的春豆，它们被注入到其他各种春豆中。在调试时我发现，它们被调用了两次，Constructor 和 @PostConstruct 都被调用了两次。
My application have no front end technology. Its simply for backend task related.
我的应用程序没有前端技术。它只是与后端任务相关。
Spring Configuration
弹簧配置
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:lang="http://www.springframework.org/schema/lang" xmlns:p="http://www.springframework.org/schema/p"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-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/lang http://www.springframework.org/schema/lang/spring-lang.xsd">
<context:component-scan base-package="com.green.integration" />
<!-- ######################################################## -->
<!-- EXPOSING SPRING BEAN VIA HTTPINVOKER SPRING REMOTING -->
<!-- ######################################################## -->
<bean name="/switch"
class="org.springframework.remoting.httpinvoker.HttpInvokerServiceExporter">
<property name="service" ref="SwitchController" />
<property name="serviceInterface"
value="com.green.ISwitchController" />
</bean>
<!-- Load in application properties reference -->
<bean id="applicationProperties"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="location" value="classpath:application.properties" />
</bean>
<bean id="mongo" class="com.mongodb.Mongo">
<constructor-arg value="${mongo.server}" />
<constructor-arg value="${mongo.port}" />
</bean>
<bean id="morphia" class="com.google.code.morphia.Morphia">
</bean>
</beans>
Spring Bean Class
春豆类
@Repository
public class TransactionDAO extends BasicDAO<Transaction, ObjectId> {
private Datastore datastore;
@Autowired
public TransactionDAO(Mongo mongo, Morphia morphia) {
super(mongo, morphia, "itransact");
morphia.map(Transaction.class);
// TO USE MONGO WITHOUT SECURITY
this.datastore = morphia.createDatastore(mongo, "itransact");
logger.debug("***** CONNECTED TO MONGODB SUCCESSFULLY *****");
this.datastore.ensureIndexes();
// this.datastore.ensureCaps();
}
}
Constructor "TransactionDAO" is being called twice.
构造函数“TransactionDAO”被调用两次。
I tried to watch call stack trace by
我试图通过以下方式观看调用堆栈跟踪
Throwable t = new Throwable();
System.out.println(t.getStackTrace()[1].toString());
and each time it showed the following
并且每次显示以下内容
sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
回答by Faisal Basra
I just figured out the problem and special thanks to @Juan Alberto who give me hint to the problem.
我刚刚解决了这个问题，特别感谢@Juan Alberto，他给了我这个问题的提示。
Description: Actually I was giving the one applicationContext.xml file for both contextListner and dispatcher servlet. So 1st bean was initializing for spring core and 2nd time for spring dispatcher.
描述：实际上，我为 contextListner 和调度程序 servlet 提供了一个 applicationContext.xml 文件。所以第一个 bean 为 spring 核心初始化，第二次为 spring 调度程序初始化。
I spilt the configuration now, into applicationContext.xml and applicationContext-dispatcher.xml which have only their relevant configurations and my beans are initializing once properly.
我现在将配置溢出到 applicationContext.xml 和 applicationContext-dispatcher.xml 中，它们只有它们的相关配置，并且我的 bean 正在正确初始化一次。
Problematic Configs
有问题的配置
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/applicationContext.xml</param-value>
</context-param>
<servlet>
<servlet-name>remoting</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/applicationContext.xml</param-value>
</init-param>
<load-on-startup>0</load-on-startup>
</servlet>
Solved Configs
已解决的配置
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/applicationContext.xml</param-value>
</context-param>
<servlet>
<servlet-name>remoting</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/applicationContext-dispatcher.xml</param-value>
</init-param>
<load-on-startup>0</load-on-startup>
</servlet>
回答by Juan Alberto López Cavallotti
Actually your issue is that you may be defining the beans in the dispatcher servlet and also your spring context, the dispatcher provides a different context but It (a sub context I think) of the main context so the right way to do things is having your main context scan your "model classes" and the dispatcher just only scan for the controllers.
实际上，您的问题是您可能在调度程序 servlet 和 spring 上下文中定义了 bean，调度程序提供了不同的上下文，但是它（我认为是一个子上下文）是主上下文，因此正确的做事方法是让您的主上下文扫描您的“模型类”，调度程序只扫描控制器。
I hope this helps you.
我希望这可以帮助你。
