Spring MVC，两个配置实例而不是一个 [英] Spring MVC, two instances of configuration instead of one

问题描述

我开始学习Spring MVC了。我正试图摆脱所有Spring XML配置。这是我的web.xml：

I'm starting to learn about Spring MVC. I'm trying to get rid of all Spring XML configuration. Here is my web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app 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_3_0.xsd"
    version="3.0">
  <!-- Configure ContextLoaderListener to use AnnotationConfigWebApplicationContext
       instead of the default XmlWebApplicationContext -->
  <context-param>
      <param-name>contextClass</param-name>
      <param-value>
          org.springframework.web.context.support.AnnotationConfigWebApplicationContext
      </param-value>
  </context-param>

  <!-- Configuration locations must consist of one or more comma- or space-delimited
       fully-qualified @Configuration classes. Fully-qualified packages may also be
       specified for component-scanning -->
  <context-param>
      <param-name>contextConfigLocation</param-name>
      <param-value>pl.mbrnwsk.sklep.config.AppConfiguration</param-value>
  </context-param>

  <!-- Bootstrap the root application context as usual using ContextLoaderListener -->
  <listener>
      <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
  </listener>

  <!-- Declare a Spring MVC DispatcherServlet as usual -->
  <servlet>
      <servlet-name>dispatcher</servlet-name>
      <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
      <!-- Configure DispatcherServlet to use AnnotationConfigWebApplicationContext
           instead of the default XmlWebApplicationContext -->
      <init-param>
          <param-name>contextClass</param-name>
          <param-value>
              org.springframework.web.context.support.AnnotationConfigWebApplicationContext
          </param-value>
      </init-param>
      <!-- Again, config locations must consist of one or more comma- or space-delimited
           and fully-qualified @Configuration classes -->
      <init-param>
          <param-name>contextConfigLocation</param-name>
          <param-value>pl.mbrnwsk.sklep.config.AppConfiguration</param-value>
      </init-param>
  </servlet>

  <!-- map all requests for / to the dispatcher servlet -->
  <servlet-mapping>
      <servlet-name>dispatcher</servlet-name>
      <url-pattern>/</url-pattern>
  </servlet-mapping>
</web-app>

Appconfiguration.java：

Appconfiguration.java:

@Configuration
@EnableTransactionManagement
@ComponentScan("pl.mbrnwsk.sklep")
public class AppConfiguration {

    public String hbm2ddl_auto = "update";

    public AppConfiguration(){
        System.out.println("AppConfiguration");
    }

    @Bean
    public ViewResolver viewResolver(){
        InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
        viewResolver.setPrefix("/");
        viewResolver.setSuffix(".jsp");
        return viewResolver;
    }

    @Bean
    public DataSource dataSource() {
        DriverManagerDataSource ds = new DriverManagerDataSource();
        ds.setDriverClassName("org.hsqldb.jdbcDriver");
        ds.setUrl("jdbc:hsqldb:file:/SklepDB/");
        ds.setUsername("SA");
        ds.setPassword("");
        return ds;
    }

    @Bean
    public SessionFactory sessionFactory() {
        LocalSessionFactoryBuilder ss = new LocalSessionFactoryBuilder(dataSource());
        ss.scanPackages("pl.mbrnwsk.sklep.model");
        ss.setProperty("hibernate.show_sql", "true");
        ss.setProperty("hibernate.hbm2ddl.auto", hbm2ddl_auto);
        ss.setProperty("hibernate.dialect",
                "org.hibernate.dialect.HSQLDialect");
        return ss.buildSessionFactory();
    }

    @Bean
    public PlatformTransactionManager txManager(){
        return new HibernateTransactionManager(sessionFactory());   
    }
}

AppConfiguration的实例正在创建两次：一次当我启动Tomcat时，当我输入一些应该由调度员处理的URL时。这不是期望的行为。我想在Tomcat启动时创建AppConfiguration。怎么做到这一点？
第二个问题，听众做了什么？

The instance of AppConfiguration is being created two times: once when I start Tomcat and twice when I enter some url that should be handled by dispatcher. This is not desired behaviour. I would like to have AppConfiguration created just with Tomcat start. How to achieve this? And second question, what does listener do?

推荐答案

这里的问题是你使用相同的配置servlet和根上下文。这就是为什么你有两个配置实例。在Spring MVC中，您有两个上下文，即servlet上下文和根上下文。 servlet上下文适用于您的控制器以及业务对象和服务的根上下文。

The problem here is that you are using the same config for the servlet and the root context. Thats why you have two instance of the configuration. In Spring MVC, you have 2 contexts, the servlet context and the root context. The servlet context is for your controllers and the root context for your business objects and your services.

如果您不想使用XML，请创建两个配置类。这样的事情：

If you don't want to use XML, create two config classes. Something like this :

根上下文：

@Configuration
@EnableTransactionManagement
@ComponentScan("pl.mbrnwsk.sklep")
public class AppConfiguration {

    public String hbm2ddl_auto = "update";

    public AppConfiguration(){
        System.out.println("AppConfiguration");
    }

    @Bean
    public DataSource dataSource() {
        DriverManagerDataSource ds = new DriverManagerDataSource();
        ds.setDriverClassName("org.hsqldb.jdbcDriver");
        ds.setUrl("jdbc:hsqldb:file:/SklepDB/");
        ds.setUsername("SA");
        ds.setPassword("");
        return ds;
    }

    @Bean
    public SessionFactory sessionFactory() {
        LocalSessionFactoryBuilder ss = new LocalSessionFactoryBuilder(dataSource());
        ss.scanPackages("pl.mbrnwsk.sklep.model");
        ss.setProperty("hibernate.show_sql", "true");
        ss.setProperty("hibernate.hbm2ddl.auto", hbm2ddl_auto);
        ss.setProperty("hibernate.dialect",
                "org.hibernate.dialect.HSQLDialect");
        return ss.buildSessionFactory();
    }

    @Bean
    public PlatformTransactionManager txManager(){
        return new HibernateTransactionManager(sessionFactory());   
    }
}

Servlet上下文：

@Configuration
@ComponentScan("pl.mbrnwsk.sklep.controller")
public class ServletConfiguration {

    public AppConfiguration(){
        System.out.println("ServletConfiguration");
    }

    @Bean
    public ViewResolver viewResolver(){
        InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
        viewResolver.setPrefix("/");
        viewResolver.setSuffix(".jsp");
        return viewResolver;
    }
}

Web.xml ：

<?xml version="1.0" encoding="UTF-8"?>
<web-app 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_3_0.xsd"
        version="3.0">
      <!-- Configure ContextLoaderListener to use AnnotationConfigWebApplicationContext
           instead of the default XmlWebApplicationContext -->
      <context-param>
          <param-name>contextClass</param-name>
          <param-value>
              org.springframework.web.context.support.AnnotationConfigWebApplicationContext
          </param-value>
      </context-param>

      <!-- Configuration locations must consist of one or more comma- or space-delimited
           fully-qualified @Configuration classes. Fully-qualified packages may also be
           specified for component-scanning -->
      <context-param>
          <param-name>contextConfigLocation</param-name>
          <param-value>pl.mbrnwsk.sklep.config.AppConfiguration</param-value>
      </context-param>

      <!-- Bootstrap the root application context as usual using ContextLoaderListener -->
      <listener>
          <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
      </listener>

      <!-- Declare a Spring MVC DispatcherServlet as usual -->
      <servlet>
          <servlet-name>dispatcher</servlet-name>
          <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
          <!-- Configure DispatcherServlet to use AnnotationConfigWebApplicationContext
               instead of the default XmlWebApplicationContext -->
          <init-param>
              <param-name>contextClass</param-name>
              <param-value>
                  org.springframework.web.context.support.AnnotationConfigWebApplicationContext
              </param-value>
          </init-param>
          <!-- Again, config locations must consist of one or more comma- or space-delimited
               and fully-qualified @Configuration classes -->
          <init-param>
              <param-name>contextConfigLocation</param-name>
              <param-value>pl.mbrnwsk.sklep.config.ServletConfiguration</param-value>
          </init-param>
      </servlet>

      <!-- map all requests for / to the dispatcher servlet -->
      <servlet-mapping>
          <servlet-name>dispatcher</servlet-name>
          <url-pattern>/</url-pattern>
      </servlet-mapping>
</web-app>

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