08 spring integrated web

First look at the use of the spring, and in 02 to write the first spring program when the first add spring-context-dependent, create a bean in spring-context.xml file, the first new use of a container, and then get out of the container. Now, to integrate the web, the purpose is to load ApplicationContext when the program started, use the no longer new.

Starting container to be automatically loaded when  ApplicationContext, Spring provides  ContextLoaderListener is to automatically assemble  ApplicationContext configuration information

pom.xml introduced in dependence on the spring-web

<dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>4.3.17.RELEASE</version>
</dependency>
<dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>3.5</version>
</dependency>

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         version="3.1">

    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:spring-context.xml</param-value>
    </context-param>
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
</web-app>

SpringContext.java

When a class implements this interface ( ApplicationContextAwarelater), this class you can easily get  ApplicationContext all the bean. In other words, this class can directly obtain the Spring configuration file, there are references to all of Bean object.

package com.example.my.shop.commons.context;

import org.apache.commons.lang3.Validate;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;

public class SpringContext implements ApplicationContextAware, DisposableBean {

    private static final Logger logger = LoggerFactory.getLogger(SpringContext.class);

    private static ApplicationContext applicationContext;

    /**
     * 获取存储在静态变量中的 ApplicationContext
     * @return
     */
    public static ApplicationContext getApplicationContext() {
        assertContextInjected();
        return applicationContext;
    }

    /**
     * 从静态变量 applicationContext 中获取 Bean，自动转型成所赋值对象的类型
     * @param name
     * @param <T>
     * @return
     */
    public static <T> T getBean(String name) {
        assertContextInjected();
        return (T) applicationContext.getBean(name);
    }

    /**
     * 从静态变量 applicationContext 中获取 Bean，自动转型成所赋值对象的类型
     * @param clazz
     * @param <T>
     * @return
     */
    public static <T> T getBean(Class<T> clazz) {
        assertContextInjected();
        return applicationContext.getBean(clazz);
    }

    /**
     * 实现 DisposableBean 接口，在 Context 关闭时清理静态变量
     * @throws Exception
     */
    public void destroy() throws Exception {
        logger.debug("清除 SpringContext 中的 ApplicationContext: {}", applicationContext);
        applicationContext = null;
    }

    /**
     * 实现 ApplicationContextAware 接口，注入 Context 到静态变量中
     * @param applicationContext
     * @throws BeansException
     */
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        SpringContext.applicationContext = applicationContext;
    }

    /**
     * 断言 Context 已经注入
     */
    private static void assertContextInjected() {
        Validate.validState(applicationContext != null, "applicationContext 属性未注入，请在 spring-context.xml 配置中定义 SpringContext");
    }
}

 Also you need to  spring-context.xml assemble the configuration file  <bean id="springContext" class="com.funtl.leeshop.commons.context.SpringContext" />;

Note: Please configure the Bean on the top, otherwise it will error when using

spring-context.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       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">

    <bean id="springContext" class="com.example.my.shop.commons.context.SpringContext" />
    <bean id="userDao" class="com.example.my.shop.dao.impl.UserDaoImpl" />
    <bean id="userService" class="com.example.my.shop.service.impl.UserServiceImpl"/>

</beans>

Then you can get a bean!