Spring集成Web环境的实例详解

Spring整合Web开发需要导入的坐标

<properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>11</maven.compiler.source>
        <maven.compiler.target>11</maven.compiler.target>
    </properties>

<build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.1</version>
                <configuration>
                    <release>11</release>
                </configuration>
            </plugin>
        </plugins>
    </build>

<dependencies>
<!--        下面是web开发需要的依赖-->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>servlet-api</artifactId>
            <version>3.1.0</version>
        </dependency>

<!--        下面是spring依赖-->
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.2.4.RELEASE</version>
<!--        下面两个是spring整和Web需要的坐标-->
            <artifactId>javax.servlet-api</artifactId>
            <scope>provided</scope>
            <groupId>Maven_Repository.javax.servlet.jsp</groupId>
            <artifactId>javax.servlet.jsp-api</artifactId>
            <version>2.3.1</version>
<!--        下面是上下文应用整和的坐标-->
            <artifactId>spring-web</artifactId>
            <version>5.0.5.RELEASE</version>
            <groupId>Maven_Repository.com.h2database</groupId>
            <artifactId>h2</artifactId>
            <version>1.3.158</version>
    </dependencies>

① 配置ContextLoaderListener监听器
② 使用WebApplicationContextUtils获得应用上下文

获取ApplicationContext对象是从servletContext域中获取的，还有就是使用WebApplicationContextUtils获取app。 可以直接从Spring获取app对象，省去了自己创建。还有就是以后要使用到多次app对象，所以就是省去了new出多了app对象。

dao层代码

package com.itheima.dao.impl;

import com.itheima.dao.UserDao;
public class UserDaoImpl implements UserDao {
    public void save() {
        System.out.println("save is running");
    }
}

service层代码

package com.itheima.service.impl;

import com.itheima.dao.UserDao;
import com.itheima.service.UserService;
public class UserServiceImpl implements UserService {
    private UserDao userDao;

    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }
    public void save() {
        userDao.save();
}

web层

package com.itheima.web;

import com.itheima.service.UserService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/servlet")
public class UserServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//        ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
        ServletContext servletContext = this.getServletContext();
//         ApplicationContext app = (ApplicationContext) servletContext.getAttribute("app");
//        ApplicationContext app = WebApplicationContextUtils.getWebApplicationContext(servletContext);
        ApplicationContext app = WebApplicationContextUtils.getWebApplicationContext(servletContext);
        UserService userService = (UserService) app.getBean("userService");
        userService.save();
    }
}

applicationContext.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="userDao" class="com.itheima.dao.impl.UserDaoImpl"></bean>
    <bean id="userService" class="com.itheima.service.impl.UserServiceImpl">
        <property name="userDao" ref="userDao"></property>
    </bean>
</beans>

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_4_0.xsd"
         version="4.0">
    <!--全局初始化参数-->
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:applicationContext.xml</param-value>
    </context-param>
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
</web-app>

问题：

在配置maven时候，project下面有红色波浪线的话，可能是复制的坐标，需要重写写一遍，还有就是是maven可能是3.6.3版本，idea和maven可能会出现冲突，所以要降低maven版本，改为3.6.1版本即可。

在部署tomcat的时候，可能回出现监听器的问题，如果是tomcat10，就需要降低tomcat版本，如果是tomcat8.5.5及其一下的版本，就需要做一下操作。

就会出现lib包，再重新部署一下项目就可以了。

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