在普通WEB项目中使用Spring

Spring是一个对象容器,帮助我们管理项目中的对象,那么在web项目中哪些对象应该交给Spring管理呢?

项目中涉及的对象

​ 我们回顾一下WEB项目中涉及的对象

• Servlet
• Request
• Response
• Session
• Service
• DAO
• POJO

分析

我们在学习IOC容器时知道,Spring可以帮助我们管理原来需要自己创建管理的对象,如果一个对象原来就不需要我们自行管理其的创建和声明周期的话,那么该对象也就不需要交给Spring管理

由此来看,上述对象中只有Service,DAO,POJO应该交给Spring管理,而由于POJO通常都是由持久层框架动态创建的,所以最后只有Service和DAO要交给Spring容器管理,

当然Spring中的AOP也是很常用的功能,例如事务管理,日志输出等..

最小pom依赖:

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.7</maven.compiler.source>
        <maven.compiler.target>1.7</maven.compiler.target>
    </properties>

    <dependencies>
        <!--    spring核心容器-->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.2.2.RELEASE</version>
        </dependency>
        <!--      spring-web-->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>5.2.2.RELEASE</version>
        </dependency>

        <!--web相关的-->
        <!-- https://mvnrepository.com/artifact/javax.servlet/jstl -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/javax.servlet.jsp/javax.servlet.jsp-api -->
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>javax.servlet.jsp-api</artifactId>
            <version>2.3.3</version>
            <scope>provided</scope>
        </dependency>
        <!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>4.0.1</version>
            <scope>provided</scope>
        </dependency>
    </dependencies>

上述依赖可以保证项目可以使用Spring容器以及JSP,EL,Servlet的正常使用,测试完成后既可以向普通Spring或web项目一样进行开发了

Spring配置文件:

<?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">
<!--    测试bean-->
    <bean id="integer" class="java.lang.Integer">
        <constructor-arg type="java.lang.String" value="100"/>
    </bean>
</beans>

在容器中添加了一个整数,用于测试容器是否可用

web.xml

<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app version="2.5"
         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_2_5.xsd">

  <display-name>Archetype Created Web Application</display-name>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>

<!--  spring配置文件:-->
  <context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>classpath:applicationContext.xml</param-value>
  </context-param>
<!--  spring监听器 使得容器随着项目启动:-->
  <listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
  </listener>

</web-app>

测试Servlet

package com.yh.servlet;

import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;

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(name = "TestServlet",urlPatterns = "/test")
public class TestServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //获取Spring容器
        WebApplicationContext context = WebApplicationContextUtils.getWebApplicationContext(getServletContext());
        //获取容器中的对象测试
        Object integer = context.getBean("integer");
        response.getWriter().println("hello spring "+integer);
    }
}

配置tomcat启动访问:http://localhost:8080/HMWK_war_exploded/test即可查看到容器中的整数100,表明Spring和WEB项目都正常工作了!