Spring的web集成 (Spring监听器)

Maven项目-jar包冲突：MyServlet is not a Servlet解决方法

Spring访问传统的Servlet

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web.xml


<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">
    <servlet>
        <servlet-name>HelloServletservlet-name>
        <servlet-class>cn.itcast.spring.servlet.HelloServletservlet-class>
    servlet>
    <servlet-mapping>
        <servlet-name>HelloServletservlet-name>
        <url-pattern>/helloservleturl-pattern>
    servlet-mapping>
web-app>
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HelloService.java

package cn.itcast.spring.service;

public class HelloService {
    public void sayHello(){
        System.out.println("嘿，传智播客。。。。");
    }
}
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HelloServlet.java

package cn.itcast.spring.servlet;

import cn.itcast.spring.service.HelloService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class HelloServlet extends HttpServlet {

    @Override
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        //传统方式：
        //new service
        //HelloService helloService = new HelloService();
        //spring方式：只要看到new，你就想到spring容器中的
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
        HelloService helloService=(HelloService)applicationContext.getBean("helloService");
        System.out.println("helloService = " + helloService);
        helloService.sayHello();
    }

    @Override
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        this.doGet(request, response);
    }
}
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applicationContext.xml


<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       					   http://www.springframework.org/schema/beans/spring-beans.xsd
						   http://www.springframework.org/schema/context
						   http://www.springframework.org/schema/context/spring-context.xsd">

    
    <bean id="helloService" class="cn.itcast.spring.service.HelloService"/>
beans>
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log4j.properties

log4j.rootLogger=INFO,A1
log4j.logger.org.apache=INFO
log4j.appender.A1.Target=System.err
log4j.appender.A1=org.apache.log4j.ConsoleAppender
log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=%-d{yyyy-MM-dd HH:mm:ss,SSS} [%t] [%c]-[%p] %m%n

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pom.xml(itcast-parent)

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
		 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0modelVersion>

	<groupId>cn.itcast.parentgroupId>
	<artifactId>itcast-parentartifactId>
	<version>0.0.1-SNAPSHOTversion>
	<modules>
		<module>mybatismodule>
		<module>spring4module>
	modules>
	<packaging>pompackaging>

	
	<properties>
		
		<junit.version>4.12junit.version>
		<spring.version>4.3.13.RELEASEspring.version>
		<mybatis.version>3.2.8mybatis.version>
		<mybatis.spring.version>1.2.2mybatis.spring.version>
		<mybatis.paginator.version>1.2.15mybatis.paginator.version>
		<mysql.version>5.1.32mysql.version>
		<slf4j.version>1.6.4slf4j.version>
		<jackson.version>2.9.0jackson.version>
		<druid.version>1.0.9druid.version>
		<httpclient.version>4.3.5httpclient.version>
		<jstl.version>1.2jstl.version>
		<servlet-api.version>2.5servlet-api.version>
		<jsp-api.version>2.0jsp-api.version>
		<joda-time.version>2.5joda-time.version>
		<commons-lang3.version>3.3.2commons-lang3.version>
		<commons-io.version>1.3.2commons-io.version>
	properties>

	<dependencies>

		
		<dependency>
			<groupId>junitgroupId>
			<artifactId>junitartifactId>
			<scope>testscope>
		dependency>


	dependencies>


	
	<dependencyManagement>
		<dependencies>
			
			<dependency>
				<groupId>junitgroupId>
				<artifactId>junitartifactId>
				<version>${junit.version}version>
				<scope>testscope>
			dependency>

			
			<dependency>
				<groupId>org.springframeworkgroupId>
				<artifactId>spring-testartifactId>
				<version>${spring.version}version>
				<scope>testscope>
			dependency>

			
			<dependency>
				<groupId>org.springframeworkgroupId>
				<artifactId>spring-contextartifactId>
				<version>${spring.version}version>
			dependency>
			<dependency>
				<groupId>org.springframeworkgroupId>
				<artifactId>spring-beansartifactId>
				<version>${spring.version}version>
			dependency>
			<dependency>
				<groupId>org.springframeworkgroupId>
				<artifactId>spring-webmvcartifactId>
				<version>${spring.version}version>
			dependency>
			<dependency>
				<groupId>org.springframeworkgroupId>
				<artifactId>spring-jdbcartifactId>
				<version>${spring.version}version>
			dependency>
			<dependency>
				<groupId>org.springframeworkgroupId>
				<artifactId>spring-aspectsartifactId>
				<version>${spring.version}version>
			dependency>

			
			<dependency>
				<groupId>org.mybatisgroupId>
				<artifactId>mybatisartifactId>
				<version>${mybatis.version}version>
			dependency>
			<dependency>
				<groupId>org.mybatisgroupId>
				<artifactId>mybatis-springartifactId>
				<version>${mybatis.spring.version}version>
			dependency>
			<dependency>
				<groupId>com.github.miemiedevgroupId>
				<artifactId>mybatis-paginatorartifactId>
				<version>${mybatis.paginator.version}version>
			dependency>

			
			<dependency>
				<groupId>mysqlgroupId>
				<artifactId>mysql-connector-javaartifactId>
				<version>${mysql.version}version>
			dependency>

			<dependency>
				<groupId>org.slf4jgroupId>
				<artifactId>slf4j-log4j12artifactId>
				<version>${slf4j.version}version>
			dependency>

			
			<dependency>
				<groupId>com.fasterxml.jackson.coregroupId>
				<artifactId>jackson-databindartifactId>
				<version>${jackson.version}version>
			dependency>

			
			<dependency>
				<groupId>com.alibabagroupId>
				<artifactId>druidartifactId>
				<version>${druid.version}version>
			dependency>

			
			<dependency>
				<groupId>org.apache.httpcomponentsgroupId>
				<artifactId>httpclientartifactId>
				<version>${httpclient.version}version>
			dependency>

			
			<dependency>
				<groupId>jstlgroupId>
				<artifactId>jstlartifactId>
				<version>${jstl.version}version>
			dependency>
			<dependency>
				<groupId>javax.servletgroupId>
				<artifactId>servlet-apiartifactId>
				<version>${servlet-api.version}version>
				<scope>providedscope>
			dependency>
			<dependency>
				<groupId>javax.servletgroupId>
				<artifactId>jsp-apiartifactId>
				<version>${jsp-api.version}version>
				<scope>providedscope>
			dependency>

			
			<dependency>
				<groupId>joda-timegroupId>
				<artifactId>joda-timeartifactId>
				<version>${joda-time.version}version>
			dependency>

			
			<dependency>
				<groupId>org.apache.commonsgroupId>
				<artifactId>commons-lang3artifactId>
				<version>${commons-lang3.version}version>
			dependency>
			<dependency>
				<groupId>org.apache.commonsgroupId>
				<artifactId>commons-ioartifactId>
				<version>${commons-io.version}version>
			dependency>

		dependencies>
	dependencyManagement>

	<build>
		<finalName>${project.artifactId}finalName>
		<plugins>
			
			<plugin>
				<groupId>org.apache.maven.pluginsgroupId>
				<artifactId>maven-resources-pluginartifactId>
				<version>2.7version>
				<configuration>
					<encoding>UTF-8encoding>
				configuration>
			plugin>
			
			<plugin>
				<groupId>org.apache.maven.pluginsgroupId>
				<artifactId>maven-compiler-pluginartifactId>
				<version>3.2version>
				<configuration>
					<source>1.8source>
					<target>1.8target>
					<encoding>UTF-8encoding>
				configuration>
			plugin>
		plugins>
		<pluginManagement>
			<plugins>
				
				<plugin>
					<groupId>org.apache.tomcat.mavengroupId>
					<artifactId>tomcat7-maven-pluginartifactId>
					<version>2.2version>
				plugin>
			plugins>
		pluginManagement>
	build>


project>
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pom.xml(spring4)


<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>itcast-parentartifactId>
        <groupId>cn.itcast.parentgroupId>
        <version>0.0.1-SNAPSHOTversion>
    parent>
    <modelVersion>4.0.0modelVersion>
    <packaging>warpackaging>
    <artifactId>spring4artifactId>

    <properties>
        <maven.compiler.source>8maven.compiler.source>
        <maven.compiler.target>8maven.compiler.target>
    properties>
    <dependencies>
        
        <dependency>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-contextartifactId>
            <version>${spring.version}version>
        dependency>

        
        <dependency>
            <groupId>jstlgroupId>
            <artifactId>jstlartifactId>
            <version>${jstl.version}version>
        dependency>
        <dependency>
            <groupId>javax.servletgroupId>
            <artifactId>servlet-apiartifactId>
            <version>${servlet-api.version}version>
            <scope>providedscope>
        dependency>
        <dependency>
            <groupId>javax.servletgroupId>
            <artifactId>jsp-apiartifactId>
            <version>${jsp-api.version}version>
            <scope>providedscope>
        dependency>

        <dependency>
            <groupId>org.slf4jgroupId>
            <artifactId>slf4j-log4j12artifactId>
        dependency>

    dependencies>

    <build>
        <plugins>
            
            <plugin>
                <groupId>org.apache.tomcat.mavengroupId>
                <artifactId>tomcat7-maven-pluginartifactId>
                <version>2.2version>
                <configuration>
                    
                    <port>8088port>
                    
                    <path>/path>
                configuration>
            plugin>
        plugins>

    build>

project>
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用maven启动Tomcat

在这里插入图片描述

访问

http://localhost:8088/helloservlet

在这里插入图片描述

Spring的web集成 (Spring监听器)

【思考、阅读】直接new ClassPathXmlApplicationContext()有什么缺点？
缺点：
在创建Spring容器同时，需要对容器中对象初始化。而每次初始化容器的时候，都创建了新的容器对象，消耗了资源，降低了性能。
解决思路：保证容器对象只有一个。
解决方案：将Spring容器绑定到Web Servlet容器上，让Web容器来管理Spring容器的创建和销毁。
分析：
ServletContext在Web服务运行过程中是唯一的，其初始化的时候，会自动执行ServletContextListener 监听器（用来监听上下文的创建和销毁），具体步骤为：
编写一个ServletContextListener监听器，在监听ServletContext到创建的时候，创建Spring容器，并将其放到ServletContext的属性中保存（setAttribute(Spring容器名字，Spring容器对象) ）。
我们无需手动创建该监听器，因为Spring提供了一个叫ContextLoaderListener的监听器，它位于spring-web-4.3.13.RELEASE.jar中。

开发步骤：

第一步：引入spring-web的依赖

pom.xml(spring4)

        <dependency>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-webartifactId>
            <version>4.3.13.RELEASEversion>
        dependency>
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第二步：在web.xml 配置Spring的核心监听器

web.xml


<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">
    <servlet>
        <servlet-name>HelloServletservlet-name>
        <servlet-class>cn.itcast.spring.servlet.HelloServletservlet-class>
    servlet>
    <servlet-mapping>
        <servlet-name>HelloServletservlet-name>
        <url-pattern>/helloservleturl-pattern>
    servlet-mapping>
    
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListenerlistener-class>
    listener>
    
    <context-param>
        <param-name>contextConfigLocationparam-name>
        
        <param-value>classpath:applicationContext.xmlparam-value>
    context-param>

web-app>
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第三步：启动tomcat服务器，结果发现异常，因为默认会加载

在这里插入图片描述
根据异常提示：发现spring的BeanFactory没有初始化，说明没有找到spring容器，即applicationContext.xml文件

第四步：在web容器中配置spring文件路径

为什么没有找到applicationContext.xml文件呢？因为此时加载的是WEB-INF/applicationContext.xml，而不是src下的applicationContext.xml文件

原因：找到ContextLoaderListener.class，再找到ContextLoader.class，发现默认加载的WEB-INF/applicationContext.xml

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解决方案：
需要在web.xml中配置，加载spring容器applicationContext.xml文件的路径

web.xml

  
  <listener>
  	<listener-class>org.springframework.web.context.ContextLoaderListenerlistener-class>
  listener>
  
  <context-param>
  	<param-name>contextConfigLocationparam-name>
  	
  	<param-value>classpath:applicationContext.xmlparam-value>
  context-param>
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重新启动tomcat服务器，没有异常，问题解决。

第五步：修改Servlet代码。在Servlet 中通过ServletContext 获取Spring容器对象

第一种方式：使用getAttribute

//每次获取的都是一个spring容器
ApplicationContext applicationContext = 
(ApplicationContext)this.getServletContext().getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);
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第二种方式：使用WebApplicationContextUtils （推荐）

//工具类
WebApplicationContext applicationContext = WebApplicationContextUtils.getWebApplicationContext(this.getServletContext());
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HelloServlet.java

package cn.itcast.spring.servlet;

import cn.itcast.spring.service.HelloService;
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.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class HelloServlet extends HttpServlet {

    @Override
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        //1.传统方式：
        //new service
        //HelloService helloService = new HelloService();
        //spring方式：只要看到new，你就想到spring容器中的
        //ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");

        //2.每次获取的都是一个spring容器
       // ApplicationContext applicationContext = (ApplicationContext)this.getServletContext().getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);

        //3.工具类
        WebApplicationContext applicationContext = WebApplicationContextUtils.getWebApplicationContext(this.getServletContext());

        HelloService helloService=(HelloService)applicationContext.getBean("helloService");
        System.out.println("helloService = " + helloService);
        helloService.sayHello();
    }

    @Override
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        this.doGet(request, response);
    }

}

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在这里插入图片描述

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原文地址：https://blog.csdn.net/djydjy3333/article/details/126853419