spring

简介: spring
  • spring简介
  • spring ioc容器的特点
  • spring注入方式
  • spring上下文与tomcat整合

1.spring简介

1. 什么是spring,它能够做什么?

  Spring是一个开源框架,它由Rod Johnson创建。它是为了解决企业应用开发的复杂性而创建的。

  Spring使用基本的JavaBean来完成以前只可能由EJB完成的事情。

  然而,Spring的用途不仅限于服务器端的开发。从简单性、可测试性和松耦合的角度而言,任何Java应用都可以从Spring中受益。

  目的:解决企业应用开发的复杂性

  功能:使用基本的JavaBean代替EJB,并提供了更多的企业应用功能

  范围:任何Java应用

  简单来说,Spring是一个轻量级的控制反转(IoC)和面向切面(AOP)的容器框架。

2.spring ioc容器的特点

2. 什么是控制反转(或依赖注入)

  控制反转(IoC=Inversion of Control)IoC,用白话来讲,就是由容器控制程序之间的(依赖)关系,而非传统实现中,由程序代码直接操控。这也就是所谓“控制反转”的概念所在:(依赖)控制权由应用代码中转到了外部容器,控制权的转移,是所谓反转。

  IoC还有一个另外的名字:“依赖注入 (DI=Dependency Injection)”  ,即由容器动态的将某种依赖关系注入到组件之中

  案例:实现Spring的IoC


  IOC/DI

    将以前由程序员实例化对象/赋值的工作交给了spring处理

//pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<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>ideamaven</artifactId>
        <groupId>org.example</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>
    <artifactId>Spring</artifactId>
    <packaging>war</packaging>
    <name>Spring Maven Webapp</name>
    <!-- FIXME change it to the project's website -->
    <url>http://www.example.com</url>
    <properties>
        <spring.version>5.0.1.RELEASE</spring.version>
        <javax.servlet.version>4.0.0</javax.servlet.version>
        <junit.version>4.12</junit.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>3.8.1</version>
            <scope>test</scope>
        </dependency>
        <!-- 2、导入spring依赖 -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-aspects</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <!-- 5.1、junit -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>${junit.version}</version>
            <scope>test</scope>
        </dependency>
        <!-- 5.2、servlet -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>${javax.servlet.version}</version>
            <scope>provided</scope>
        </dependency>
    </dependencies>
    <build>
        <finalName>Spring</finalName>
        <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
            <plugins>
                <plugin>
                    <artifactId>maven-clean-plugin</artifactId>
                    <version>3.1.0</version>
                </plugin>
                <!-- see http://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_war_packaging -->
                <plugin>
                    <artifactId>maven-resources-plugin</artifactId>
                    <version>3.0.2</version>
                </plugin>
                <plugin>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>3.8.0</version>
                </plugin>
                <plugin>
                    <artifactId>maven-surefire-plugin</artifactId>
                    <version>2.22.1</version>
                </plugin>
                <plugin>
                    <artifactId>maven-war-plugin</artifactId>
                    <version>3.2.2</version>
                </plugin>
                <plugin>
                    <artifactId>maven-install-plugin</artifactId>
                    <version>2.5.2</version>
                </plugin>
                <plugin>
                    <artifactId>maven-deploy-plugin</artifactId>
                    <version>2.8.2</version>
                </plugin>
            </plugins>
        </pluginManagement>
    </build>
</project>

package com.zlj.ioc.service;
/**
 * @author zlj
 * @create 2023-08-15 16:46
 */
public interface UserService {
    public void update();
}
package com.zlj.ioc.service;
/**
 * @author zlj
 * @create 2023-08-15 16:46
 *
 * 客户的需求:
 * 需求:客户登陆后需要具备更改个人信息的功能
 *
 * 场景1:
 * 客户要求,在新增的需求上做迭代版本,如头像上传
 *
 * 场景2:
 * 客户需求,在新增的需求上做优化,提升性能,如多线程
 *
 *
 *
 */
public class UserServiceImp implements UserService{
public void update(){
    System.out.println("更改个人用户信息");
//    添加上传头像的功能代码
//    System.out.println("上传头像功能");
}
}
package com.zlj.ioc.service;
/**
 * @author zlj
 * @create 2023-08-15 16:56
 */
public class UserServiceImp2 implements UserService{
    public void update(){
        System.out.println("更改个人用户信息");
//    添加上传头像的功能代码
    System.out.println("上传头像功能");
    }
}
package com.zlj.ioc.web;
import com.zlj.ioc.service.UserService;
/**
 * @author zlj
 * @create 2023-08-15 21:20
 */
public class GoodsAction {
    private UserService userservice;
    public UserService getUserservice() {
        return userservice;
    }
    public void setUserservice(UserService userservice) {
        this.userservice = userservice;
    }
    public String update(){
        userservice.update();
        return "list";
    }
}
package com.zlj.ioc.web;
import com.zlj.ioc.service.UserService;
/**
 * @author zlj
 * @create 2023-08-15 17:07
 * <p>
 * 程序员手动实例化对象的弊端
 * 1.一旦依的接口的实现需要大批量改动,迭代,维护的成本极高
 * 2.当接口的实现类不统一,维护成本更高
 */
public class UserAction {
    private UserService userservice;
    public UserService getUserservice() {
        return userservice;
    }
    public void setUserservice(UserService userservice) {
        this.userservice = userservice;
    }
    public String update() {
        userservice.update();
        return "list";
    }
}
<?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">
<!--凡是在sprng配置文件spring-context.xml中配置,那么该类javabean就交给了spring容器管理-->
    <bean class="com.zlj.ioc.web.UserAction" id="userAction">
        <property name="userservice" ref="userservice"></property>
    </bean>
    <bean class="com.zlj.ioc.web.GoodsAction" id="goodsAction">
        <property name="userservice" ref="UserServiceImp"></property>
    </bean>
    <bean class="com.zlj.ioc.service.UserServiceImp2" id="userservice"></bean>
    <bean class="com.zlj.ioc.service.UserServiceImp" id="UserServiceImp"></bean>
</beans>
package com.zlj.ioc.demo;
import com.zlj.ioc.web.GoodsAction;
import com.zlj.ioc.web.UserAction;
import org.springframework.context.support.ClassPathXmlApplicationContext;
/**
 * @author zlj
 * @create 2023-08-15 22:26
 */
public class demo1 {
    public static void main(String[] args) {
        //加载spring核心配置文件(建模),获取spring的上下文对象,上下文对象中可以获取任何Javabean对象
        ClassPathXmlApplicationContext context=new ClassPathXmlApplicationContext("/spring-context.xml");
        UserAction userAction= (UserAction) context.getBean("userAction");
        userAction.update();
        GoodsAction goodsAction = (GoodsAction) context.getBean("goodsAction");
        goodsAction.update();
    }
}

3.spring注入方式

1.第一种注入方式( set方法属性注入,GoodsAction):

package com.zlj.ioc.web;
import com.zlj.ioc.service.UserService;
import java.util.List;
/**
 * @author zlj
 * @create 2023-08-15 21:20
 * spring的注入方式
 * 
 */
public class GoodsAction {
    private UserService userservice;
    private String gname;
    private int age;//保质期
    private List<String> people;//商品的使用人群
    public List<String> getPeople() {
        return people;
    }
    public void setPeople(List<String> people) {
        this.people = people;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public String getGname() {
        return gname;
    }
    public void setGname(String gname) {
        this.gname = gname;
    }
    public UserService getUserservice() {
        return userservice;
    }
    public void setUserservice(UserService userservice) {
        this.userservice = userservice;
    }
    public String update(){
        userservice.update();
        return "list";
    }
    public void pros(){
        System.out.println(this.gname);
        System.out.println(this.age);
        System.out.println(this.people);
    }
}
<?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">
<!--凡是在sprng配置文件spring-context.xml中配置,那么该类javabean就交给了spring容器管理-->
    <bean class="com.zlj.ioc.web.UserAction" id="userAction">
        <property name="userservice" ref="userservice"></property>
    </bean>
    <bean class="com.zlj.ioc.web.GoodsAction" id="goodsAction">
        <property name="userservice" ref="UserServiceImp"></property>
        <property name="gname" value="鱼"></property>
        <property name="age" value="1"></property>
        <property name="people">
            <list>
                <value>比目鱼</value>
                <value>金鱼</value>
            </list>
        </property>
    </bean>
    <bean class="com.zlj.ioc.service.UserServiceImp2" id="userservice"></bean>
    <bean class="com.zlj.ioc.service.UserServiceImp" id="UserServiceImp"></bean>
</beans>

2.第二种注入方式(构造注入,UserAction):

package com.zlj.ioc.web;
import com.zlj.ioc.service.UserService;
import java.util.List;
/**
 * @author zlj
 * @create 2023-08-15 17:07
 * <p>
 * 程序员手动实例化对象的弊端
 * 1.一旦依的接口的实现需要大批量改动,迭代,维护的成本极高
 * 2.当接口的实现类不统一,维护成本更高
 */
public class UserAction {
    private UserService userservice;
    private String uname;
    private int age;
    private List<String> hobby;
    public UserAction() {
    }
    public UserAction(String uname, int age, List<String> hobby) {
        this.uname = uname;
        this.age = age;
        this.hobby = hobby;
    }
    public List<String> getHobby() {
        return hobby;
    }
    public void setHobby(List<String> hobby) {
        this.hobby = hobby;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public String getUname() {
        return uname;
    }
    public void setUname(String uname) {
        this.uname = uname;
    }
    public UserService getUserservice() {
        return userservice;
    }
    public void setUserservice(UserService userservice) {
        this.userservice = userservice;
    }
    public String update() {
        userservice.update();
        return "list";
    }
    public void pros(){
        System.out.println(this.uname);
        System.out.println(this.age);
        System.out.println(this.hobby);
    }
}
<?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">
<!--凡是在sprng配置文件spring-context.xml中配置,那么该类javabean就交给了spring容器管理-->
    <bean class="com.zlj.ioc.web.UserAction" id="userAction">
        <property name="userservice" ref="userservice"></property>
        <constructor-arg name="uname" value="小白"></constructor-arg>
        <constructor-arg name="age" value="18"></constructor-arg>
        <constructor-arg name="hobby">
            <list>
                <value>哈士奇</value>
                <value>狸花猫</value>
                <value>猎犬</value>
            </list>
        </constructor-arg>
    </bean>
    <bean class="com.zlj.ioc.web.GoodsAction" id="goodsAction">
        <property name="userservice" ref="UserServiceImp"></property>
        <property name="gname" value="鱼"></property>
        <property name="age" value="1"></property>
        <property name="people">
            <list>
                <value>比目鱼</value>
                <value>金鱼</value>
            </list>
        </property>
    </bean>
    <bean class="com.zlj.ioc.service.UserServiceImp2" id="userservice"></bean>
    <bean class="com.zlj.ioc.service.UserServiceImp" id="UserServiceImp"></bean>
</beans>
package com.zlj.ioc.demo;
import com.zlj.ioc.web.GoodsAction;
import com.zlj.ioc.web.UserAction;
import org.springframework.context.support.ClassPathXmlApplicationContext;
/**
 * @author zlj
 * @create 2023-08-15 22:26
 */
public class demo1 {
    public static void main(String[] args) {
        //加载spring核心配置文件(建模),获取spring的上下文对象,上下文对象中可以获取任何Javabean对象
        ClassPathXmlApplicationContext context=new ClassPathXmlApplicationContext("/spring-context.xml");
        UserAction userAction= (UserAction) context.getBean("userAction");
        userAction.update();
        System.out.println("=================================================================");
        userAction.pros();
        GoodsAction goodsAction = (GoodsAction) context.getBean("goodsAction");
        goodsAction.update();
        System.out.println("===============================================================");
        goodsAction.pros();
    }
}

3.第三种引用方式(自动装配中的byName和byType):

byName:JavaBean会根据属性名在spring是根据spring上下文中进行查找

是根据spring上下文中的bean的id进行查,只要有,就会自动注入

byType:JavaBean会根据属性名对应的接口类型,在spring上下文中进行查找

是根据spring上下文中是否有该接口类型的实现类进行匹配,只要有,就会自动注入

注意:如果找到两个及以上,那么spring会报错

//byName
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       default-autowire="byName"
       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">
<!--凡是在sprng配置文件spring-context.xml中配置,那么该类javabean就交给了spring容器管理-->
    <bean class="com.zlj.ioc.web.UserAction" id="userAction">
<!--        <property name="userservice" ref="userservice"></property>-->
<!--        <constructor-arg name="uname" value="小白"></constructor-arg>-->
<!--        <constructor-arg name="age" value="18"></constructor-arg>-->
<!--        <constructor-arg name="hobby">-->
<!--            <list>-->
<!--                <value>哈士奇</value>-->
<!--                <value>狸花猫</value>-->
<!--                <value>猎犬</value>-->
<!--            </list>-->
<!--        </constructor-arg>-->
    </bean>
    <bean class="com.zlj.ioc.web.GoodsAction" id="goodsAction">
<!--        <property name="userservice" ref="UserServiceImp"></property>-->
<!--        <property name="gname" value="鱼"></property>-->
<!--        <property name="age" value="1"></property>-->
<!--        <property name="people">-->
<!--            <list>-->
<!--                <value>比目鱼</value>-->
<!--                <value>金鱼</value>-->
<!--            </list>-->
<!--        </property>-->
    </bean>
    <bean class="com.zlj.ioc.service.UserServiceImp2" id="userservice"></bean>
    <bean class="com.zlj.ioc.service.UserServiceImp" id="UserServiceImp"></bean>
</beans>
//byType
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       default-autowire="byType"
       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">
<!--凡是在sprng配置文件spring-context.xml中配置,那么该类javabean就交给了spring容器管理-->
    <bean class="com.zlj.ioc.web.UserAction" id="userAction">
<!--        <property name="userservice" ref="userservice"></property>-->
<!--        <constructor-arg name="uname" value="小白"></constructor-arg>-->
<!--        <constructor-arg name="age" value="18"></constructor-arg>-->
<!--        <constructor-arg name="hobby">-->
<!--            <list>-->
<!--                <value>哈士奇</value>-->
<!--                <value>狸花猫</value>-->
<!--                <value>猎犬</value>-->
<!--            </list>-->
<!--        </constructor-arg>-->
    </bean>
    <bean class="com.zlj.ioc.web.GoodsAction" id="goodsAction">
<!--        <property name="userservice" ref="UserServiceImp"></property>-->
<!--        <property name="gname" value="鱼"></property>-->
<!--        <property name="age" value="1"></property>-->
<!--        <property name="people">-->
<!--            <list>-->
<!--                <value>比目鱼</value>-->
<!--                <value>金鱼</value>-->
<!--            </list>-->
<!--        </property>-->
    </bean>
<!--    <bean class="com.zlj.ioc.service.UserServiceImp2" id="userservice"></bean>-->
    <bean class="com.zlj.ioc.service.UserServiceImp" id="UserServiceImp"></bean>
</beans>

4.spring上下文与tomcat整合(监听器)

package com.king.ioc.listener;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;
/**
 * @author zlj
 * @create 2023-08-16 3:05
 */
@WebListener
public class StringLoadListener implements ServletContextListener {
    @Override
    public void contextInitialized(ServletContextEvent sce) {
        System.out.println("初始化:将spring上下文放入tomcat上下文");
//       将spring上下文放入tomcat上下文
        ClassPathXmlApplicationContext context=new ClassPathXmlApplicationContext("/spring-context.xml");
//        获取comcat上下文
        ServletContext servletContext = sce.getServletContext();
        servletContext.setAttribute("springContext",context);
    }
}
package com.zlj.ioc.web;
import com.zlj.ioc.service.UserService;
import org.springframework.context.support.ClassPathXmlApplicationContext;
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;
/**
 * @author zlj
 * @create 2023-08-16 3:14
 */
@WebServlet("/userList")
public class UserServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req, resp);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //加载spring核心配置文件(建模),获取spring的上下文对象,上下文对象中可以获取任何Javabean对象
        ClassPathXmlApplicationContext context=new ClassPathXmlApplicationContext("/spring-context.xml");
        UserService userserivce = (UserService) context.getBean("userservice");
        System.out.println(userserivce);
        userserivce.update();
    }
}

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