Spring - Spring配置文件-Bean依赖注入详解

Bean的依赖注入分析

案例举例service层

编写UserService接口

package com.taotao.service;

/**
 * create by 刘鸿涛
 * 2022/4/5 17:53
 */
public interface UserService {
    public void save();
}

编写接口实现类UserServiceImpl

package com.taotao.service.impl;

import com.taotao.dao.UserDao;
import com.taotao.service.UserService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * create by 刘鸿涛
 * 2022/4/5 17:55
 */
public class UserServiceImpl implements UserService {

    public void save() {
        ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");

        //向下转型为UserDao类型
        UserDao userDao = (UserDao) app.getBean("userDao");
        userDao.save();
    }
}

模拟web层

编写UserController类

package com.taotao.demo;

import com.taotao.service.impl.UserServiceImpl;

/**
 * create by 刘鸿涛
 * 2022/4/5 17:59
 */
public class UserController {
    public static void main(String[] args) {
        UserServiceImpl userService = new UserServiceImpl();
        userService.save();
    }
}

测试运行

使用Spring.xml完成上面的案例

编写UserController类

package com.taotao.demo;

import com.taotao.service.UserService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * create by 刘鸿涛
 * 2022/4/5 17:59
 */
public class UserController {
    public static void main(String[] args) {
         ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserService userService = (UserService) app.getBean("userService");
        userService.save();
    }
}

编写Spring.xml

把userService配到容器中

<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.taotao.dao.impl.UserDaoImpl">bean>
    <bean id="userService" class="com.taotao.service.impl.UserServiceImpl">bean>
beans>

测试运行

分析

1. 目前UserService实例和UserDao实例都存在与Spring容器中，当前的做法是在容器外部获得UserService实例和UserDao实例，然后在程序中进行结合。

2. 因为UserService和UserDao都在Spring容器中，而最终程序直接使用的是UserService，所以可以在Spring容器中,将UserDao设置到UserService内部。

Bean的依赖注入概念

依赖注入(Dependency Injection)：他是Spring框架核心IOC的具体实现

在编写程序时，通过控制反转，把对象的创建交给了Spring，但是代码中不可能出现没有依赖的情况。IOC解耦只是降低他们的依赖关系，但不会消除。例如:业务层仍会调用持久层的方法。

那这种业务层和持久局的依赖关系，在使用Spring之后，就让Spring来维护了。简单的说，就是坐等框架把持久层对象传入业务层，而不用我们自己去获取。

如何将UserDao注入到UserService内部呢？

• 构造方法
• set方法

演示set方法注入

编写UserServiceImpl.java

package com.taotao.service.impl;

import com.taotao.dao.UserDao;
import com.taotao.service.UserService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * create by 刘鸿涛
 * 2022/4/5 17:55
 */
public class UserServiceImpl implements UserService {
    private UserDao userDao;

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

    public void save() {
//        ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
//
//        //向下转型为UserDao类型
//        UserDao userDao = (UserDao) app.getBean("userDao");
        userDao.save();
    }
}

编写spring.xml

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

测试运行

set注入扩展

p命名空间注入

P命名空间注入本质也是set方法注入，但比起上述的set方法注入更加方便，主要体现在配置文件中，如下:首先，需要引入P命名空间:

xmlns:p="http://www.springframework.org/schema/p"

其次，需要修改注入方法

<bean id="userService" class="com.taotao.service.impl.UserServiceImpl" p:userDao-ref="userDao"/>

演示构造方法注入

先把刚才的set方法注释掉

生成构造器，编写Service

package com.taotao.service.impl;

import com.taotao.dao.UserDao;
import com.taotao.service.UserService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * create by 刘鸿涛
 * 2022/4/5 17:55
 */
public class UserServiceImpl implements UserService {
    private UserDao userDao;

    public UserServiceImpl(UserDao userDao) {
        this.userDao = userDao;
    }

    public UserServiceImpl() {
        
    }

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

    public void save() {
//        ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
//
//        //向下转型为UserDao类型
//        UserDao userDao = (UserDao) app.getBean("userDao");
        userDao.save();
    }
}

编写Spring.xml

<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.taotao.dao.impl.UserDaoImpl">bean>
    <bean id="userService" class="com.taotao.service.impl.UserServiceImpl">
        <constructor-arg name="userDao" ref="userDao">constructor-arg>
    bean>
beans>

运行测试

Bean的依赖注入的数据类型

上面的操作，都是注入的引用Bean，除了对象的引河以注入，普通数据类型，集合等都可以在容器中进行注入。

注入数据的三种数据类型

• 普通数据类型
• 引用数据类型
• 集合数据类型

演示注入"普通数据类型"

编写UserDaoImpl.java

package com.taotao.dao.impl;

import com.taotao.dao.UserDao;
/**
 * create by 刘鸿涛
 * 2022/4/3 22:36
 */
public class UserDaoImpl implements UserDao {
    private String username;
    private int age;

    public void setUsername(String username) {
        this.username = username;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public void save() {
        System.out.println(username + "\n" + age );
        System.out.println("save running...");
    }
}

编写Spring.xml

<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.taotao.dao.impl.UserDaoImpl">
        <property name="username" value="taotao"/>
        <property name="age" value="18"/>
    bean>

    <bean id="userService" class="com.taotao.service.impl.UserServiceImpl">
        <constructor-arg name="userDao" ref="userDao">constructor-arg>
    bean>

beans>

测试运行

演示注入"集合类型"

编写UserDaoImpl.java

package com.taotao.dao.impl;

import com.taotao.dao.UserDao;
import com.taotao.domain.User;

import java.util.List;
import java.util.Map;
import java.util.Properties;

/**
 * create by 刘鸿涛
 * 2022/4/3 22:36
 */
public class UserDaoImpl implements UserDao {
    private String username;
    private int age;

    private List<String> strList;
    private Map<String, User> userMap;
    private Properties properties;

    public void setStrList(List<String> strList) {
        this.strList = strList;
    }

    public void setUserMap(Map<String, User> userMap) {
        this.userMap = userMap;
    }

    public void setProperties(Properties properties) {
        this.properties = properties;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public void save() {
        System.out.println(strList);
        System.out.println(userMap);
        System.out.println(properties);
        System.out.println("save running...");
    }
}

创建User.java

package com.taotao.domain;

/**
 * create by 刘鸿涛
 * 2022/4/5 22:06
 */
public class User {
    private String name;
    private String addr;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAddr() {
        return addr;
    }

    public void setAddr(String addr) {
        this.addr = addr;
    }

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", addr='" + addr + '\'' +
                '}';
    }
}

编写Spring.xml（注入List）

<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.taotao.dao.impl.UserDaoImpl">
        <property name="strList" >
            <list>
                <value>111value>
                <value>222value>
                <value>333value>
            list>
        property>
    bean>

    <bean id="userService" class="com.taotao.service.impl.UserServiceImpl">
        <constructor-arg name="userDao" ref="userDao">constructor-arg>
    bean>

beans>

运行测试

Spring.xml（注入Map）

<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.taotao.dao.impl.UserDaoImpl">
        <property name="strList" >
            <list>
                <value>111value>
                <value>222value>
                <value>333value>
            list>

        property>
        <property name="userMap">
            <map>
                <entry key="u1" value-ref="user1">entry>
                <entry key="u2" value-ref="user2">entry>
            map>
        property>
    bean>


    <bean id="user1" class="com.taotao.domain.User">
        <property name="name" value="tom"/>
        <property name="addr" value="beijing"/>
    bean>

    <bean id="user2" class="com.taotao.domain.User">
        <property name="name" value="jack"/>
        <property name="addr" value="shanghai"/>
    bean>

    <bean id="userService" class="com.taotao.service.impl.UserServiceImpl">
        <constructor-arg name="userDao" ref="userDao">constructor-arg>
    bean>

beans>

运行测试

Spring.xml（注入Properties）

<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.taotao.dao.impl.UserDaoImpl">
        <property name="strList" >
            <list>
                <value>111value>
                <value>222value>
                <value>333value>
            list>

        property>
        <property name="userMap">
            <map>
                <entry key="u1" value-ref="user1">entry>
                <entry key="u2" value-ref="user2">entry>
            map>

        property>

        <property name="properties">
            <props>
                <prop key="p1">pp1prop>
                <prop key="p2">pp2prop>
                <prop key="p3">pp3prop>
            props>
        property>
    bean>


    <bean id="user1" class="com.taotao.domain.User">
        <property name="name" value="tom"/>
        <property name="addr" value="beijing"/>
    bean>

    <bean id="user2" class="com.taotao.domain.User">
        <property name="name" value="jack"/>
        <property name="addr" value="shanghai"/>
    bean>

    <bean id="userService" class="com.taotao.service.impl.UserServiceImpl">
        <constructor-arg name="userDao" ref="userDao">constructor-arg>
    bean>



beans>

运行测试