1. Bean的依赖注入概念

依赖注入（Dependency Injection）：它是 Spring 框架外围 IOC 的具体实现。在编写程序时，通过管制反转，把对象的创立交给了 Spring，然而代码中不可能呈现没有依赖的状况。IOC 解耦只是升高他们的依赖关系，但不会打消。例如：业务层仍会调用长久层的办法。那这种业务层和长久层的依赖关系，在应用 Spring 之后，就让 Spring 来保护了。简略的说，就是坐等框架把长久层对象传入业务层，而不必咱们本人去获取。

2. Bean的依赖注入形式

（1）set办法

在UserServiceImpl中增加setUserDao办法

public class UserServiceImpl implements UserService {    private UserDao userDao;    public void setUserDao(UserDao userDao) {        this.userDao = userDao;          }     @Override        public void save() {                  userDao.save();    }}
<bean id="userDao" class="com.wange.dao.impl.UserDaoImpl"/><bean id="userService" class="com.wange.service.impl.UserServiceImpl">    <property name="userDao" ref="userDao"></property></bean>

（2）构造方法

创立有参结构

public class UserServiceImpl implements UserService {        @Override    public void save() {        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");               UserDao userDao = (UserDao) applicationContext.getBean("userDao");        userDao.save();    }}
<bean id="userDao" class="com.wange.dao.impl.UserDaoImpl"/><bean id="userService" class="com.wange.service.impl.UserServiceImpl">                     <constructor-arg name="userDao" ref="userDao"></constructor-arg></bean>

3. Bean的依赖注入的数据类型

注入数据的三种数据类型

一般数据类型
援用数据类型
汇合数据类型

Bean的依赖注入的数据类型

（1）一般数据类型的注入

package com.wange.dao.impl;import com.wange.dao.UserDao;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+"----"+age);        System.out.println("save办法正在执行");    }}
<bean id="userDao" class="com.wange.dao.impl.UserDaoImpl">    <property name="username" value="lisi"></property>    <property name="age" value="20"></property></bean>
package com.wange.test;import com.wange.dao.UserDao;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;//测试public class UserController {    public static void main(String[] args) {            ApplicationContext applicationContext =                    new ClassPathXmlApplicationContext("applicationContext.xml");            UserDao userDao = (UserDao) applicationContext.getBean("userDao");            userDao.save();    }}

（2）汇合数据类型（List）String 的注入

package com.wange.dao.impl;import com.wange.dao.UserDao;import com.wange.domain.User;import java.util.List;public class UserDaoImpl implements UserDao{    private List<String> stringList;    public void setStringList(List<String> stringList) {        this.stringList = stringList;    }    public void save() {        System.out.println(stringList);        System.out.println("save办法正在执行");    }}
<bean id="userDao" class="com.wange.dao.impl.UserDaoImpl">    <property name="stringList">        <list>            <value>str1</value>            <value>str2</value>            <value>str3</value>        </list>    </property></bean>

（3）汇合数据类型（List）User 的注入

package com.wange.dao.impl;import com.wange.dao.UserDao;import com.wange.domain.User;import java.util.List;public class UserDaoImpl implements UserDao {    private List<User> userList;    public void setUserList(List<User> userList) {    this.userList = userList;   }public void save() {    System.out.println(userList);    System.out.println("save办法正在执行");    }}
<bean id="user1" class="com.wange.domain.User"/><bean id="user2" class="com.wange.domain.User"/><bean id="userDao" class="com.wange.dao.impl.UserDaoImpl">    <property name="userList">        <list>            <bean class="com.wange.domain.User"/>            <bean class="com.wange.domain.User"/>            <ref bean="user1"/>            <ref bean="user2"/>               </list>    </property></bean>

4）汇合数据类型（ Map<String,User> ）的注入

package com.wange.dao.impl;import com.wange.dao.UserDao;import com.wange.domain.User;import java.util.List;import java.util.Map;import java.util.Properties;public class UserDaoImpl implements UserDao{    private Map<String, User> userMap;    public void setUserMap(Map<String, User> userMap) {        this.userMap = userMap;    }    public void save() {        System.out.println(userMap);        System.out.println("save办法正在执行");    }}
<bean id="user1" class="com.wange.domain.User"/><bean id="user2" class="com.wange.domain.User"/><bean id="userDao" class="com.wange.dao.impl.UserDaoImpl">    <property name="userMap">        <map>                        <entry key="u1" value-ref="user1"/>            <entry key="u2" value-ref="user2"/>        </map>    </property></bean>

（5）汇合数据类型（Properties）的注入

package com.wange.dao.impl;import com.wange.dao.UserDao;import java.util.Properties;public class UserDaoImpl implements UserDao{    private Properties properties;    public void setProperties(Properties properties) {        this.properties = properties;    }    public void save() {        System.out.println(properties);        System.out.println("save办法正在执行");    }}
<bean id="userDao" class="com.wange.dao.impl.UserDaoImpl">      <property name="properties">            <props>                <prop key="p1">properties1</prop>                <prop key="p2">properties2</prop>                <prop key="p3">properties3</prop>            </props>      </property>  </bean>
package com.wange.test;import com.wange.dao.UserDao;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;//测试public class UserController {    public static void main(String[] args) {            ApplicationContext applicationContext =                    new ClassPathXmlApplicationContext("applicationContext.xml");            UserDao userDao = (UserDao) applicationContext.getBean("userDao");            userDao.save();    }}

运行后果

最初

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