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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