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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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