Spring IOC 四种依赖注入

Spring IOC 四种依赖注入

前期准备

• 1、创建一个Maven工程

• 2、创建一个实体类

  public class User {
  	private Integer id;
  	private String userName;
  	private String password;
  	private String note;
      
  	public User setId(Integer id) {
  		this.id = id;
  		return this;
  	}
  	public User setUserName(String userName) {
  		this.userName = userName;
  		return this;
  	}
  	public User setPassword(String password) {
  		this.password = password;
  		return this;
  	}
  	public User setNote(String note) {
  		this.note = note;
  		return this;
  	}
      //注意 ：toString,get方法自行实现，
  }
  

• 3、引入pom依赖

  <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context</artifactId>
      <version>4.1.1.RELEASE</version>
  </dependency>
  

• 4、在src/main/java中创建beans.xml，并写入如下内容

  <?xml version="1.0" encoding="UTF-8"?>
  <beans xmlns="http://www.springframework.org/schema/beans"
  	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  	xmlns:p="http://www.springframework.org/schema/p"
  	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd">
  
  </beans>
  

一、静态工厂

• 1、首先创建一个静态工厂UserFactory

  public class UserFactory {
  	private static User user;
  	public static User getInstance() {
  		if(user == null) {
  			user = new User();
  			user.setId(1).setUserName("王五").setPassword("hwy499").setNote("无");
  		}
  		return user;
  	}
  }
  

• 2、在Beans.xml文件中配置该静态工厂

  <?xml version="1.0" encoding="UTF-8"?>
  <beans xmlns="http://www.springframework.org/schema/beans"
  	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  	xmlns:p="http://www.springframework.org/schema/p"
  	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd">
     
      <!-- factory-method : 获得对象的静态方法名 class:静态工厂类的全限定类名-->
  	<bean class="com.factory.UserFactory" factory-method="getInstance"  id ="userFactory">
  	</bean>
  </beans>
  

• 3、测试

  public class UserFactoryTest {
  	public static void main(String[] args) {
  		// 加载 beans.xml
  		ClassPathXmlApplicationContext cpac = new 
  				ClassPathXmlApplicationContext("beans.xml");
          // 获得实例
  		User user = cpac.getBean("userFactory", User.class);
          // 打印
  		System.out.println(user); 
          //User [id=1, userName=王五, password=hwy499, note=无]
  	}
  }
  

二、实例工厂注入

• 1、创建一个工厂类UserFactory

  public class UserFactory {
  	private User user;
  	public User getInstance() {
  		if (user == null) {
  			user = new User();
  			user.setId(1).setUserName("王五").setPassword("hwy499").setNote("无");
  		}
  		return user;
  	}
  }
  

• 2、在beans.xml中配置工厂类的实例

  <?xml version="1.0" encoding="UTF-8"?>
  <beans xmlns="http://www.springframework.org/schema/beans"
  	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  	xmlns:p="http://www.springframework.org/schema/p"
  	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd">
  
  	<bean class="com.factory.UserFactory" id="userFactory">
  	</bean>
  	
  	<bean class="com.bean.User" factory-bean="userFactory"  factory-method="getInstance" id = "user">
  	</bean>
  </beans>
  

• 3、测试

  public class UserFactoryTest {
  	public static void main(String[] args) {
  		//加载 beans.xml
  		ClassPathXmlApplicationContext cpac = new 
  				ClassPathXmlApplicationContext("beans.xml");
  		//User user = cpac.getBean("userFactory", User.class);
  		User user = cpac.getBean("user",User.class);
  		System.out.println(user); 
           //User [id=1, userName=王五, password=hwy499, note=无]
  	}
  }
  

三、Set 方法注入

• 1、在beans.xml中进行如下配置

  <?xml version="1.0" encoding="UTF-8"?>
  <beans xmlns="http://www.springframework.org/schema/beans"
  	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  	xmlns:p="http://www.springframework.org/schema/p"
  	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd">
      <!--通过set方法注入 为什么这种方法叫做通过set方法注入呢？
  		这个跟我们在property标签中添加的name有关，在property中添加的name
  		并不是我们实体类中的属性名，而是我们在其中添加的set方法中set之后的名字，
  		假如我们现在实体类中有一个属性叫name，而它对应的set方法为setUserName,
  		那么我就要在property标签中添加name="username",而不是name="name"
  	-->
  	<bean id="user" class="com.bean.User">
  		<property name="id" value="1" />
  		<property name="userName" value="李四" />
  		<property name="password" value="123456123" />
  		<property name="note" value="我是一个备注" />
  	</bean>
  </beans>
  

• 2、测试

  public class SetTest {
  	public static void main(String[] args) {
  		//加载 beans.xml
  		ClassPathXmlApplicationContext cpac = new 
  				ClassPathXmlApplicationContext("beans.xml");
  		//User user = cpac.getBean("userFactory", User.class);
  		User user = cpac.getBean("user",User.class);
  		System.out.println(user); 
           //User [id=1, userName=王五, password=hwy499, note=无]
  	}
  }
  

四、通过构造方法注入

• 1、在实体类添加构造方法

  public User(){} //无参构造函数
  public User(Integer id, String userName, String password, String note) {
      super();
      this.id = id;
      this.userName = userName;
      this.password = password;
      this.note = note;
  }
  

• 2、在bens.xml中添加如下配置

  <?xml version="1.0" encoding="UTF-8"?>
  <beans xmlns="http://www.springframework.org/schema/beans"
  	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  	xmlns:p="http://www.springframework.org/schema/p"
  	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd">
  
  	<bean id="user" class="com.bean.User">
  		<constructor-arg name="id" value="1" />
  		<constructor-arg name="userName" value="李四" />
  		<constructor-arg name="password" value="123456" />
  		<constructor-arg name="note" value="无备注消息" />
  	</bean>
  	<!--或是-->
      <bean id="user1" class="com.bean.User">
  		<constructor-arg index="0" value="1" />
  		<constructor-arg index="1" value="李四" />
  		<constructor-arg index="2" value="123456" />
  		<constructor-arg index="3" value="无备注消息" />
  	</bean>
  	<!--在或是 此时要注意先后问题，此时是按照你的构造函数的参数顺序依次赋值-->
      <bean id="user2" class="com.bean.User">
  		<constructor-arg  value="1" />
  		<constructor-arg  value="李四" />
  		<constructor-arg  value="123456" />
  		<constructor-arg  value="无备注消息" />
  	</bean>
  </beans>
  

• 3、测试

  public class ConstructorTest {
  	public static void main(String[] args) {
  		//加载 beans.xml
  		ClassPathXmlApplicationContext cpac = new 
  				ClassPathXmlApplicationContext("beans.xml");
  		//User user = cpac.getBean("userFactory", User.class);
  		User user = cpac.getBean("user",User.class);
  		System.out.println(user); 
          // User [id=1, userName=李四, password=123456, note=无备注消息]
  	}
  }
  

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