Spring依赖注入的三种方法

妖狐艹你老母 2023-03-13 15:30 18阅读 0赞

Spring 管理java bean主要以依赖注入(控制反转IOC)的方式进行管理。其中有三种方式：属性注入、构造函数、工厂方法(非静态和静态，主要是以方法是否静态进行注入)

People类：

package com.xiaowu.entity;
    
    public class People {
    	int id;
    	String name;
    	int age;
    	
    	
    	
    	public People() {
    		super();
    		// TODO Auto-generated constructor stub
    	}
    	public People(int id, String name, int age) {
    		super();
    		this.id = id;
    		this.name = name;
    		this.age = age;
    	}
    	public int getId() {
    		return id;
    	}
    	public void setId(int id) {
    		this.id = id;
    	}
    	public String getName() {
    		return name;
    	}
    	public void setName(String name) {
    		this.name = name;
    	}
    	public int getAge() {
    		return age;
    	}
    	public void setAge(int age) {
    		this.age = age;
    	}
    	@Override
    	public String toString() {
    		return "People [id=" + id + ", name=" + name + ", age=" + age + "]";
    	}
    	
    }

1，属性注入：

beans.xml：

<?xml version="1.0" encoding="UTF-8"?>
    <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="people" class="com.xiaowu.entity.People">
    	</bean>
      
      	<bean id="people1" class="com.xiaowu.entity.People">
    	  	<property name="id" value="01"></property>
    	  	<property name="name" value="小一"></property>
    	  	<property name="age" value="11"></property>
    	</bean>
    	
    	
    </beans>

main方法控制台输出：

package com.xiaowu.test;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import com.xiaowu.entity.People;
    
    public class Test2 {
    	public static void main(String[] args) {
    		ApplicationContext ac = new ClassPathXmlApplicationContext("beans.xml");
    		
    
    		// 属性注入
    		People people1 = (People) ac.getBean("people1");
    
    		
    		System.out.println(people1.toString());
    	}
    }

2，构造函数注入；(通过类型；通过索引；联合使用) :

1)类型：

beans.xml

<?xml version="1.0" encoding="UTF-8"?>
    <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="people" class="com.xiaowu.entity.People">
    	</bean>
      
    	<bean id="people2" class="com.xiaowu.entity.People">
    		<constructor-arg type="int" value="22"></constructor-arg>
    		<constructor-arg type="String" value="小2"></constructor-arg>
    		<constructor-arg type="int" value="22"></constructor-arg>
    	</bean>
    	
    	
    </beans>

main方法控制台输出：

package com.xiaowu.test;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import com.xiaowu.entity.People;
    
    public class Test2 {
    	public static void main(String[] args) {
    		ApplicationContext ac = new ClassPathXmlApplicationContext("beans.xml");
    		
    
    		// 属性注入
    		People people1 = (People) ac.getBean("people2");
    
    		
    		System.out.println(people2.toString());
    	}
    }

2) 通过索引

beans.xml:

<?xml version="1.0" encoding="UTF-8"?>
    <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="people3" class="com.xiaowu.entity.People">
    		<constructor-arg index="0" value="33"></constructor-arg>
    		<constructor-arg index="1" value="小三"></constructor-arg>
    		<constructor-arg index="2" value="33"></constructor-arg>
    	</bean>
    
    </beans>

控制台输出：

package com.xiaowu.test;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import com.xiaowu.entity.People;
    
    public class Test2 {
    	public static void main(String[] args) {
    		ApplicationContext ac = new ClassPathXmlApplicationContext("beans.xml");
    		
    
    		// 属性注入
    		People people3 = (People) ac.getBean("people3");
    
    		
    		System.out.println(people3.toString());
    	}
    }

3) 联合使用

就是在bean标签内中的加index='0"或者type="int"

beans.xml

<?xml version="1.0" encoding="UTF-8"?>
    <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="people4" class="com.xiaowu.entity.People">
    		<constructor-arg type="int" value="44"></constructor-arg>
    		<constructor-arg index="1" value="小四"></constructor-arg>
    		<constructor-arg index="2" value="44"></constructor-arg>
    	</bean>
    	
    </beans>

main方法控制台输出：

package com.xiaowu.test;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import com.xiaowu.entity.People;
    
    public class Test2 {
    	public static void main(String[] args) {
    		ApplicationContext ac = new ClassPathXmlApplicationContext("beans.xml");
    		
    
    		// 属性注入
    		People people4 = (People) ac.getBean("people4");
    
    		
    		System.out.println(people4.toString());
    	}
    }

3，工厂方法注入；(非静态工厂，静态工厂)

非静态工厂：

1)首先创建工厂类：

package com.xiaowu.factory;
    
    import com.xiaowu.entity.People;
    
    public class PeopleFactory {
    	public People crteatePeople() {
    		People people = new People();
    		people.setId(55);
    		people.setName("xiaowu");
    		people.setAge(55);
    		return people;
    	}
    }

注意：该工厂类中的方法是非静态的 ，必须实例化工厂类（factory-bean）后才能调用工厂方法。

beans.xml:

<?xml version="1.0" encoding="UTF-8"?>
    <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="peopleFactory" class="com.xiaowu.factory.PeopleFactory"></bean>
    	<bean id="people5" factory-bean="peopleFactory" factory-method="crteatePeople"></bean>
    	
    </beans>

在上面的xml配置文件中 <bean id="peopleFactory" class="com.xiaowu.factory.PeopleFactory"></bean> 先创建工厂类bean ,在创建People类的bean 加入factory-bean="peopleFactory" 和 factory-method="crteatePeople" 然后在控制台输出：

package com.xiaowu.test;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import com.xiaowu.entity.People;
    
    public class Test2 {
    	public static void main(String[] args) {
    		ApplicationContext ac = new ClassPathXmlApplicationContext("beans.xml");
    		
    
    		// 属性注入
    		People people5 = (People) ac.getBean("people5");
    
    		
    		System.out.println(people5.toString());
    	}
    }

非静态工厂：

1) 创建静态工厂类

package com.xiaowu.factory;
    
    import com.xiaowu.entity.People;
    
    public static class PeopleFactory {
    	public People crteatePeople() {
    		People people = new People();
    		people.setId(55);
    		people.setName("xiaowu");
    		people.setAge(55);
    		return people;
    	}
    }

beans.xml:

该类中的方法是静态的 所以不需要创建该类的bean 直接使用该类的静态方法即可。

main方法控制台输出：

package com.xiaowu.test;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import com.xiaowu.entity.People;
    
    public class Test2 {
    	public static void main(String[] args) {
    		ApplicationContext ac = new ClassPathXmlApplicationContext("beans.xml");
    		
    
    		// 属性注入
    		People people6 = (People) ac.getBean("people6");
    
    		
    		System.out.println(people6.toString());
    	}
    }