spring属性配置执行过程，单列和原型区别

　　Spring配置中，采用属性注入时，当创建IOC容器时，也直接创建对象，并且执行相对应的setter方法

Student.java

package com.scope;

public class Student {
    private String name;
    private String number;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
        System.out.println(name);
    }
    public String getNumber() {
        return number;
    }
    public void setNumber(String number) {
        this.number = number;
    }
    public Student() {
        super();
        System.out.println("hello Student!");
        
    }
    
    
}

Main.java

package com.scope;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {
    public static void main(String[] args) {
        ApplicationContext ctx = new ClassPathXmlApplicationContext("beans-scope.xml");
        
    }
}

beans-scope.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="student1" class="com.scope.Student">
        <property name="name" value="Mary"></property>
        <property name="number" value="1120143231"></property>
    </bean>
    <bean id="student2" class="com.scope.Student">
        <property name="name" value="Curry"></property>
        <property name="number" value="1120111413"></property>
    </bean>
    
</beans>

执行结果

当创建IOC容器时，配置文件中有多少个bean就会创建多少个对象，并且执行相对应的setter函数。

我们对Main.java进行修改

package com.scope;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {
    public static void main(String[] args) {
        ApplicationContext ctx = new ClassPathXmlApplicationContext("beans-scope.xml");
        Student student1 = (Student) ctx.getBean("student1");
        Student student2 = (Student) ctx.getBean("student1");
        System.out.println(student1 == student2);
    }
}

执行结果：

当执行Student student1 = (Student) ctx.getBean("student1")时，并没有创建对象，只是创建了一个索引而已，Student1和Student2引用的是同一个对象。

以上就是单例模式，属性注入时，默认的就是单例模式，每个bean id只会创建一个对象，并且在创建IOC容器时，就创建对象和执行相对应的setter函数。

下面讲原型模式，即prototype模式。

Main.java

package com.scope;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {
    public static void main(String[] args) {
        ApplicationContext ctx = new ClassPathXmlApplicationContext("beans-scope.xml");
//        Student student1 = (Student) ctx.getBean("student1");
//        Student student2 = (Student) ctx.getBean("student1");
//        System.out.println(student1 == student2);
    }
}

beans-scope.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="student1" class="com.scope.Student" scope="prototype">
        <property name="name" value="Mary"></property>
        <property name="number" value="1120143231"></property>
    </bean>
    <bean id="student2" class="com.scope.Student" scope="prototype">
        <property name="name" value="Curry"></property>
        <property name="number" value="1120111413"></property>
    </bean>
    
</beans>

执行结果

采用prototype模式时，在创建IOC容器时，并没有创建相应的对象。我们继续对Main.java进行修改。

package com.scope;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {
    public static void main(String[] args) {
        ApplicationContext ctx = new ClassPathXmlApplicationContext("beans-scope.xml");
        Student student1 = (Student) ctx.getBean("student1");
        Student student2 = (Student) ctx.getBean("student1");
        System.out.println(student1 == student2);
    }
}

执行结果

在执行Student student1 = (Student) ctx.getBean("student1"); Student student2 = (Student) ctx.getBean("student1");创建了两个对象，所以输出了false。

采用prototype模式时，只有在获取bean时，才开始创建对象，获取多少次就创建多少个对象。