spring之配置单例的集合bean，以供多个bean进行引用

Posted 2021-03-18 西西嘛呦

<?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:util="http://www.springframework.org/schema/util"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.3.xsd">
    
    <bean id="car1" class="com.gong.spring.beans.Car">
        <property name="name" value="baoma"></property>
    </bean>
    <bean id="car2" class="com.gong.spring.beans.Car">
        <property name="name" value="benchi"></property>
    </bean>
    <bean id="car3" class="com.gong.spring.beans.Car">
        <property name="name" value="binli"></property>
    </bean>
    
    <bean id="student" class="com.gong.spring.beans.Student">
        <property name="name" value="tom"></property>
        <property name="age" value="12"></property>
        <property name="score" value="98.00"></property>
        <property name="cars">
            <!-- 使用List节点为List集合属性赋值 
            <list>
                <ref bean="car1"/>
                <ref bean="car2"/>
                <ref bean="car3"/>
            </list>
        </property>
        
    </bean>

</beans>

这种情况下，是在一个bean的里面进行配置的，假设现在我们有另外一个bean，也需要使用List集合里的bean，那么应该怎么做呢？

首先，引入命名空间util，在applicationContext.xml下方的namespace里面，勾选下即可。如果没有，则需要安装Spring Tool Suite(STS) for Eclipse，具体装法可百度。

然后配置一个公用集合bean：

    <util:list id="cars">
        <ref bean="car1"/>
        <ref bean="car2"/>
        <ref bean="car3"/>
    </util:list>

此时可去掉上述代码中的红色部分，并这样使用：

<property name="cars" ref="cars">

补充其它代码：

Car.java

package com.gong.spring.beans;

public class Car {
    
    public Car() {
    }

    public Car(String name) {
        this.name = name;
    }
    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "Car [name=" + name + "]";
    }
    
}

Student.java

package com.gong.spring.beans;
import java.util.List;
import java.util.Map;

public class Student {
    
    private String name;
    private int age;
    private double score;
    private List<Car> cars;
    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;
    }
    public double getScore() {
        return score;
    }
    public void setScore(double score) {
        this.score = score;
    }
    public List<Car> getCars() {
        return cars;
    }
    public void setCars(List<Car> cars) {
        this.cars = cars;
    }
    @Override
    public String toString() {
        return "Student [name=" + name + ", age=" + age + ", score=" + score + ", cars=" + cars + "]";
    }
    
    
}

Main.java

package com.gong.spring.beans;

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

public class Main {
    public static void main(String[] args) {
        //1.创建spring的IOC容器对象
        ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
        //2.从容器中获取Bean实例
        Student student = (Student) ctx.getBean("student"); 
        System.out.println(student.toString());
    }
}

输出：

 

顺便看一下util中都有什么：

 

对于不同的集合，按照其相应的语法进行配置即可。