您的位置：首页 > 编程语言 > Java开发

通过实例解析spring bean之间的关系

2020-03-11 17:51 701 查看

这篇文章主要介绍了通过实例解析spring bean之间的关系,文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下

两种关系：继承、依赖

一、继承关系

Address.java

package com.gong.spring.beans.autowire;

public class Address {
private String city;
private String street;

public String getCity() {
return city;
}

public void setCity(String city) {
this.city = city;
}

public String getStreet() {
return street;
}

public void setStreet(String street) {
this.street = street;
}

@Override
public String toString() {
return "Address [city=" + city + ", street=" + street + "]";
}
}

beans-relation.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"
xmlns:p="http://www.springframework.org/schema/p"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
<bean id="address" class="com.gong.spring.beans.autowire.Address"
p:city="武汉" p:street="络南街道"></bean>
<!-- 使用parent指定指定哪个bean的配置，子bean可以覆盖父bean的配置 -->
<bean id="address2" class="com.gong.spring.beans.autowire.Address" parent="address"
p:street="珞狮街道"></bean>
</beans>

Main.java

package com.gong.spring.beans.autowire;

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("beans-relation.xml");
//2.从容器中获取Bean实例
Address address = (Address) ctx.getBean("address");
System.out.println(address.toString());Address address2 = (Address) ctx.getBean("address2");
System.out.println(address2.toString());
}
}

输出：

address2继承了address的city配置，因此city=武汉。

当然，我们也可以使用abstract来表明一个Bean是一个抽象bean。抽象bean可以作为一个模板，且不能被实例化。同时，如果一个bean没有声明class，那么该bean也是一个抽象bean，且必须指定abstract="true"。

<bean id="address" class="com.gong.spring.beans.autowire.Address" abstract="true"
p:city="武汉" p:street="络南街道"></bean>

此时，在进行实例化就会报错

Address address = (Address) ctx.getBean("address");

将抽象bean作为父bean，可以实例化它的子bean：

Address address2 = (Address) ctx.getBean("address2");
System.out.println(address2.toString());

二、依赖关系

Car.java

package com.gong.spring.beans.autowire;

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.autowire;
import java.util.List;
import java.util.Map;

public class Student {

private String name;
private int age;
private double score;
private Car car;
private Address address;
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 Car getCar() {
return car;
}
public void setCar(Car car) {
this.car = car;
}
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}
@Override
public String toString() {
return "Student [name=" + name + ", age=" + age + ", score=" + score + ", car=" + car + ", address=" + address
+ "]";
}

}

beans-relation.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"
xmlns:p="http://www.springframework.org/schema/p"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

<bean id="car" class="com.gong.spring.beans.autowire.Car" p:name="baoma"></bean>
<bean id="address" class="com.gong.spring.beans.autowire.Address"
p:city="武汉" p:street="络南街道"></bean>
<!-- 要求配置Student时，要依赖于Car-->
<bean id="student" class="com.gong.spring.beans.autowire.Student" p:name="tom"
p:age="12" p:score="99.00" autowire="byName" depends-on="car"></bean>
</beans>

spring允许用户通过depends-on属性设定bean前置依赖bean，前置依赖bean会在本Bean实例化之前就创建好。如果前置依赖于多个Bean，则可以通过逗号，空格的方式来配置bean的名称。

Main.java

package com.gong.spring.beans.autowire;

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("beans-relation.xml");
//2.从容器中获取Bean实例
Student student = (Student) ctx.getBean("student");
System.out.println(student.toString());
}
}

输出：

以上就是本文的全部内容，希望对大家的学习有所帮助

您可能感兴趣的文章:

内容来自用户分享和网络整理，不保证内容的准确性，如有侵权内容，可联系管理员处理

标签： spring bean 关系

相关文章推荐

新的分享

章节导航