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：
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