通过实例解析spring bean之间的关系

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，也希望大家多多支持。