Spring入门（2）-通过构造器注入Bean

Spring入门（2）-通过构造器注入Bean

前一篇文章将了最基本的spring例子，这篇文章中，介绍一下带有参数的构造函数和通过构造器注入对象引用。

0. 目录

1. 带有参数的构造函数
2. 通过构造器注入对象引用
3. 通过工厂方法创建Bean

1. 带有参数的构造函数

把需要实例化的类中增加一个有参数的构造函数

package com.chzhao.springtest;

public class PersonBll implements IPersonBll {

	private Person person;

	public PersonBll() {

	}

	public PersonBll(String name) {
		this.person = new Person();
		this.person.setName(name);
	}

	public void show() {
		if (this.person != null) {
			System.out.println(this.person.getName());
		} else {
			System.out.println("no person");
		}
	}

	public void addPerson(Person p) {
		System.out.println("add person: " + p.getName());
	}
}

配置文件

<?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  name="PersonBll" class="com.chzhao.springtest.PersonBll">
		<constructor-arg value="老王"></constructor-arg>
	</bean>
</beans>

通过这种方式，可以把参数传入到构造函数中。

2. 通过构造器注入对象引用

把构造函数改为引用类型，代码如下：

package com.chzhao.springtest;

public class PersonBll implements IPersonBll {

	private Person person;

	public Person getPerson() {
		return person;
	}

	public void setPerson(Person person) {
		this.person = person;
	}

	public PersonBll() {

	}

	public PersonBll(Person p) {
		this.person = p;
	}

	public void show() {
		if (this.person != null) {
			System.out.println(this.person.getName());
		} else {
			System.out.println("no person");
		}
	}

	public void addPerson(Person p) {
		System.out.println("add person: " + p.getName());
	}
}

同时配置文件改为

<?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 name="laowang" class="com.chzhao.springtest.Person">
		<property name="name" value="老王" />
	</bean>
	<bean  name="PersonBll" class="com.chzhao.springtest.PersonBll">
		<constructor-arg ref="laowang"></constructor-arg>
	</bean>
</beans>

3. 通过工厂方法创建Bean

有时候一些对象是通过工厂方法实例化的，这里介绍一下。

package com.chzhao.springtest;

public class BllFactory {

	public static PersonBll getPersonBll() {
		Person p = new Person();
		p.setName("老李");
		PersonBll bll = new PersonBll(p);
		return bll;
	}
}

对应配置文件

<?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  name="PersonBll" class="com.chzhao.springtest.BllFactory"
     factory-method="getPersonBll">
	</bean>
</beans>