spring4.x依赖注入方法(DI)

1.DI方法

属性注入(Setter方法注入)

构造器注入

工厂方法注入（很少使用，不推荐）

2.属性注入(Setter方法注入)

applicationContext-bean.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:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd"> 
<bean id="OutputHelper" class="cn.com.pojo.OutputHelper">
<property name="outputGenerator">
<ref bean="CsvOutputGenerator" />
</property>
</bean>

<bean id="CsvOutputGenerator" class="cn.com.pojo.CsvOutputGenerator" />
<bean id="JsonOutputGenerator" class="cn.com.pojo.JsonOutputGenerator" />

</beans>

OutputHelper.java

package cn.com.pojo.output;

import com.yiibai.output.IOutputGenerator;

public class OutputHelper
{
IOutputGenerator outputGenerator;

public void setOutputGenerator(IOutputGenerator outputGenerator){
this.outputGenerator = outputGenerator;
}

}

调用方法Main.java

package cn.com.pojo;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {

public static void main(String[] args) {

//1. 创建 Spring 的 IOC 容器
ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext-bean.xml");

//2. 从 IOC 容器中获取 bean 的实例
OutputHelper outputHelper = (OutputHelper) ctx.getBean("OutputHelper");

//根据类型来获取 bean 的实例: 要求在  IOC 容器中只有一个与之类型匹配的 bean, 若有多个则会抛出异常.
//一般情况下, 该方法可用, 因为一般情况下, 在一个 IOC 容器中一个类型对应的 bean 也只有一个.
//      OutputHelper outputHelper = ctx.getBean(OutputHelper.class);

//3. 使用 bean
System.out.println(outputHelper)
}
}

3.构造器注入

applicationContext-bean..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:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd"> 
<bean id="CustomerBean" class="cn.com.pojo.Customer">
<!-- 应该为构造函数指定的确切数据类型-->
<constructor-arg type="java.lang.String">
<value>yiibai</value>
</constructor-arg>

<constructor-arg type="java.lang.String">
<value>188</value>
</constructor-arg>

<constructor-arg type="int">
<value>28</value>
</constructor-arg>

</bean>

</beans>

Customer.java

package cn.com.pojo;

public class Customer
{
private String name;
private String address;
private int age;

public Customer(String name, String address, int age) {
this.name = name;
this.address = address;
this.age = age;
}

public Customer(String name, int age, String address) {
this.name = name;
this.age = age;
this.address = address;
}
//getter and setter methods
public String toString(){
return " name : " +name + "\n address : "
+ address + "\n age : " + age;
}

}

运行类：App .java

package cn.com.pojo;

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

public class App
{
public static void main( String[] args )
{
ApplicationContext context =
new ClassPathXmlApplicationContext(new String[] {"Spring-Customer.xml"});

Customer cust = (Customer)context.getBean("CustomerBean");
System.out.println(cust);
// name : yiibai
// address : 28
// age : 188
}
}

4工厂方法注入（很少使用，不推荐）