spring4.x依賴注入方法(DI)

1.DI方法

屬性注入(Setter方法注入)
構造器注入
工廠方法注入（很少使用，不推薦）

2.屬性注入(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;
    }

}

調用方法Main.java

package cn.com.pojo;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {

    public static void main(String[] args) {

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

        //2. 從 IOC 容器中獲取 bean 的實例
        OutputHelper outputHelper = (OutputHelper) ctx.getBean("OutputHelper");

        //根據類型來獲取 bean 的實例: 要求在  IOC 容器中只有一個與之類型匹配的 bean, 若有多個則會拋出異常. 
        //一般情況下, 該方法可用, 因爲一般情況下, 在一個 IOC 容器中一個類型對應的 bean 也只有一個. 
        //      OutputHelper outputHelper = ctx.getBean(OutputHelper.class);

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

3.構造器注入
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">
    <!-- 應該爲構造函數指定的確切數據類型-->
        <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;
    }

}

運行類：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工廠方法注入（很少使用，不推薦）