Spring 依赖注入 (构造函数注入、Setter注入 、嵌套注入、 文件方式注入)

依赖注入方式

-基于构造函数

public class ScrewDriver{
	private Header header;
	public ScrewDriver(Header header){
		this.header = header;
	}
}

-基于Setter方法

public class ScrewDriver{
	private Header header;
	public setDriver(Header header){
		this.header = header;
	}
}

实际开发选择

强依赖 → 构造函数

可选依赖 → Setter方法 （可配置）

通过构造函数依赖注入

• 定义接口

package cn.test.controller;

public interface Header {
    public void doWord();
    public String getInfo();
}

• 接口实现

package cn.test.controller;

public class StraightHeader implements Header {

    private String color;
    private int size;

    public StraightHeader(){}

    public StraightHeader(String color, int size) {
        this.color = color;
        this.size = size;
    }

    @Override
    public void doWord() {
        System.out.println("doWord");
    }

    @Override
    public String getInfo() {
      return "StraightHeader"+color+"--- SIZE:"+size;
    }
}

• 实例测试

package cn.test.controller;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
@RequestMapping("/cren")
public class TestContainer {
    @RequestMapping("/test")
    public static void main(String [] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        Header header = context.getBean("header", StraightHeader.class);
        System.out.println(header.getInfo());
        header.doWord();
    }

}

• Bean注入

 <bean id="header" class="cn.test.controller.StraightHeader">
        <constructor-arg value="red"></constructor-arg>
        <constructor-arg value="15"></constructor-arg>
    </bean>

通过构造函数依赖注入 （集合）

• 定义接口

package cn.test.controller;

public interface Header {
    public void doWord();
    public String getInfo();
}

• 接口实现

package cn.test.controller;

public class StraightHeader implements Header {

    private String color;
    private int size;

    public StraightHeader(){}

    public StraightHeader(String color, int size) {
        this.color = color;
        this.size = size;
    }
	//改
    public StraightHeader(Map<String,String> paras){
        this.color = paras.get("color");
        this.size =Integer.valueOf(paras.get("size"));
    }

    @Override
    public void doWord() {
        System.out.println("doWord");
    }

    @Override
    public String getInfo() {
      return "StraightHeader"+color+"--- SIZE:"+size;
    }
}

• 实例测试

package cn.test.controller;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
@RequestMapping("/cren")
public class TestContainer {
    @RequestMapping("/test")
    public static void main(String [] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        Header header = context.getBean("header", StraightHeader.class);
        System.out.println(header.getInfo());
        header.doWord();
    }

}

• Bean注入

//改
<bean id="header" class="cn.test.controller.StraightHeader">
        <constructor-arg>
            <map>
                <entry key="color" value="red"></entry>
                <entry key="size" value="12"></entry>
            </map>
        </constructor-arg>
    </bean>

文件方式注入Bean

<bean id="header" class="cn.test.controller.StraightHeader">
    <constructor-arg name="color" value="${color}"> </constructor-arg>
    <constructor-arg name="size" value="${size}"> </constructor-arg>
 </bean>
//加入以下配置
 <bean id = "headerProperties"
          class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="location" value="classpath:header.properties"></property>
    </bean>

//建立文件header.properties，参数写入即可

嵌套注入

<bean id="screwDriver" class="cn.test.controller.ScrewDriver">
    <constructor-arg >
    	<ref bean="header">
    </constructor-arg>
 </bean>
 
 <bean id="header" class="cn.test.controller.StraightHeader">
        <constructor-arg value="red"></constructor-arg>
        <constructor-arg value="15"></constructor-arg>
    </bean>

通过Setter依赖注入

• 定义接口

package cn.test.controller;

public interface Header {
    public void doWord();
    public String getInfo();
}

• 接口实现

package cn.test.controller;

public class StraightHeader implements Header {

    private String color;
    private int size;

    public StraightHeader(){}

    public StraightHeader(String color, int size) {
        this.color = color;
        this.size = size;
    }
	
	//改
	public void setColor(String color){
		this.color=color;
	}
	public void setSize(String size){
		this.size=size;
	}
    @Override
    public void doWord() {
        System.out.println("doWord");
    }

    @Override
    public String getInfo() {
      return "StraightHeader"+color+"--- SIZE:"+size;
    }
}

• 实例测试

package cn.test.controller;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
@RequestMapping("/cren")
public class TestContainer {
    @RequestMapping("/test")
    public static void main(String [] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        Header header = context.getBean("header", StraightHeader.class);
        System.out.println(header.getInfo());
        header.doWord();
    }

}

• Bean注入

 <bean id="header" class="cn.test.controller.StraightHeader">
        <property name="color" value="${color}"></constructor-arg>
        <preperty name="size" value="${size}"></constructor-arg>
    </bean>

构造函数注入和Setter注入两者的区别 ：

构造函数注入，必须将定义的构造函数所有参数注入设值，而Setter不用，他可以只设值一个值或者多个值，一般来说如果构造注入的值是固定的建议用构造函数注入，如果不固定用Setter注入