spring的依赖注入DI详解编程语言

依赖注入的方式：
1.构造函数依赖注入
2.setter方法依赖注入

p名称空间的使用
Spring2.5 版本，引入p名称空间，作用简化 setter方法注入的配置
第一步：在xml配置文件中，配置p名称空间
xmlns:p = “http://www.springframework.org/schema/p”
第二步：通过p名称空间语法，简化setter方式属性注入
 p:<属性名>=”xxx” 引入常量值
 p:<属性名>-ref=”xxx” 引用其它Bean对象

<bean id="employee" class="cn.itcast.spring.e_di.Employee"> 
        <property name="name" value="小明"></property> 
        <!-- 复杂类型对象， 可以通过 ref 属性引用目标bean的id  --> 
        <property name="car" ref="car"></property> 
</bean> 
改造为  
<!-- p名称空间  --> 
    <bean id="employee2"  
class="cn.itcast.spring.e_di.Employee"  
p:name="小丽" p:car-ref="car"></bean>

2） SpEL 表达式使用
Spring Expression Language Spring表达式语言，从3.0版本开始提供
语法格式 #{..} 主要用于spring配置文件
引入对象，引用对象属性，引用对象方法

<!-- spEL 使用 --> 
    <bean id="mycar" class="cn.itcast.spring.e_di.Car2" p:carName="#{'qq'.toUpperCase()}"  
p:price="#{car2.price}"></bean> 
    <bean id="myemployee" class="cn.itcast.spring.e_di.Employee" p:name="老张" p:car="#{car}"></bean>

代码示例：
Car.java

package com.my.di; 
 
//轿车 （构造器 依赖注入） 
public class Car { 
 
    private String name; 
    private double price ; 
 
    // 在构造Car对象时，将name和price 属性注入car对象 
    public Car(String name, double price) { 
        super(); 
        this.name = name; 
        this.price = price; 
    } 
 
    @Override 
    public String toString() { 
        return "Car [name=" + name + ", price=" + price + "]"; 
    } 
 
}

Car2.java

package com.my.di; 
 
//轿车 通过setter方法完成属性注入 
public class Car2 { 
 
    private String name; 
    private double price ; 
 
    public String getName() { 
        return name; 
    } 
 
    public void setName(String name) { 
        this.name = name; 
    } 
 
    public double getPrice() { 
        return price; 
    } 
 
    public void setPrice(double price) { 
        this.price = price; 
    } 
 
    @Override 
    public String toString() { 
        return "Car [name=" + name + ", price=" + price + "]"; 
    } 
 
}

Employee.java

package com.my.di; 
 
public class Employee { 
 
    private Car car ; 
    private String name; 
 
    public void setCar(Car car) { 
        this.car = car; 
    } 
    public void setName(String name) { 
        this.name = name; 
    } 
 
    public Employee(Car car, String name) { 
        super(); 
        this.car = car; 
        this.name = name; 
    } 
 
    public Employee() { 
    } 
 
    @Override 
    public String toString() { 
        return "Employee [car=" + car + ", name=" + name + "]"; 
    }  
 
 
}

applicationContext.xml

?xml version="1.0" encoding="UTF-8"?> 
<beans xmlns="http://www.springframework.org/schema/beans" 
       xmlns:p = "http://www.springframework.org/schema/p" 
       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"> 
        <!--  属性依赖注入 --> 
    <!-- 构造器注入 --> 
    <bean id="car" class="com.my.di.Car"> 
        <!-- 构造函数中属性注入，使用 constructor-arg 标签完成注入 --> 
        <!-- 根据index 和 type 属性完成注入  --> 
        <constructor-arg index="0" type="java.lang.String" value="宝马"></constructor-arg> 
        <constructor-arg index="1" type="double" value="1000000"></constructor-arg> 
    </bean> 
 
    <!-- setter方法注入 --> 
    <bean id="car2" class="com.my.di.Car2"> 
        <!-- 一个属性 ，对应一个property 元素 --> 
        <property name="name" value="保时捷"></property> 
        <property name="price" value="1500000"></property> 
    </bean> 
 
    <bean id="employee" class="com.my.di.Employee"> 
        <property name="name" value="小明"></property> 
        <!-- 复杂类型对象， 可以通过 ref 属性引用目标bean的id  --> 
        <property name="car" ref="car"></property> 
    </bean> 
 
    <!-- p名称空间  spring2.5  --> 
    <bean id="employee2" class="com.my.di.Employee" p:name="小丽" p:car-ref="car"></bean> 
 
    <!-- spEL 使用 spring3.0--> 
    <bean id="mycar" class="com.my.di.Car2" p:name="#{'qq'.toUpperCase()}" p:price="#{car2.price}"></bean> 
    <bean id="myemployee" class="com.my.di.Employee" p:name="老张" p:car="#{car}"></bean> 
 
</beans>

Test.java

package com.my.di; 
 
import org.springframework.context.ApplicationContext; 
import org.springframework.context.support.ClassPathXmlApplicationContext; 
 
 
public class Test { 
 
    @org.junit.Test 
    // 测试构造函数注入 
    public void demo1(){ 
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml"); 
        Car car = (Car) applicationContext.getBean("car"); 
        System.out.println(car); 
    } 
 
    @org.junit.Test 
    // 测试setter方法注入 
    public void demo2(){ 
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml"); 
        Car2 car2 = (Car2) applicationContext.getBean("car2"); 
        System.out.println(car2); 
    } 
 
    @org.junit.Test 
    // 测试setter方法注入 (复杂属性) 
    public void demo3(){ 
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml"); 
        Employee employee = (Employee) applicationContext.getBean("employee"); 
        System.out.println(employee); 
    } 
 
    @org.junit.Test 
    // 测试setter方法注入 (p名称空间) 
    public void demo4(){ 
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml"); 
        Employee employee2 = (Employee) applicationContext.getBean("employee2"); 
        System.out.println(employee2); 
    } 
 
    @org.junit.Test 
    // 测试setter方法注入 (spEL使用) 
    public void demo5(){ 
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml"); 
        Car2 mycar = (Car2) applicationContext.getBean("mycar"); 
        System.out.println(mycar); 
        Employee employee = (Employee) applicationContext.getBean("myemployee"); 
        System.out.println(employee); 
    } 
 
}

运行结果：

这里写图片描述

集合属性的注入
Spring 提供集合对象注入四个标签 <list> <set> <map> <props>
代码示例：

CollectionBean.java

package com.my.collection; 
 
import java.util.List; 
import java.util.Map; 
import java.util.Properties; 
import java.util.Set; 
 
import com.my.di.Car; 
 
//注入 集合类型 属性  
public class CollectionBean { 
 
    private List<String> hobbies; 
    private List<Car> cars; 
    private Set<Integer> scores; 
    private Map<String, String> map; 
    private Properties properties; 
 
    public void setHobbies(List<String> hobbies) { 
        this.hobbies = hobbies; 
    } 
    public void setCars(List<Car> cars) { 
        this.cars = cars; 
    } 
    public void setScores(Set<Integer> scores) { 
        this.scores = scores; 
    } 
    @Override 
    public String toString() { 
        return "CollectionBean [ hobbies=" + hobbies + ",/n cars=" + cars 
                + ", scores=" + scores + ",/n map=" + map + ",/n properties=" 
                + properties + " ]"; 
    } 
 
    public void setMap(Map<String, String> map) { 
        this.map = map; 
    } 
    public void setProperties(Properties properties) { 
        this.properties = properties; 
    } 
 
 
}

applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?> 
<beans xmlns="http://www.springframework.org/schema/beans" 
       xmlns:p = "http://www.springframework.org/schema/p" 
       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"> 
    <!--  集合属性注入 --> 
    <bean id="collectionBean" class="com.my.collection.CollectionBean"> 
        <property name="hobbies"> 
            <list> 
                <value>音乐</value> 
                <value>体育</value> 
            </list> 
        </property> 
        <property name="cars"> 
            <list> 
                <ref bean="car"/> 
            </list> 
        </property> 
        <property name="scores"> 
            <set> 
                <value>100</value> 
                <value>90</value> 
            </set> 
        </property> 
        <property name="map"> 
            <map> 
                <entry key="公司" value="百度"></entry> 
                <entry key="人数" value="100"></entry> 
            </map> 
        </property> 
        <property name="properties"> 
            <props> 
                <prop key="城市">北京</prop> 
                <prop key="年龄">20</prop> 
            </props> 
        </property> 
    </bean> 
 
</beans>

Test.java

package com.my.collection; 
 
import org.springframework.context.ApplicationContext; 
import org.springframework.context.support.ClassPathXmlApplicationContext; 
 
 
public class Test { 
 
    @org.junit.Test 
    public void test() { 
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml"); 
        CollectionBean bean = (CollectionBean) applicationContext.getBean("collectionBean"); 
        System.out.println(bean); 
    } 
 
}

运行结果：
这里写图片描述

原创文章，作者：ItWorker，如若转载，请注明出处：https://blog.ytso.com/12102.html

spring的依赖注入DI详解编程语言

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