Spring框架依赖注入 Spring框架依赖注入方法示例
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在阅读这篇文章之前，大家可以先参阅《理解Spring中的依赖注入和控制反转》一文，了解下依赖注入和控制反转的相关内容。
三种依赖注入的方式
属性注入，通过setter方法注入bean的属性值或依赖的对象 构造注入 工厂方法注入（很少使用）
例子
这里我们使用了spring-4.3.2，maven配置文件
<dependency>
<groupid>org.springframework</groupid>
spring-core</artifactid>
<version>${org.springframework-version}</version>
<exclusions>
<exclusion>
<groupid>commons-logging</groupid>
commons-logging</artifactid>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupid>org.springframework</groupid>
spring-beans</artifactid>
<version>${org.springframework-version}</version>
</dependency>
<dependency>
<groupid>org.springframework</groupid>
spring-aop</artifactid>
<version>${org.springframework-version}</version>
</dependency>
<dependency>
<groupid>org.springframework</groupid>
spring-context</artifactid>
<version>${org.springframework-version}</version>
</dependency>
<dependency>
<groupid>commons-logging</groupid>
commons-logging</artifactid>
<version>1.2</version>
</dependency>
<!-- Junit -->
<dependency>
<groupid>junit</groupid>
junit</artifactid>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
applicationContext.xml配置文件
<!--?xml version="1.0" encoding="UTF-8"?-->
<beans xmlns="https://www.springframework.org/schema/beans" xmlns:p="https://www.springframework.org/schema/p" xmlns:util="https://www.springframework.org/schema/util" xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance" xsi:schemalocation="https://www.springframework.org/schema/beans https://www.springframework.org/schema/beans/spring-beans.xsd
https://www.springframework.org/schema/util https://www.springframework.org/schema/util/spring-util.xsd">
<!--
配置bean
id：标识容器中bean对象
class：bean的全类名，通过反射的方式在IOC容器中创建Bean，所以要求Bean类必须有无参构造器
-->
<bean class="com.spring.test.HelloWorld" id="helloWorld">
<property name="name" value="crystal"></property>
</bean>
<!-- 通过构造方法配置bean,可以指定参数的位置和类型，以区分重载的构造函数 -->
<bean class="com.spring.test.Car" id="car">
<constructor-arg index="0" value="BENCHI"></constructor-arg>
<constructor-arg index="1" type="double" value="200000.0"></constructor-arg>
</bean>
<bean class="com.spring.test.Car" id="car1">
<!-- 如果字面值包含特殊字符，使用<![CDATA[]]>包裹起来
属性值可以使用value子节点来配置
-->
<constructor-arg type="java.lang.String">
<value><!--[CDATA[<shanghai-->]]></value>
</constructor-arg>
<constructor-arg index="1" type="int" value="200"></constructor-arg>
</bean>
<bean class="com.spring.test.Person" id="person">
<property name="name" value="Crystal"></property>
<property name="age" value="20"></property>
<!-- 可以使用ref建立引用之间的关系 -->
<!--
<property name="car" ref="car"></property>
-->
<!--
<property name="car">
<ref bean="car2"/>
</property>
-->
<!--
<property name="car">
<bean class="com.spring.test.Car">
<constructor-arg value="changanFute"></constructor-arg>
<constructor-arg value="3000000"></constructor-arg>
<constructor-arg value="240"></constructor-arg>
</bean>
</property>
-->
<!-- 测试赋值null -->
<!-- <property name="car"><null/></property> -->
<property name="car" ref="car1"></property>
<!-- 为级联属性赋值，注意：属性需要先初始化后才能为级联属性赋值，和structs2不同 -->
<property name="car.price" value="400000"></property>
</bean>
<!-- 测试配置集合属性 -->
<bean class="com.spring.test.collections.Person" id="person3">
<property name="name" value="barry"></property>
<property name="age" value="21"></property>
<property name="cars">
<list>
<ref bean="car">
<ref bean="car1">
<bean class="com.spring.test.Car">
<constructor-arg value="changanFute"></constructor-arg>
<constructor-arg value="3000000"></constructor-arg>
<constructor-arg value="240"></constructor-arg>
</bean>
</ref></ref></list>
</property>
</bean>
<!-- 配置Map的属性值 -->
<bean class="com.spring.test.collections.NewPerson" id="newPerson">
<property name="name" value="lina"></property>
<property name="age" value="22"></property>
<property name="cars">
<!-- 使用map节点及map的entry子节点配置Map类型的成员变量 --><map>
<entry key="AA" value-ref="car"></entry>
<entry key="BB" value-ref="car1"></entry></map>
</property>
</bean>
<!-- 配置Properties属性值 -->
<bean class="com.spring.test.collections.DataSource" id="dataSource">
<property name="properties">
<!-- 使用props和prop子节点来为Properties属性赋值 -->
<props>
<prop key="user">root</prop>
<prop key="password">1234</prop>
<prop key="jdbcUrl">jdbc:mysql://test</prop>
<prop key="jdbcDriver">com.mysql.jdbc.Driver</prop>
</props>
</property>
</bean>
<!-- 配置单例的集合bean，以供多个bean进行引用，需要导入util命名空间 -->
<util:list id="cars">
<ref bean="car">
<ref bean="car1">
</ref></ref></util:list>
<bean class="com.spring.test.collections.Person" id="person4">
<property name="name" value="Jackie"></property>
<property name="age" value="30"></property>
<property name="cars" ref="cars"></property>
</bean>
<!-- 通过p命名空间为bean的属性赋值，需要先导入p命名空间，相对于传统配置方式更为简洁 -->
<bean class="com.spring.test.collections.Person" id="person5" p:age="32" p:cars-ref="cars" p:name="Queue"></bean>
</beans>
1. 下面是简单的属性注入、构造注入的测试类
Car.java
package com.spring.test;
public class Car {
private String name;
private int maxSpeed;
private double price;
public Car() {
}
public Car(String name, double price) {
this.name = name;
this.price = price;
}
public Car(String name, int maxSpeed) {
this.name = name;
this.maxSpeed = maxSpeed;
}
public Car(String name, double price, int maxSpeed) {
this.name = name;
this.price = price;
this.maxSpeed = maxSpeed;
}
public void setPrice(double price) {
this.price = price;
}
@Override
public String toString() {
return "Car [name:" + name + ", price:" + price + ", maxSpeed:" + maxSpeed + "]";
}
}
HelloWorld.java
package com.spring.test;
public class HelloWorld {
private String name;
public HelloWorld() {
System.out.println("HelloWorld constructor...");
}
public String getName() {
return name;
}
public void setName(String name) {
System.out.println("setName:" + name);
this.name = name;
}
@Override
public String toString() {
return "hello," + name;
}
}
Person.java
package com.spring.test;
public class Person {
private String name;
private int age;
private Car car;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public Car getCar() {
return car;
}
public void setCar(Car car) {
this.car = car;
}
@Override
public String toString() {
return "Person: [name=" + name + ", age=" + age + ", car=" + car + "]";
}
}
Main.java
package com.spring.test;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class Main {
public static void main(String[] args) {
HelloWorld hello = new HelloWorld();
hello.setName("barry");
System.out.println("print:"+ hello + "\n");
// 装入 Spring 配置文件
/**
* 装入 Spring 配置文件
* ApplicationContext是IOC容器，它有两个主要实现类（ClassPathXmlApplicationContext和FileSystemXmlApplicationContext）
* ApplicationContext在初始化上下文时就实例化所有单例的Bean
*/
ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
//HelloWorld hello1 = (HelloWorld) context.getBean("helloWorld"); // 通过id获取bean对象
HelloWorld hello1 = context.getBean(HelloWorld.class);
// 通过类型获取bean对象（要求在IOC容器里该类型的对象只能有一个）
System.out.println(hello1);
}
@Test
public void testContructor() {
ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
Car car = (Car) context.getBean("car");
// 通过类型获取bean对象（要求在IOC容器里该类型的对象只能有一个）
Car car1 = (Car) context.getBean("car1");
System.out.println(car);
System.out.println(car1);
Person person = (Person) context.getBean("person");
System.out.println(person);
}
}
2. 下面是集合的测试类
NewPerson.java
package com.spring.test.collections;
import java.util.Map;
import com.spring.test.Car;
public class NewPerson {
private String name;
private int age;
private Map<string, car=""> cars;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public Map<string, car=""> getCars() {
return cars;
}
public void setCars(Map<string, car=""> cars) {
this.cars = cars;
}
@Override
public String toString() {
return "Person: [name=" + name + ", age=" + age + ", cars=" + cars + "]";
}
}
Person.java
package com.spring.test.collections;
import java.util.List;
import com.spring.test.Car;
public class Person {
private String name;
private int age;
private List<car> cars;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public List<car> getCars() {
return cars;
}
public void setCars(List<car> cars) {
this.cars = cars;
}
@Override
public String toString() {
return "Person: [name=" + name + ", age=" + age + ", cars=" + cars + "]";
}
}
DataSource.java
package com.spring.test.collections;
import java.util.Properties;
public class DataSource {
private Properties properties;
public Properties getProperties() {
return properties;
}
public void setProperties(Properties properties) {
this.properties = properties;
}
@Override
public String toString() {
return "DataSource: [properties:" + properties + "]";
}
}
Main.java
package com.spring.test.collections;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class Main {
@Test
public void testCollections() {
ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
Person person = (Person) context.getBean("person3");
System.out.println(person);
NewPerson newPerson = (NewPerson) context.getBean("newPerson");
System.out.println(newPerson);
DataSource dataSource = (DataSource) context.getBean("dataSource");
System.out.println(dataSource);
Person person4 = (Person) context.getBean("person4");
System.out.println(person4);
Person person5 = (Person) context.getBean("person5");
System.out.println(person5);
}
}
总结
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