IOC装配Bean
（1）Spring框架Bean实例化的方式提供了三种方式实例化Bean
下面先写这三种方法的applicationContext.xml配置文件：
<?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:p="http://www.springframework.org/schema/p" 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.xsd"> <!-- Bean的三种实例化方式=================== --> <!-- 2.1 使用无参的构造器 --> <bean id="bean1" class="com.study.spring.b_instance.Bean1"></bean> <!-- 2.2使用静态工厂方法 factory-method 是工厂提供的静态方法 --> <bean id="bean2" class="com.study.spring.b_instance.Bean2" factory-method="createInstance"></bean> <!-- 2.3配置实例化工厂的方法 --> <bean id="bean3Factory" class="com.study.spring.b_instance.Bean3Factory"></bean> <bean id="bean3" factory-bean="bean3Factory" factory-method="getInstance"></bean> <!-- end.Bean的三种实例化方式==================== -->
Bean1类
public class Bean1 { //必须提供无参的构造函数 系统有默认无参的构造函数}Bean2类
public class Bean2 { private static Bean2 Bean2 = new Bean2(); private Bean2() { } public static Bean2 createInstance() { return Bean2; }}Bean3类
public class Bean3 {}Bean3Factory类
public class Bean3Factory { private Bean3Factory(){ } public Bean3 getInstance(){ return new Bean3(); }}测试类InstanceDemo
import org.junit.Test;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;public class InstanceDemo { //实例化工厂方法 @Test public void demo3(){ //加载配置文件 创建工厂 ApplicationContext applicationContext=new ClassPathXmlApplicationContext("applicationContext.xml"); Bean3 bean3 =(Bean3) applicationContext.getBean("bean3"); System.out.println(bean3); } //静态工厂方法 @Test public void demo2(){ //加载配置文件 创建工厂 ApplicationContext applicationContext=new ClassPathXmlApplicationContext("applicationContext.xml"); Bean2 bean2 =(Bean2) applicationContext.getBean("bean2"); System.out.println(bean2); } //构造方法得到bean对象 @Test public void demo1(){ //加载配置文件 创建工厂 ApplicationContext applicationContext=new ClassPathXmlApplicationContext("applicationContext.xml"); Bean1 bean1 =(Bean1) applicationContext.getBean("bean1"); System.out.println(bean1); }}/* * 这三个都得到类似于com.study.spring.b_instance.Bean1@7229c204 的内存地址 */(2).Bean的其他配置:
一般情况下，装配一个Bean时，通过指定一个id属性作为Bean的名称
id 属性在IoC容器中必须是唯一的
id 的命名要满足XML对ID属性命名规范 必须以字母开始，可以使用字母、数字、连字符、下划线、句话、冒号
如果Bean的名称中含有特殊字符，就需要使用name属性 例如： <bean name="#person" class="cn.itcast.bean.Person"/>
因为name属性可以相同，所以后出现Bean会覆盖之前出现的同名的Bean
id和name的区别:
id遵守XML约束的id的约束.id约束保证这个属性的值是唯一的,而且必须以字母开始，可以使用字母、数字、连字符、下划线、句话、冒号
name没有这些要求
如果bean标签上没有配置id,那么name可以作为id.
Bean的scope属性
<!-- 3.Bean的scope属性==================== --> <bean id="product" class="com.study.spring.c_scope.Product" scope="singleton"></bean> <!-- end.Bean的scope属性=========== -->
* singleton :单例的.(默认的值.)
* prototype :多例的.
* request :web开发中.创建了一个对象,将这个对象存入request范围,request.setAttribute();
* session :web开发中.创建了一个对象,将这个对象存入session范围,session.setAttribute();
* globalSession :一般用于Porlet应用环境.指的是分布式开发.不是porlet环境,globalSession等同于session;
3.Bean属性的依赖注入
前面已经知道如何获得对象，那我们接下来要知道如果给对象对象的属性赋值。
下面通过举例说明:
Car 类
public class Car { private String name; private double price; public Car(String name, double price) { super(); this.name = name; this.price = price; } @Override public String toString() { return "Car [name=" + name + ", price=" + price + "]"; }}Car2类
public class Car2 { private String name; private double price; public void setName(String name) { this.name = name; } public void setPrice(double price) { this.price = price; } @Override public String toString() { return "Car2 [name=" + name + ", price=" + price + "]"; }}CarInfo类
public class CarInfo { public String getName(){ return "哈弗H6"; } public double caculatePrice(){ return 110000; }}CollectionBean类
import java.util.List;import java.util.Map;import java.util.Properties;import java.util.Set;public class CollectionBean { private String name; private Integer age; private List<String> hobbies; private Set<Integer> numbers; private Map<String, String> map; private Properties properties; public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } public List<String> getHobbies() { return hobbies; } public void setHobbies(List<String> hobbies) { this.hobbies = hobbies; } public Set<Integer> getNumbers() { return numbers; } public void setNumbers(Set<Integer> numbers) { this.numbers = numbers; } public Map<String, String> getMap() { return map; } public void setMap(Map<String, String> map) { this.map = map; } public Properties getProperties() { return properties; } public void setProperties(Properties properties) { this.properties = properties; } @Override public String toString() { return "CollectionBean [name=" + name + ", age=" + age + ", hobbies=" + hobbies + ", numbers=" + numbers + ", map=" + map + ", properties=" + properties + "]"; } }Employee类
public class Employee { private String name; private Car2 car2; public void setName(String name) { this.name = name; } public void setCar2(Car2 car2) { this.car2 = car2; } @Override public String toString() { return "Employee [name=" + name + ", car2=" + car2 + "]"; }}TestDi测试类
import org.junit.Test;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;public class TestDi { @Test public void demo6() { ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml"); CollectionBean collectionBean = (CollectionBean) applicationContext.getBean("collectionBean"); System.out.println(collectionBean); } @Test public void demo5() { ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml"); Car2 car2 = (Car2) applicationContext.getBean("car2_2"); System.out.println(car2); } @Test public void demo4() { ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml"); Employee e = (Employee) applicationContext.getBean("employee2"); System.out.println(e); } @Test public void demo3() { ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml"); Employee e = (Employee) applicationContext.getBean("employee"); System.out.println(e); } @Test public void demo2() { ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml"); Car2 car2 = (Car2) applicationContext.getBean("car2"); System.out.println(car2); } @Test public void demo1() { ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml"); Car car = (Car) applicationContext.getBean("car"); System.out.println(car); }}上面这几个类都不是最主要的，我们主要是来看配置文件怎么写，这才是最关键的：
applicationContext.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:p="http://www.springframework.org/schema/p" 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.xsd"> <!-- Bean的依赖注入=========== --> <!-- 4.1构造器注入 --> <bean id="car" class="com.study.spring.e_di.Car"> <!-- 方式一.根据索引的位置 --> <!-- <constructor-arg index="0" value="保时捷"></constructor-arg> <constructor-arg index="1" value="1500000"></constructor-arg> --> <!-- 方式二.根据名字配置 --> <!-- <constructor-arg name="name" value="宝马"></constructor-arg> <constructor-arg name="price" value="500000"></constructor-arg> --> <!-- 方式三.根据类型配置 --> <constructor-arg type="java.lang.String" value="奔驰"></constructor-arg> <constructor-arg type="double" value="600000"></constructor-arg> </bean> <!-- 4.2setter方法中注入 --> <bean id="car2" class="com.study.spring.e_di.Car2"> <property name="name" value="雪佛兰"></property> <property name="price" value="100000"></property> </bean> <bean id="employee" class="com.study.spring.e_di.Employee"> <property name="name" value="张三"></property> <property name="car2" ref="car2"></property> </bean> <!-- 引用p命名空间 --><!-- 如果要引用p命名，那在最上面sxd中就要配置 xmlns:p="http://www.springframework.org/schema/p"--> <bean id="car22" class="com.study.spring.e_di.Car2" p:name="宝马" p:price="500000"> </bean> <bean id="employee2" class="com.study.spring.e_di.Employee" p:name="李四" p:car2-ref="car22"></bean> <!-- 引入spEL表达式 --> <bean id="carInfo" class="com.study.spring.e_di.CarInfo"></bean> <bean id="car2_2" class="com.study.spring.e_di.Car2"> <property name="name" value="#{carInfo.name}"></property> <property name="price" value="#{carInfo.caculatePrice()}"></property> </bean> <!-- 复杂属性的依赖注入 --> <bean id="collectionBean" class="com.study.spring.e_di.CollectionBean"> <!-- 简单属性的注入 --> <property name="name" value="归谷"></property> <property name="age" value="12"></property> <!-- 注入list集合 --> <property name="hobbies"> <list> <value>吃饭</value> <value>睡觉</value> <value>敲代码</value> </list> </property> <!-- 注入set集合 --> <property name="numbers"> <set> <value>10</value> <value>20</value> <value>30</value> <value>40</value> <value>50</value> </set> </property> <!-- 注入map集合 --> <property name="map"> <map> <entry key="birthday" value="2017-1-1"></entry> <entry key="address" value="杭州西湖"></entry> <entry key="sex" value="female"></entry> </map> </property> <!-- 注入Properties --> <property name="properties"> <props> <prop key="compamy">杭州归谷</prop> <prop key="pnum">200</prop> </props> </property> </bean> <!-- end Bean的依赖注入============ --> <import resource="classpath:bean1.xml"/> <import resource="classpath:bean2.xml"/> <!-- 这里导入是指如果在src下还有其它的beans.xml我们可以这样去调用 --> </beans>有关applicationContext.xml这个配置文件里的内容一定要看懂，我写的还是比较基础和全面的。
有关命名空间p的使用我这里在解释下：
p:<属性名>="xxx" 引入常量值
p:<属性名>-ref="xxx" 引用其它Bean对象
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持VeVb武林网。
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