1、IoC容器简介
控制反转IoC（Inversion of Control）又称依赖注入DI（dependency injection），由org.springframework.beans和org.springframework.context基础包构成了IoC容器，其中BeanFactory接口提供了一种先进的配置机制能够管理任何类型的对象，ApplicationContext是BeanFactory的一个子类，它更加简便的集成了Spring的AOP特性，通常情况下使用ApplicationContext，因为它提供了BeanFactory的完整超集，如果想用BeanFactory替代ApplicationContext可以参考 Section 6.16, “The BeanFactory”
Spring IoC容器工作图描述
Paste_Image.png
2、源数据（Metadata）配置
可以基于以下三种方式配置：
- xml注入
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" 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">
<bean id="..." class="..."> <!-- collaborators and configuration for this bean go here -->
</bean>
<bean id="..." class="..."> <!-- collaborators and configuration for this bean go here -->
</bean> <!-- more bean definitions go here -->
</beans>
允许组合多个bean配置xml
<beans>
<import resource="services.xml"/>
<import resource="resources/messageSource.xml"/>
<import resource="/resources/themeSource.xml"/>
<bean id="bean1" class="..."/>
<bean id="bean2" class="..."/>
</beans>
使用容器加载bean
// create and configure beans
ApplicationContext context = new ClassPathXmlApplicationContext(new String[] {"services.xml", "daos.xml"});
// retrieve configured instance
PetStoreService service = context.getBean("petStore", PetStoreService.class);
// use configured instance
List<String> userList = service.getUsernameList();
<?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.xsd">
<context:annotation-config/>
</beans>
@Configuration
public class AppConfig {
@Bean
public MyService myService() {
return new MyServiceImpl();
}
}
加载bean
ApplicationContext ctx = new AnnotationConfigApplicationContext(AppConfig.class);
MyService myService = ctx.getBean(MyService.class);
myService.doStuff();
3、实例化bean
- 通过构造函数实例化
<bean id="exampleBean" class="examples.ExampleBean"/>
- 通过静态方法实例化
java code
public class ClientService {
private static ClientService clientService = new ClientService();
private ClientService() {}
public static ClientService createInstance() {
return clientService;
}
}
xml配置
<bean id="clientService" class="examples.ClientService" factory-method="createInstance"/>
静态方法带参数(通过constructor-arg传入参数)
java code
public class ExampleBean {
// a private constructor
private ExampleBean(...) { ... }
// a static factory method; the arguments to this method can be
// considered the dependencies of the bean that is returned,
// regardless of how those arguments are actually used.
public static ExampleBean createInstance (
AnotherBean anotherBean, YetAnotherBean yetAnotherBean, int i) {
ExampleBean eb = new ExampleBean (...);
// some other operations... return eb;
}
}
xml 配置
<bean id="exampleBean" class="examples.ExampleBean" factory-method="createInstance">
<constructor-arg ref="anotherExampleBean"/>
<constructor-arg ref="yetAnotherBean"/>
<constructor-arg value="1"/>
</bean>
<bean id="anotherExampleBean" class="examples.AnotherBean"/>
<bean id="yetAnotherBean" class="examples.YetAnotherBean"/>
- 通过普通方法实例化
java code
public class DefaultServiceLocator {
private static ClientService clientService = new ClientServiceImpl();
private DefaultServiceLocator() {}
public ClientService createClientServiceInstance() {
return clientService;
}
}
xml配置
<!-- the factory bean, which contains a method called createInstance() -->
<bean id="serviceLocator" class="examples.DefaultServiceLocator">
<!-- inject any dependencies required by this locator bean -->
</bean>
<!-- the bean to be created via the factory bean -->
<bean id="clientService" factory-bean="serviceLocator" factory-method="createClientServiceInstance"/>
4、依赖注入
- 基于构造器的注入
普通类型的参数
java code
package x.y;
public class Foo {
public Foo(Bar bar, Baz baz) {
// ...
}
}
xml配置
<beans>
<bean id="foo" class="x.y.Foo">
<constructor-arg ref="bar"/>
<constructor-arg ref="baz"/>
</bean>
<bean id="bar" class="x.y.Bar"/>
<bean id="baz" class="x.y.Baz"/>
</beans>
基本数据类型的参数
java code
package examples;
public class ExampleBean {
// Number of years to calculate the Ultimate Answer
private int years;
// The Answer to Life, the Universe, and Everything
private String ultimateAnswer;
public ExampleBean(int years, String ultimateAnswer) {
this.years = years; this.ultimateAnswer = ultimateAnswer;
}
}
xml配置-type
<bean id="exampleBean" class="examples.ExampleBean">
<constructor-arg type="int" value="7500000"/>
<constructor-arg type="java.lang.String" value="42"/>
</bean>
xml配置-index
<bean id="exampleBean" class="examples.ExampleBean">
<constructor-arg index="0" value="7500000"/>
<constructor-arg index="1" value="42"/>
</bean>
xml配置-name
<bean id="exampleBean" class="examples.ExampleBean">
<constructor-arg name="years" value="7500000"/>
<constructor-arg name="ultimateAnswer " value="42"/>
</bean>
注意，基于那么的注入，如果你的编译不是以debug方式编译，那么参数名是会变掉，这时候需要通过jdk注解指定编译后的参数名
package examples;
public class ExampleBean {
// Fields omitted
@ConstructorProperties({"years", "ultimateAnswer"})
public ExampleBean(int years, String ultimateAnswer) {
this.years = years;
this.ultimateAnswer = ultimateAnswer;
}
}
- 基于setter的注入
java code
public class SimpleMovieLister {
// the SimpleMovieLister has a dependency on the MovieFinder
private MovieFinder movieFinder;
// a setter method so that the Spring container can inject a MovieFinder
public void setMovieFinder(MovieFinder movieFinder) {
this.movieFinder = movieFinder;
}
// business logic that actually uses the injected MovieFinder is omitted...
}
xml配置
<bean id="simpleMovieLister" class="examples.SimpleMovieLister">
<!-- setter injection using the nested ref element -->
<property name="movieFinder">
<ref bean="movieFinderBean"/>
</property>
</bean>
<bean id="movieFinderBean" class="examples.MovieFinder"/>
该方式依赖注入由容器调用setter方法将匹配参数类型的bean注入进去，所以该方式注入会在其它构造器注入之后之后注入
