spring笔记

• Spring依赖注入（DI）   

1. Setter方法注入

   接口、实现类和Helper类：

   // 接口public interface People {  public void talk();}

   // 实现类public class American implements People {  public void talk() {    System.out.println("Hello,I'm an American");  }}

   // Helper类public class TalkHelper {  People people;  public TalkHelper(People people) {    this.people = people;  }  public void setPeople(People people) {    this.people = people;  }  public void talk() {    people.talk();  }}

   
   Spring 配置：

   <beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans-2.5.xsd"><bean id="OutputHelper" class="com.winne.talk.TalkHelper"><property name="people" ref="American" /></bean><bean id="American" class="com.winne.talk.impl.American" /></beans>

   Test：
   

   import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;import com.yiibai.output.OutputHelper;public class App {public static void main(String[] args) {ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");                 TalkHelper talkHelper = (TalkHelper)context.getBean("TalkHelper");            talkHelper.talk();}}

   
   
   结果：
   Hello,I'm an American

2. 构造器注入 Spring配置：

   <beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans-2.5.xsd"><bean id="TalkHelper" class="com.winne.talk.TalkHelper"><constructor-arg><ref bean="American" /></constructor-arg></bean><bean id="American" class="com.winne.talk.American" /></beans>

注：有多参数多构造方法的类使用构造器注入可能会导致类型歧义，解决方案见我的另一篇文章。

• Spring Bean 

• Spring EL 

两个简单的bean：

public class People {  private House house;  private String houseAddr;}

public class House {  private String addr;  private int yearLimit;}

XML形式：

<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans-3.0.xsd"><bean id="houseBean" class="com.winne.core.House"><property name="addr" value="Hangzhou" /><property name="yearLimit" value="50" /></bean><bean id="peopleBean" class="com.winne.core.People"><property name="house" value="#{houseBean}" /><property name="houseAddr" value="#{houseBean.addr}" /></bean></beans>

结果：

winne的house即houseBean，houseAddr为Hangzhou，houseBean的addr为Hangzhou，yearLimit为50.（我这么说，聪明的你一定看的懂）

注解形式：

@Component("peopleBean")public class People {  @Value("#{houseBean}")  private House house;  @Value("#{houseBean.addr}")  private String houseAddr;  // do something}

@Component("houseBean")public class House {  @Value("Hangzhou") // 直接注入字符串  private String addr;  @Value("50") // 直接注入整型  private int yearLimit;  // do something}

<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/beanshttp://www.springframework.org/schema/beans/spring-beans-3.0.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context-3.0.xsd"><context:component-scan base-package="com.winne.core" /></beans>

注：如果bean是在XML里注册的，但@Value是定义在Java类里的，那么该@Value就不会执行咯~~

还可以调用方法@Value("#{houseBean.toString()}")，支持大多数标准的数学，逻辑和关系运算符（==,!=,<,>,<=,>=,and,or,!,+,-,*,/,%,^），以及三元操作符（...?A:B），取list（@Value("#{testBean.xxxList[0]}")）或map（@Value("#{testBean.xxxMap['key1']}")），还可以支持正则表达式@Value("#{'100' matches '\\d+'}")

• Spring自动组件扫描

XML配置：

<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans-2.5.xsd"><bean id="userService" class="com.winne.user.service.UserService"><property name="userDAO" ref="userDAO" /></bean><bean id="userDAO" class="com.winne.user.dao.UserDAO" /></beans>

自动组件扫描：

import org.springframework.stereotype.Component;@Componentpublic class UserDAO {@Overridepublic String toString() {return "Hello , This is UserDAO";}}

import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Component;import com.winne.user.dao.UserDAO;@Componentpublic class UserService {@AutowiredUserDAO userDAO;@Overridepublic String toString() {return "UserService [userDAO=" + userDAO + "]";}} 

<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/beanshttp://www.springframework.org/schema/beans/spring-beans-2.5.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context-2.5.xsd"><!-- 在 Spring 中启用自动扫描功能 base-package指明存储组件，Spring将扫描这个文件夹，找出注解了@Component的bean并注册到spring容器 --><context:component-scan base-package="com.winne.user" /></beans>

在Spring2.5中，有4种类型的组件自动扫描注释类型@Component – 指示自动扫描组件。@Repository – 表示在持久层DAO组件。@Service – 表示在业务层服务组件。@Controller – 表示在表示层控制器组件。

其实，你都注册成@Component，也是没问题的。但为了便于阅读，还是该声明成哪个就声明成哪个吧。

另，如果你想修改组件的名字，可以这样做，例@Service("XXX")。