java框架篇---sPRing IOC依赖注入spring依赖注入的方式有4种
构造方法注入属性注入工厂注入注解注入下面通过一个实例统一讲解：
User.java
package com.bjsxt.model;public class User { private String username; private String passWord; public User(){} public User(String username, String password) { super(); this.username = username; this.password = password; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } @Override public String toString() { return "User [username=" + username + ", password=" + password + "]"; }}
UserDAO.java
package com.bjsxt.dao;import com.bjsxt.model.User;public interface UserDAO { public void save(User user);}
UserDAO实现类UserDAOImpl
package com.bjsxt.dao.impl;import com.bjsxt.dao.UserDAO;import com.bjsxt.model.User;public class UserDAOImpl implements UserDAO { public void save(User user) { //Hibernate //JDBC //xml //NetWork System.out.println("user saved!"); }}
工厂类
第一个：UserFactory
package com.bjsxt.factory;import com.bjsxt.model.User;public class UserFactory { public User CreatUser () { User user=new User(); user.setUsername("周1"); user.setPassword("oumyye"); return user; }}
第二个：UserFactory2
package com.bjsxt.factory;import com.bjsxt.model.User;public class UserFactory2 { public static User CreatUser () { User user=new User(); user.setUsername("偶my耶1"); user.setPassword("oumyye"); return user; }}
控制层：UserService
package com.bjsxt.service;import com.bjsxt.dao.UserDAO;import com.bjsxt.model.User;public class UserService { private UserDAO userDAO; public void init() { System.out.println("###########init"); } public void save(User user) { userDAO.save(user); } public UserDAO getUserDAO() { return userDAO; } public void setUserDAO(UserDAO userDAO) { this.userDAO = userDAO; } public UserService(UserDAO userDAO) { super(); this.userDAO = userDAO; } public void destroy() { System.out.println("destroy"); }}
配置文件：bean.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" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd"> <!-- 构造方法注入 --> <bean id="user" class="com.bjsxt.model.User" > <constructor-arg index="0" type="String" value="zhou"></constructor-arg> <constructor-arg index="1" type="String" value="password"></constructor-arg> </bean> <!-- 属性注入 --> <bean id="user1" class="com.bjsxt.model.User" > <property name="username" value="zhang"></property> <property name="password" value="oumyye"></property> </bean> <!-- 工厂注入 --> <bean id= "userFactory" class="com.bjsxt.factory.UserFactory" > </bean> <bean id="user2" factory-bean="userFactory" factory-method="CreatUser"></bean> <!-- 静态工厂注入 --> <bean id= "user3" class="com.bjsxt.factory.UserFactory2" factory-method="CreatUser"> </bean> <bean id="u" class="com.bjsxt.dao.impl.UserDAOImpl"></bean> <bean id="userService" class="com.bjsxt.service.UserService" init-method="init" destroy-method="destroy" scope="prototype"> <!-- <property name="userDAO" ref="u" /> --> <!-- 构造方法注入 --> <constructor-arg> <ref bean="u"/> </constructor-arg> </bean> </beans>
测试类：
package com.bjsxt.service;import static org.junit.Assert.*;import org.junit.Test;import org.springframework.context.applicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;import com.bjsxt.model.User;public class UserServiceTest { @Test public void test() { ApplicationContext applicationContext=new ClassPathXmlApplicationContext("beans.xml"); UserService userService=(UserService) applicationContext.getBean("userService"); //构造方法注入 User user=(User) applicationContext.getBean("user"); //属性注入 User user1=(User) applicationContext.getBean("user1"); //工厂注入 User user2=(User) applicationContext.getBean("user2"); //工厂注入 User user3=(User) applicationContext.getBean("user3"); System.out.println(user); System.out.println(user1); System.out.println(user2); System.out.println(user3); userService.save(user); userService.destroy(); }}
结果：
###########initUser [username=zhou, password=password]User [username=zhang, password=oumyye]User [username=周1, password=oumyye]User [username=偶my耶1, password=oumyye]user saved!destroy
注解方式在后面详细介绍
依赖注入—自动装配Spring中提供了自动装配依赖对象的机制，但是在实际应用中并不推荐使用自动装配，因为自动装配会产生未知情况，开发人员无法预见最终的装配结果。
自动装配是在配置文件中实现的，如下：
<beanid="***"class="***"autowire="byType">
只需要配置一个autowire属性即可完成自动装配，不用再配置文件中写<property>,但是在类中还是要生成依赖对象的setter方法。
Autowire的属性值有如下几个：
·byType按类型装配可以根据属性类型，在容器中寻找该类型匹配的bean，如有多个，则会抛出异常，如果没有找到，则属性值为null；
·byName按名称装配可以根据属性的名称在容器中查询与该属性名称相同的bean，如果没有找到，则属性值为null；
·constructor与byType方式相似，不同之处在与它应用于构造器参数，如果在容器中没有找到与构造器参数类型一致的bean，那么将抛出异常；
·autodetect通过bean类的自省机制(introspection)来决定是使用constructor还是byType的方式进行自动装配。如果发现默认的构造器，那么将使用byType的方式。