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:
###########init User [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:
<bean id="***" 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。
原文地址:https://www.cnblogs.com/jiangzhaowei/p/9629818.html
时间: 2024-11-06 09:48:43