spring注解开发

spring的bean管理（注解）

注解介绍：

1.  代码里面特殊标记，使用注解可以完成功能
2.  注解写法@注解名称（属性名=属性名）
3.  注解使用类上面，方法上面和属性下面

spring注解开发准备：

1、导入jar包(4个核心包，与两个日志包)，导入aop的jar包

2、创建类，创建方法

3、创建spring配置文件，引入约束

(1)做ioc的基本功能，引入约束beans

打开G:\spring-framework-4.3.7.RELEASE\docs\spring-framework-reference\html，里面的最后一个文件，找到该部分，粘贴：

(2)做spring的ioc注解开发，引入新的约束

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"    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 definitions here --><!-- 开启注解扫描(包含类，方法，属性) --><context:component-scan base-package="cn.itcast.anno"></context:component-scan></beans>

User.java

@Component(value = "user")// 相当于<bean id="user" class="  "></bean>public class User {public void add() {System.out.println("add()");}}

测试:

public class TestAnno {public static void main(String[] args) {ApplicationContext context = new ClassPathXmlApplicationContext("bean2.xml");User user = (User) context.getBean("user");user.add();System.err.println(user);}}

创建对象有四个注解：

spring中提供@Component的三个衍生注解（功能来讲一样）：

1. @controller     web层
2. @service         业务层
3. @Repository   持久层

这三个注解是为了让标注类本身的用途清晰，spring在后续版本对其增强：

注解注入属性：

1、创建service类，创建dao类，在service得到dao对象

进入属性第一个注解@Autowored

UserDao.java

@Component(value = "userdao")public class UserDao {public void add() {System.out.println("userdao.add()");}}

UserService.java

@Service(value="userservice")public class UserService {@Autowiredprivate UserDao userDao;public void add(){System.out.println("service");userDao.add();}}

测试：

public class TestAnno2 {public static void main(String[] args) {ApplicationContext context = new ClassPathXmlApplicationContext("bean2.xml");UserService userService = (UserService) context.getBean("userservice");userService.add();}}

2、注入属性第二个注解，@Resource

UserDao.java

@Component(value = "userdao")public class UserDao {public void add() {System.out.println("userdao.add()");}}

UserService.java

@Service(value="userservice")public class UserService {@Resource(name="userdao")private UserDao userDao;public void add(){System.out.println("service");userDao.add();}}

测试：

public class TestAnno2 {public static void main(String[] args) {ApplicationContext context = new ClassPathXmlApplicationContext("bean2.xml");UserService userService = (UserService) context.getBean("userservice");userService.add();}}

配置文件和注解混合使用：

1、创建对象操作使用配置文件方式实现

2、注入属性操作使用注解方式实现

BookSerivce.java

public class BookService {@Resource(name="bookDao")private BookDao bookDao;@Resource(name="orderDao")private OrderDao orderDao;public void add(){System.out.println("bookservice");bookDao.book();orderDao.buy();}}

BookDao.java

public class BookDao {public void book(){System.out.println("book dao");}}

OrderDao.java

public class OrderDao {public void buy(){System.out.println("orderdao.buy()");}}

bean2.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: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 definitions here --><!-- 开启注解扫描(包含类，方法，属性) --><context:component-scan base-package="cn.itcast.anno"></context:component-scan><!-- 配置对象 --><bean id="bookService" class="cn.itcast.anno.BookService"></bean><bean id="bookDao" class="cn.itcast.anno.BookDao"></bean><bean id="orderDao" class="cn.itcast.anno.OrderDao"></bean></beans>

测试：

public class TestAnno3 {public static void main(String[] args) {ApplicationContext context = new ClassPathXmlApplicationContext("bean2.xml");BookService bookService  = (BookService) context.getBean("bookService");bookService.add();}}