通过Java类设置配置信息，JavaConfig

Spring常用的通过XML或者@Controller、@Servoce、@Repository、@Component等注解注册Bean，最近看Spring Session的源码，知道还有JavaConfig注册Bean的方式，就是通过@Configuration、@Bean注册Bean。

引用依赖包：

<dependencies>

    <dependency>

        <groupId>org.springframework</groupId>

        <artifactId>spring-context</artifactId>

        <version>3.2.10.RELEASE</version>

    </dependency>

    <dependency>

        <groupId>org.springframework</groupId>

        <artifactId>spring-webmvc</artifactId>

        <version>3.2.10.RELEASE</version>

    </dependency>

    <dependency>

        <groupId>commons-beanutils</groupId>

        <artifactId>commons-beanutils</artifactId>

        <version>1.9.2</version>

    </dependency>

    <dependency>

        <groupId>javax.servlet</groupId>

        <artifactId>javax.servlet-api</artifactId>

        <version>3.0.1</version>

    </dependency>

</dependencies>

这个类是配置Bean的：

package com.nicchagil;

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Configuration;

@Configuration

public class UserConfiguration {

    @Bean

    public UserService userService(UserDAO userDAO) {

        return new UserService();

    }

    @Bean

    public UserDAO userDAO() {

        return new UserDAO();

    }

}

这两个Bean是这样的：

package com.nicchagil;

public class UserDAO {

}

package com.nicchagil;

public class UserService {

}

这个BeanPostProcessor是用于看Bean有没有实例化的，与JavaConfig本身没什么关系：

package com.nicchagil;

import java.util.logging.Logger;

import org.springframework.beans.BeansException;

import org.springframework.beans.factory.config.BeanPostProcessor;

public class MyBeanPostProcessor implements BeanPostProcessor {

    Logger logger = Logger.getLogger("MyBeanPostProcessor");

    public Object postProcessBeforeInitialization(Object obj, String arg1)

            throws BeansException {

        return obj;

    }

    public Object postProcessAfterInitialization(Object obj, String arg1)

            throws BeansException {

        if (obj != null) {

            logger.info("实例化：" + obj + ", Class：" + obj.getClass().getName());

        }

        return obj;

    }

}

记得要注册扫描包的路径：

<?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-3.0.xsd

           http://www.springframework.org/schema/context

           http://www.springframework.org/schema/context/spring-context-3.0.xsd">

    <!-- scan the component from the base package -->

    <context:component-scan base-package="com.nicchagil" />

    <bean id="myBeanPostProcessor" class="com.nicchagil.MyBeanPostProcessor" />

</beans>

测试类：

package com.nicchagil;

import java.util.logging.Logger;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class HowToUse {

    public static Logger LOGGER = Logger.getLogger("HowToUse");

    public static void main(String[] args) {

        ApplicationContext context =

                new ClassPathXmlApplicationContext("spring.xml");

        UserDAO userDAO = context.getBean("userDAO", UserDAO.class);

        LOGGER.info("userDAO : " + userDAO);

        UserService userService = context.getBean("userService", UserService.class);

        LOGGER.info("userService : " + userService);

    }

}

运行日志：

六月 11, 2017 3:41:57 下午 org.springframework.context.support.AbstractApplicationContext prepareRefresh

信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@37f8bb67: startup date [Sun Jun 11 15:41:57 CST 2017]; root of context hierarchy

六月 11, 2017 3:41:57 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions

信息: Loading XML bean definitions from class path resource [spring.xml]

六月 11, 2017 3:41:58 下午 org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons

信息: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@1d057a39: defining beans [userConfiguration,org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,myBeanPostProcessor,org.springframework.context.annotation.ConfigurationClassPostProcessor.importAwareProcessor,userService,userDAO]; root of factory hierarchy

六月 11, 2017 3:41:58 下午 com.nicchagil.MyBeanPostProcessor postProcessAfterInitialization

信息: 实例化：com.nicchagil.UserConfiguration$$EnhancerBySpringCGLIB$$cd2ac8bb@32eebfca, Class：com.nicchagil.UserConfiguration$$EnhancerBySpringCGLIB$$cd2ac8bb

六月 11, 2017 3:41:58 下午 com.nicchagil.MyBeanPostProcessor postProcessAfterInitialization

信息: 实例化：com.nicchagil.UserDAO@47db50c5, Class：com.nicchagil.UserDAO

六月 11, 2017 3:41:58 下午 com.nicchagil.MyBeanPostProcessor postProcessAfterInitialization

信息: 实例化：com.nicchagil.UserService@149494d8, Class：com.nicchagil.UserService

六月 11, 2017 3:41:58 下午 com.nicchagil.HowToUse main

信息: userDAO : com.nicchagil.UserDAO@47db50c5

六月 11, 2017 3:41:58 下午 com.nicchagil.HowToUse main

信息: userService : com.nicchagil.UserService@149494d8

自定义逻辑创建Bean的工厂Bean，FactoryBean

引入POM：

<dependency>

    <groupId>org.springframework</groupId>

    <artifactId>spring-context</artifactId>

    <version>3.2.10.RELEASE</version>

</dependency>

声明实体：

package com.nicchagil.factorybeanexercise;

public class User {

    private Integer id;

    private String name;

    public Integer getId() {

        return id;

    }

    public void setId(Integer id) {

        this.id = id;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    @Override

    public String toString() {

        return "User [id=" + id + ", name=" + name + "]";

    }

}

定义工厂：

package com.nicchagil.factorybeanexercise;

import org.springframework.beans.factory.FactoryBean;

public class UserFactoryBean implements FactoryBean<User> {

    /**

     * 获取对象

     */

    @Override

    public User getObject() throws Exception {

        User user = new User();

        user.setId(123);

        user.setName("Nick Huang");

        return user;

    }

    /**

     * 获取对象的类型

     */

    @Override

    public Class<?> getObjectType() {

        return User.class;

    }

    /**

     * 对象是否单例

     */

    @Override

    public boolean isSingleton() {

        return true;

    }

}

注册工厂：

<?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-3.0.xsd

           http://www.springframework.org/schema/context

           http://www.springframework.org/schema/context/spring-context-3.0.xsd">

    <bean id="user" class="com.nicchagil.factorybeanexercise.UserFactoryBean" />

</beans>

测试类：

package com.nicchagil.factorybeanexercise;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class HowToTest {

    public static void main(String[] args) {

        @SuppressWarnings("resource")

        ApplicationContext ac = new ClassPathXmlApplicationContext("spring.xml");

        User user = ac.getBean("user", User.class);

        System.out.println(user);

    }

}