Spring注解驱动开发（三）
Posted Spring8 minutes read (About 1249 words)

Spring注解驱动开发（三）

The Spring Framework provides a comprehensive programming and configuration model for modern Java-based enterprise applications - on any kind of deployment platform.

属性赋值@value赋值

使用@Value赋值

  • 基本数值
  • 可以写SPEL表达式 #{}
  • 可以${}获取配置文件信息（在运行的环境变量中的值）

使用xml时候导入配置文件是

<context:property-placeholder location="classpath:person.properties"/>

使用注解可以在配置类添加一个@PropertySource注解把配置文件中k/v保存到运行的环境中

使用${key}来获取

/**
 * @Author: cuzz
 * @Date: 2018/9/24 18:43
 * @Description:
 */
@PropertySource(value = {"classpath:/person.properties"})
@Configuration
public class MainConfigOfPropertyValue {

    @Bean
    public Person person() {
        return new Person();
    }
}

Person 类

@Data
public class Person {

    @Value("vhuj")
    private String name;

    @Value("#{20-2}")
    private Integer age;

    @Value("${person.nickName}")
    private String nickName;
}

测试

@Test
public void test01() {
    printBean(applicationContext);
    System.out.println("---------------------------");

    Person person = (Person) applicationContext.getBean("person");
    System.out.println(person);

    System.out.println("---------------------------");

}

输出

---------------------------
Person(name=vhuj, age=18, nickName=三三)
---------------------------

自动装配@Autowired@Qualifier@Primary

自动转配：

Spring利用依赖注入（DI），完成对IOC容器中各个组件的依赖关系赋值

@Autowired自动注入:

  • a. 默认优先按照类型去容器中寻找对应的组件，如果找到去赋值

  • b. 如果找到到相同类型的组件，再将属性名（BookDao bookdao）作为组件的id去容器中查找

  • c. 接下来还可以使用@Qualifier("bookdao")明确指定需要装配的id

  • d. 默认是必须的，我们可以指定 @Autowired(required=false)，指定非必须

@Primary让Spring自动装配时首先装配

自动装配@Resource和@Inject

Spring还支持使用@Resource (JSR250) 和@Inject (JSR330) 注解，这两个是java规范

@Resource和@Autowired一样实现自动装配功能，默认是按组件名称进行装配的

没有支持@Primary和@Autowird(required=false)的功能

自动装配其他地方的自动装配

@Autowired：构造器、参数、方法属性等

标注到方法位子上@Bean+方法参数，参数从容器中获取

/**
 * @Author: cuzz
 * @Date: 2018/9/24 20:57
 * @Description:
 */
public class Boss {
    // 属性
    @Autowired
    private Car car;
    
    // 构造器 如果构造器只有一个有参构造器可以省略
    @Autowired
    public Boss(@Autowired Car car) {
    }

    public Car getCar() {
        return car;
    }
    
    // set方法
    @Autowired         // 参数
    public void setCar(@Autowired Car car) {
        this.car = car;
    }
}

自动装配Aware注入Spring底层注解

自定义组件想要使用Spring容器底层的一些组件（ApplicationContext，BeanFactory 等等），自定义组件实现xxxAware，在创建对象的时候会调用接口规定的方法注入相关的组件

/**
 * Marker superinterface indicating that a bean is eligible to be
 * notified by the Spring container of a particular framework object
 * through a callback-style method. Actual method signature is
 * determined by individual subinterfaces, but should typically
 * consist of just one void-returning method that accepts a single
 * argument.
 */
public interface Aware {

}

我们实现几个常见的Aware接口

/**
 * @Author: cuzz
 * @Date: 2018/9/25 10:18
 * @Description:
 */
@Component
public class Red implements BeanNameAware ,BeanFactoryAware, ApplicationContextAware {
    private ApplicationContext applicationContext;

    @Override
    public void setBeanName(String name) {
        System.out.println("当前Bean的名字: " + name);
    }

    @Override
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        System.out.println("当前的BeanFactory: " + beanFactory);
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
        System.out.println("传入的ioc: " + applicationContext);
    }
}

注入到配置中测试

/**
 * @Author: cuzz
 * @Date: 2018/9/25 10:28
 * @Description:
 */
public class IOCTestAware {

    @Test
    public void test01() {
        AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(MainConfigOfAware.class);

    }
}

测试结果

当前Bean的名字: red
当前的BeanFactory: org.springframework.beans.factory.support.DefaultListableBeanFactory@159c4b8: defining beans [org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.context.event.internalEventListenerProcessor,org.springframework.context.event.internalEventListenerFactory,mainConfigOfAware,red]; root of factory hierarchy
传入的ioc: org.springframework.context.annotation.AnnotationConfigApplicationContext@1e89d68: startup date [Tue Sep 25 10:29:17 CST 2018]; root of context hierarchy

把Spring自定义组件注入到容器中

原理：

public interface ApplicationContextAware extends Aware {}

通过 Debug 方式，定位到 org.springframework.context.support.ApplicationContextAwareProcessor#postProcessBeforeInitialization

@Override
public Object postProcessBeforeInitialization(final Object bean, String beanName) throws BeansException {
    AccessControlContext acc = null;

    if (System.getSecurityManager() != null &&
            (bean instanceof EnvironmentAware || bean instanceof EmbeddedValueResolverAware ||
                    bean instanceof ResourceLoaderAware || bean instanceof ApplicationEventPublisherAware ||
                    bean instanceof MessageSourceAware || bean instanceof ApplicationContextAware)) {
        acc = this.applicationContext.getBeanFactory().getAccessControlContext();
    }

    if (acc != null) {
        AccessController.doPrivileged(new PrivilegedAction<Object>() {
            @Override
            public Object run() {
                invokeAwareInterfaces(bean);
                return null;
            }
        }, acc);
    }
    else {
        invokeAwareInterfaces(bean); // 调用
    }

调用下面方法进行判断，每种 xxxAware 接口中只有一种方法，并调用相应的方法

private void invokeAwareInterfaces(Object bean) {
    if (bean instanceof Aware) {
        if (bean instanceof EnvironmentAware) {
            ((EnvironmentAware) bean).setEnvironment(this.applicationContext.getEnvironment());
        }
        if (bean instanceof EmbeddedValueResolverAware) {
            ((EmbeddedValueResolverAware) bean).setEmbeddedValueResolver(this.embeddedValueResolver);
        }
        if (bean instanceof ResourceLoaderAware) {
            ((ResourceLoaderAware) bean).setResourceLoader(this.applicationContext);
        }
        if (bean instanceof ApplicationEventPublisherAware) {
            ((ApplicationEventPublisherAware) bean).setApplicationEventPublisher(this.applicationContext);
        }
        if (bean instanceof MessageSourceAware) {
            ((MessageSourceAware) bean).setMessageSource(this.applicationContext);
        }
        if (bean instanceof ApplicationContextAware) {
            ((ApplicationContextAware) bean).setApplicationContext(this.applicationContext);
        }
    }
}

xxxAware都是通过xxxProcessor来处理的

比如：ApplicationContextAware 对应 ApplicationContextAwareProcessor

自动装配@Profile环境搭建

Profile是Spring为我们提供可以根据当前环境，动态的激活和切换一系组件的功能

a. 使用命令动态参数激活：虚拟机参数位子加载 -Dspring.profiles.active=test

b. 使用代码激活环境

我们想配置类

/**
 * @Author: cuzz
 * @Date: 2018/9/25 10:47
 * @Description:
 */
@Configuration
public class MainConfigOfProfile {

    @Profile(value = "test")
    @Bean(value = "testDataSource")
    public DataSource testDataSource() {

        System.out.println("testDataSource");
        return null;
    }

    @Profile(value = "dev")
    @Bean(value = "devDataSource")
    public DataSource devDataSource() {
        System.out.println("devDataSource");
        return null;
    }
}

测试

/**
 * @Author: cuzz
 * @Date: 2018/9/25 10:59
 * @Description:
 */
public class IOCTestProfile {

    @Test
    public void test01() {
        // 1. 使用无参构造器创建一个applicationContext
        AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext();
        // 2. 设置要激活的环境
        applicationContext.getEnvironment().setActiveProfiles("test");
        // 3. 注册主配置类
        applicationContext.register(MainConfigOfProfile.class);
        // 4. 启动刷新容器
        applicationContext.refresh();
    }
}

输出

testDataSource
#

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