2.走向自动装配

时间 2019-12-04

标签走向自动装配繁體版

原文原文链接

2.走向自动装配

Spring 模式注解装配

2-1 走向自动装配

课程介绍java
- spring framework手动装配
- spring boot自动装配
- spring boot自动装配是以spring framework手动装配为基础实现的

2-2 Spring Framework 手动装配

[模式注解（Stereotype Annotations)]()

A *stereotype annotation is an annotation that is used to declare the role that a component plays within the application. For example, the @Repository annotation in the Spring Framework is a marker for any class that fulfills the role or stereotype* of a repository (also known as Data Access Object or DAO).
@Component is a generic stereotype for any Spring-managed component. Any component annotated with @Component is a candidate for component scanning. Similarly, any component annotated with an annotation that is itself meta-annotated with @Component is also a candidate for component scanning. For example, @Service is meta-annotated with @Component.web

模式注解是一种用于声明在应用中扮演“组件”角色的注解。如 Spring Framework 中的 @Repository 标注在任何类上，用于扮演仓储角色的模式注解。
@Component 做为一种由 Spring 容器托管的通用模式组件，任何被 @Component 标注的组件均为组件扫描的候选对象。相似地，凡是被 @Component 元标注（meta-annotated）的注解，也即被@Component 注解标注过的注解，如 @Service ，且这两个注解的签名也一致时，当任何组件标注它时，也被视做组件扫描的候选对象。

模式注解举例

Spring Framework 注解	场景说明	起始版本
@Repository	数据仓储模式注解	2.0
@Component	通用组件模式注解	2.5
@Service	服务模式注解	2.5
@Controller	Web 控制器模式注解	2.5
@Configuration	配置类模式注解	3.0

装配方式

`<context:component-scan>` 方式

<?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/springcontext.xsd">
<!-- 激活注解驱动特性 -->
        <context:annotation-config />
<!-- 找寻被 @Component 或者其派生 Annotation 标记的类（Class），将它们注册为 Spring Bean -->
        <context:component-scan base-package="com.imooc.dive.in.spring.boot" />
        </beans>

@ComponentScan 方式

@ComponentScan(basePackages = "com.imooc.dive.in.spring.boot")
public class SpringConfiguration {
...
}

2-3 Spring Framework手动装配自定义模式注解

自定义模式注解

@firstLevelRepository注解“继承”了@repository，同时@repository注解又“继承”了@component，三个注解在注解关系上层层“继承”，同时注解的签名字段即注解属性方法也一致，只有一个value字段，用于指定bean的name。同理，@SecondLevelRepository注解被@FirstLevelRepository注解标注也会有一样的效果，体现了层次性。 “派生性”侧重于从spring已有的注解生成新的注解，“层次性”侧重于这些注解之间所谓的层层”继承“关系。

`@Component` “派生性”

FirstLevelRepository注解定义

package com.imooc.springbootautoconfigure.annotation;
import org.springframework.stereotype.Repository;
import java.lang.annotation.*;
/**
 * 一级 {@link Repository @Repository}
 *
 * @author gaorj
 * @since 2018/10/16
 */
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Repository
public @interface FirstLevelRepository {

    String value() default "";

}

`@Component` “层次性”

@SecondLevelRepository注解定义

package com.imooc.springbootautoconfigure.annotation;

import java.lang.annotation.*;

/**
 * @author gaorj
 * @since 2018/10/16
 */
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@FirstLevelRepository
public @interface SecondLevelRepository {

    String value() default "";

}

两个自定义注解的使用

package com.imooc.springbootautoconfigure.repository;

import com.imooc.springbootautoconfigure.annotation.FirstLevelRepository;
import com.imooc.springbootautoconfigure.annotation.SecondLevelRepository;
import org.springframework.stereotype.Component;

/**
 *
 * @author gaorj
 * @since 2018/10/16
 */
//@FirstLevelRepository(value = "myFirstLevelRepository")//value指定bean的名称
//@Component(value = "myFirstLevelRepository")//一样的效果，注解的派生性
@SecondLevelRepository(value = "myFirstLevelRepository")//一样的效果，注解的层次性
public class MyFirstLevelRepository {
}

Repository启动类的使用，用于验证自定义注解的使用。此处没有使用默认的@SpringBootApplication注解，使用SpringApplicationBuilder初始化上下文

package com.imooc.springbootautoconfigure.bootstrap;

import com.imooc.springbootautoconfigure.repository.MyFirstLevelRepository;
import org.springframework.boot.WebApplicationType;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ComponentScan;

/**
 * Repository启动类
 * @author gaorj
 * @since 2018/10/16
 */
//扫描bean目录
@ComponentScan(value ="com.imooc.springbootautoconfigure.repository")
public class RepositoryBootstrap {

    public static void main(String[] args) {
        //springboot上下文初始化
        ConfigurableApplicationContext context = new SpringApplicationBuilder(RepositoryBootstrap.class)
                //非web工程
                .web(WebApplicationType.NONE)
                .run(args);
        //myFirstLevelRepository bean是否存在
        MyFirstLevelRepository myFirstLevelRepository = context.getBean("myFirstLevelRepository", MyFirstLevelRepository.class);

        System.out.println("myFirstLevelRepository"+myFirstLevelRepository);


        //关闭上下文
        context.close();
    }
}

Spring @Enable 模块装配

Spring Framework 3.1 开始支持”@Enable 模块驱动“。所谓“模块”是指具有相同领域的功能组件集合，组合所造成一个独立的单元。所谓模块是为了实现一个功能所涉及到的各个组件的集合。好比 Web MVC 模块、AspectJ代理模块、Caching（缓存）模块、JMX（Java 管理扩展）模块、Async（异步处理）模块等。

2-4 @Enable 模块装配两种方式

`@Enable` 注解模块举例

框架实现	@Enable 注解模块	激活模块
Spring Framework	@EnableWebMvc	Web MVC 模块
	@EnableTransactionManagement	事务管理模块
	@EnableCaching	Caching 模块
	@EnableMBeanExport	JMX 模块
	@EnableAsync	异步处理模块
	EnableWebFlux	Web Flux 模块
	@EnableAspectJAutoProxy	AspectJ 代理模块
Spring Boot	@EnableAutoConfiguration	自动装配模块
	@EnableManagementContext	Actuator 管理模块
	@EnableConfigurationProperties	配置属性绑定模块
	@EnableOAuth2Sso	OAuth2 单点登陆模块
Spring Cloud	@EnableEurekaServer	Eureka服务器模块
	@EnableConfigServer	配置服务器模块
	@EnableFeignClients	Feign客户端模块
	@EnableZuulProxy	服务网关 Zuul 模块
	@EnableCircuitBreaker	服务熔断模块

实现方式

注解驱动方式

经过引入@Import一个被@configuration模式注解的类来实现此模块的功能，加载相应的bean。

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(DelegatingWebMvcConfiguration.class)
public @interface EnableWebMvc {
}

@Configuration
public class DelegatingWebMvcConfiguration extends
WebMvcConfigurationSupport {
...
}

接口编程方式

引入@Import的类必须实现ImportSelector接口，此接口可以返回多个配置bean，根据注解配置的签名信息决定引入bean，从而实现模块装配的多样化。

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(CachingConfigurationSelector.class)
public @interface EnableCaching {
...
}

public class CachingConfigurationSelector extends AdviceModeImportSelector<EnableCaching> {
/**
* {@inheritDoc}
* @return {@link ProxyCachingConfiguration} or {@code
AspectJCacheConfiguration} for
* {@code PROXY} and {@code ASPECTJ} values of {@link
EnableCaching#mode()}, respectively
*/
public String[] selectImports(AdviceMode adviceMode) {
            switch (adviceMode) {
                case PROXY:
                return new String[] {                AutoProxyRegistrar.class.getName(),ProxyCachingConfiguration.class.getName() };
                case ASPECTJ:
            return new String[] {
        AnnotationConfigUtils.CACHE_ASPECT_CONFIGURATION_CLASS_NAME };
                default:
                return null;
            }
}

ImportSelector接口

package org.springframework.context.annotation;

import org.springframework.core.type.AnnotationMetadata;

/**
 * Interface to be implemented by types that determine which @{@link Configuration}
 * class(es) should be imported based on a given selection criteria, usually one or more
 * annotation attributes.
 *
 * <p>An {@link ImportSelector} may implement any of the following
 * {@link org.springframework.beans.factory.Aware Aware} interfaces, and their respective
 * methods will be called prior to {@link #selectImports}:
 * <ul>
 * <li>{@link org.springframework.context.EnvironmentAware EnvironmentAware}</li>
 * <li>{@link org.springframework.beans.factory.BeanFactoryAware BeanFactoryAware}</li>
 * <li>{@link org.springframework.beans.factory.BeanClassLoaderAware BeanClassLoaderAware}</li>
 * <li>{@link org.springframework.context.ResourceLoaderAware ResourceLoaderAware}</li>
 * </ul>
 *
 * <p>ImportSelectors are usually processed in the same way as regular {@code @Import}
 * annotations, however, it is also possible to defer selection of imports until all
 * {@code @Configuration} classes have been processed (see {@link DeferredImportSelector}
 * for details).
 *
 * @author Chris Beams
 * @since 3.1
 * @see DeferredImportSelector
 * @see Import
 * @see ImportBeanDefinitionRegistrar
 * @see Configuration
 */
public interface ImportSelector {

    /**
     * Select and return the names of which class(es) should be imported based on
     * the {@link AnnotationMetadata} of the importing @{@link Configuration} class.
     */
    String[] selectImports(AnnotationMetadata importingClassMetadata);

}

自定义 `@Enable` 模块

基于注解驱动实现 - @EnableHelloWorld

HelloWorldConfiguration -> HelloWorld
自定义@EnableHelloWorld注解

package com.imooc.springbootautoconfigure.annotation;

import com.imooc.springbootautoconfigure.configuration.HelloWorldConfiguration;
import org.springframework.context.annotation.Import;

import java.lang.annotation.*;

/**
 * @author gaorj
 * @since 2018/10/16
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
//@Import(HelloWorldConfiguration.class)//注解驱动实现方式
@Import(HelloWorldImportSelector.class)//接口编程实现方式
public @interface EnableHelloWorld {
}

基于@Configuration注解import引入的配置类

package com.imooc.springbootautoconfigure.configuration;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

/**
 * @author gaorj
 * @since 2018/10/16
 */
@Configuration
public class HelloWorldConfiguration {

    @Bean
    public String helloWorld() { // 方法名即 Bean 名称
        return "Hello,World 2018";
    }
}

基于接口驱动实现 - @EnableServer

HelloWorldImportSelector -> HelloWorldConfiguration -> HelloWorld
基于实现ImportSelector接口import引入的配置类

package com.imooc.springbootautoconfigure.annotation;

import com.imooc.springbootautoconfigure.configuration.HelloWorldConfiguration;
import org.springframework.context.annotation.ImportSelector;
import org.springframework.core.type.AnnotationMetadata;

/**
 * @author gaorj
 * @since 2018/10/16
 */
public class HelloWorldImportSelector implements ImportSelector {
    @Override
    public String[] selectImports(AnnotationMetadata importingClassMetadata) {
        return new String[]{HelloWorldConfiguration.class.getName()};
    }
}

验证@EnableHelloWorld启动类

package com.imooc.springbootautoconfigure.bootstrap;

import com.imooc.springbootautoconfigure.annotation.EnableHelloWorld;
import org.springframework.boot.WebApplicationType;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.context.ConfigurableApplicationContext;

/**
 * @author gaorj
 * @since 2018/10/16
 */
@EnableHelloWorld
public class EnableHelloWorldBootstrap {
    public static void main(String[] args) {
        ConfigurableApplicationContext context = new SpringApplicationBuilder(EnableHelloWorldBootstrap.class)
                .web(WebApplicationType.NONE)
                .run(args);

        // helloWorld Bean 是否存在
        String helloWorld =
                context.getBean("helloWorld", String.class);

        System.out.println("helloWorld Bean : " + helloWorld);

        // 关闭上下文
        context.close();

    }
}

两种实现方式对比，接口驱动实现因为中间通过ImportSelector转换，此种方式相比注解驱动实现更有弹性，可以实现bean加载方式的多样化，自定义实现多种返回值，相似于条件装配。

Spring 条件装配

2-5 Spring条件装配

从 Spring Framework 3.1 开始，容许在 Bean 装配时增长前置条件判断

条件注解举例

Spring 注解	场景说明	起始版本
@Profile	配置化条件装配	3.1
@Conditional	编程条件装配	4.0

profile参数配置方式有局限，conditional自定义编程更大的灵活性

实现方式

配置方式 - @Profile

@profile注解其实是经过@conditional注解实现的

@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional(ProfileCondition.class)
public @interface Profile {

    /**
     * The set of profiles for which the annotated component should be registered.
     */
    String[] value();

}

编程方式 - @Conditional

@Conditional 注解的定义及其使用，必须配合Condition接口使用。
判断@Conditional注解的签名类OnClassCondition.class是否在当前classpath下存在。
OnClassCondition.class这个类必须实现Condition接口，在此类中根据 @ConditionalOnClass注解的签名信息做匹配判断，是否装配此bean。

/**
 * {@link Conditional} that only matches when the specified classes are on the classpath.
 *
 * @author Phillip Webb
 */
@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional(OnClassCondition.class)
public @interface ConditionalOnClass {

    /**
     * The classes that must be present. Since this annotation is parsed by loading class
     * bytecode, it is safe to specify classes here that may ultimately not be on the
     * classpath, only if this annotation is directly on the affected component and
     * <b>not</b> if this annotation is used as a composed, meta-annotation. In order to
     * use this annotation as a meta-annotation, only use the {@link #name} attribute.
     * @return the classes that must be present
     */
    Class<?>[] value() default {};

    /**
     * The classes names that must be present.
     * @return the class names that must be present.
     */
    String[] name() default {};

}

@Conditional注解的定义

@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Conditional {

    /**
     * All {@link Condition}s that must {@linkplain Condition#matches match}
     * in order for the component to be registered.
     */
    Class<? extends Condition>[] value();

}

Condition接口

public interface Condition {

   /**
    * Determine if the condition matches.
    * @param context the condition context
    * @param metadata metadata of the {@link org.springframework.core.type.AnnotationMetadata class}
    * or {@link org.springframework.core.type.MethodMetadata method} being checked.
    * @return {@code true} if the condition matches and the component can be registered
    * or {@code false} to veto registration.
    */
   boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata);

}

2-6 基于配置方式实现自定义条件装配

自定义条件装配

基于配置方式实现 - @Profile

计算服务，多整数求和：sum
@Profile("Java7") : for 循环
@Profile("Java8") : Lambda
CalculateService求和接口

package com.imooc.springbootautoconfigure.service;

/**
 * @author gaorj
 * @since 2018/10/16
 */
public interface CalculateService {

    /**
     * 从多个整数 sum 求和
     * @param values 多个整数
     * @return sum 累加值
     */
    Integer sum(Integer... values);

}

CalculateService求和接口java7实现

package com.imooc.springbootautoconfigure.service;

import org.springframework.context.annotation.Profile;
import org.springframework.stereotype.Service;

/**
 * @author gaorj
 * @since 2018/10/16
 */
@Service
@Profile("Java7")
public class Java7CalculateService implements CalculateService {
    @Override
    public Integer sum(Integer... values) {
        System.out.println("Java 7 for 循环实现 ");
        int sum = 0;
        for (int i = 0; i < values.length; i++) {
            sum += values[i];
        }
        return sum;
    }

    public static void main(String[] args) {
        CalculateService calculateService = new Java7CalculateService();
        System.out.println(calculateService.sum(1,2,3,4,5,6,7,8,9,10));
    }
}

CalculateService求和接口java8实现

package com.imooc.springbootautoconfigure.service;

import org.springframework.context.annotation.Profile;
import org.springframework.stereotype.Service;

import java.util.stream.Stream;

/**
 * @author gaorj
 * @since 2018/10/16
 */
@Service
@Profile("Java8")//条件配置装配
public class Java8CalculateService implements CalculateService{
    @Override
    public Integer sum(Integer... values) {
        System.out.println("Java 8 Lambda 实现");
        //Integer sum = Stream.of(values).reduce(0, (integer1, integer2) -> integer1 + integer2);
        int sum = Stream.of(values).reduce(0, Integer::sum);
        return sum;
    }

    public static void main(String[] args) {
        CalculateService calculateService = new Java8CalculateService();
        System.out.println(calculateService.sum(1, 2, 3, 4, 5, 6, 7, 8, 9, 10));
    }
}

@Profile启动类验证

package com.imooc.springbootautoconfigure.bootstrap;

import com.imooc.springbootautoconfigure.service.CalculateService;
import org.springframework.boot.WebApplicationType;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.context.ConfigurableApplicationContext;

/**
 * @author gaorj
 * @since 2018/10/16
 */
@SpringBootApplication(scanBasePackages ="com.imooc.springbootautoconfigure.service")
public class CalculateServiceBootstrap {
    public static void main(String[] args) {
        ConfigurableApplicationContext context = new SpringApplicationBuilder(CalculateServiceBootstrap.class).web(WebApplicationType.NONE)
                .profiles("Java7")
                .run(args);

        // CalculateService Bean 是否存在
        CalculateService calculateService = context.getBean(CalculateService.class);

        System.out.println("calculateService.sum(1...10) : " +
                calculateService.sum(1, 2, 3, 4, 5, 6, 7, 8, 9, 10));

        // 关闭上下文
        context.close();
    }
}

2.走向自动装配

2.走向自动装配

Spring 模式注解装配

2-1 走向自动装配

2-2 Spring Framework 手动装配

[模式注解（Stereotype Annotations)]()

模式注解举例

装配方式

`<context:component-scan>` 方式

@ComponentScan 方式

2-3 Spring Framework手动装配自定义模式注解

自定义模式注解

`@Component` “派生性”

`@Component` “层次性”

Spring @Enable 模块装配

2-4 @Enable 模块装配两种方式

`@Enable` 注解模块举例

实现方式

注解驱动方式

接口编程方式

自定义 `@Enable` 模块

基于注解驱动实现 - @EnableHelloWorld

基于接口驱动实现 - @EnableServer

Spring 条件装配

2-5 Spring条件装配

条件注解举例

实现方式

配置方式 - @Profile

编程方式 - @Conditional

2-6 基于配置方式实现自定义条件装配

自定义条件装配

基于配置方式实现 - @Profile

2-7 基于编程方式实现条件装配

基于编程方式实现 - @ConditionalOnSystemProperty

2.走向自动装配

2.走向自动装配

Spring 模式注解装配

2-1 走向自动装配

2-2 Spring Framework 手动装配

[模式注解（Stereotype Annotations)]()

模式注解举例

装配方式

<context:component-scan> 方式

@ComponentScan 方式

2-3 Spring Framework手动装配自定义模式注解

自定义模式注解

@Component “派生性”

@Component “层次性”

Spring @Enable 模块装配

2-4 @Enable 模块装配两种方式

@Enable 注解模块举例

实现方式

注解驱动方式

接口编程方式

自定义 @Enable 模块

基于注解驱动实现 - @EnableHelloWorld

基于接口驱动实现 - @EnableServer

Spring 条件装配

2-5 Spring条件装配

条件注解举例

实现方式

配置方式 - @Profile

编程方式 - @Conditional

2-6 基于配置方式实现自定义条件装配

自定义条件装配

基于配置方式实现 - @Profile

2-7 基于编程方式实现条件装配

基于编程方式实现 - @ConditionalOnSystemProperty

`<context:component-scan>` 方式

`@Component` “派生性”

`@Component` “层次性”

`@Enable` 注解模块举例

自定义 `@Enable` 模块