Spring 注解驱动设计模式-组团学

1、Spring @Enable模块驱动概述

Spring Framework3.1 是一个其有里程碑意义的发行版本,从此版本开始,Spring Framework开始支持"@Enable模块驱动"。所谓"模块"是指具备相同领域的功能组件集合,例如Web MVC模块、AspectJ模块等。

2、理解@Enable模块驱动

@Enable模块驱动在后续的Spring Framework、Spring Boot和Spring Cloud中一以贯之,这种模块化的Annotation均以@Enable作为前缀，例如:@EnableWebFlux、@EnableWebMVC等。@Enable模块驱动的意义在于简化装配步骤,实现"按需装配",同时屏蔽组件集合装配的细节。

查看@EnableWebFlux注解

@Retention(RetentionPolicy.RUNTIME) //元注解，表示注解不仅保存在class文件，并且jvm加载class文件之后，仍然存在
@Target({ElementType.TYPE}) //表示此注解的标识范围为接口、类、枚举
@Documented //表示该注解会被javadoc工具记录
@Import({DelegatingWebFluxConfiguration.class}) //通过快速导入的方式实现把实例加入spring的IOC容器中
public @interface EnableWebFlux {
}
@Configuration(
    proxyBeanMethods = false
)
public class DelegatingWebFluxConfiguration extends WebFluxConfigurationSupport {

3、自定义@Enable模块驱动

3.1、创建maven工程

pom.xml内容如下:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.tyschool</groupId>
    <artifactId>enable-driver</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <!-- Spring 3.x 最新发布版本 -->
        <spring.version>3.2.18.RELEASE</spring.version>
        <java.version>1.9</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${spring.version}</version>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>${java.version}</source>
                    <target>${java.version}</target>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

3.2、实现Configuration类

@Configuration
public class HelloConfig {

    /***
     * 创建名为"helloWorld"String类型的Bean
     * @return
     */
    @Bean
    public String helloWorld(){
        return "Hello,World";
    }
}

3.3、实现"@Enable模块驱动"注解

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

3.4、标注@EnableHello到引到类

@EnableHello
@Configuration
public class EnableHelloBootStrap {

    public static void main(String[] args) {
        //构建Annotation配置驱动Spring上下文
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
        //注册当前引导类到Spring上下文
        context.register(EnableHelloBootStrap.class);
        //启动上下文
        context.refresh();
        //获取名称为"helloWorld"的Bean对象
        String helloWorld = context.getBean("helloWorld", String.class);
        //输出
        System.out.println(helloWorld);
        //关闭上下文
        context.close();
    }

4、Spring Web自动装配概述

Spring Framwork 3.1.0.RELEASE中新引入的WebApplicationInitializer构建在Servlet3.0 之上,应用在Servlet3.0+的环境也可以采用编程手段实现。

WebApplicationInitializer属于Spring MVC提供的接口,确保Web ApplicationInitializer自定义实现能够被任何Servlet3.0容器侦测并自动地初始化。如果实现WebApplicationInitializer接口较为困难,也可使用简化实现方案，即AbstractDispatcherServletInitializer。

AbstractAnnotaionConfigDispatcherServletInitializer是AbstactDispatcherServletInitializer的子类。前者实现属于Spring Java代码配置驱动,后者实现是Spring XML配置驱动。

5、自定义Web自动装配

5.1、在pom.xml文件中添加web依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <packaging>war</packaging>
    <groupId>com.tyschool</groupId>
    <artifactId>enable-driver</artifactId>
    <version>1.0-SNAPSHOT</version>
    <properties>
        <!-- Spring 3.x 最新发布版本 -->
        <spring.version>3.2.18.RELEASE</spring.version>
        <java.version>1.9</java.version>
    </properties>
    <dependencies>
        <!-- Servlet 3.0 API -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.0.1</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.apache.tomcat.maven</groupId>
            <artifactId>tomcat7-maven-plugin</artifactId>
            <version>2.1</version>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <!-- Spring Web MVC 依赖 -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${spring.version}</version>
        </dependency>
    </dependencies>
    <build>
        <plugins>

            <!-- Maven war 插件 -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <configuration>
                    <!-- 忽略错误，当web.xml不存在时 -->
                    <failOnMissingWebXml>false</failOnMissingWebXml>
                </configuration>
            </plugin>

            <!-- Tomcat Maven 插件用于构建可执行 war -->
            <plugin>
                <groupId>org.apache.tomcat.maven</groupId>
                <artifactId>tomcat7-maven-plugin</artifactId>
                <version>2.1</version>
                <executions>
                    <execution>
                        <id>tomcat-run</id>
                        <goals>
                            <!-- 最终打包成可执行的jar包 -->
                            <goal>exec-war-only</goal>
                        </goals>
                        <phase>package</phase>
                        <configuration>
                            <!-- ServletContext 路径 -->
                            <path>/</path>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

        </plugins>
    </build>
</project>

5.2、新增@Controller

@Controller //标识为controller
public class HelloWorldController {
    
    @RequestMapping("/hello")
    @ResponseBody //返回json数据格式
    public String helloWorld(){
        return "Hello,World!";
    }
}

5.3、新增Spring Web MVC配置

@EnableWebMvc //开启WebMvc
@Configuration //标识为配置类
@ComponentScan(basePackageClasses = SpringWebMvcConfiguration.class)//扫描SpringWebMvcConfiguration所在的包及子包
public class SpringWebMvcConfiguration {
    
}

5.4、实现AbstractAnnotationConfigDispatcherServletInitializer

package com.tyschool.initializer;

import com.tyschool.config.SpringWebMvcConfiguration;
import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;

public class SpringWebMvcServletInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {

    protected Class<?>[] getRootConfigClasses() {
        return new Class[0];
    }

    //DispatcherServlet配置Bean
    protected Class<?>[] getServletConfigClasses() {
        return of(SpringWebMvcConfiguration.class);
    }


    //DispathcerServlet URL Pattern映射
    protected String[] getServletMappings() {
        return of("/*");
    }


    private static <T> T [] of(T... values) {
        return values;
    }
}

5.5、打包并运行

java -jar enable-driver-1.0-SNAPSHOT-war-exec.jar

Spring 注解驱动设计模式