一、简介

SpringBoot 最强大的功能就是把我们常用的场景抽取成了一个个starter(场景启动器),我们通过引入springboot 为我提供的这些场景启动器,我们再进行少量的配置就能使用相应的功能。即使是这样,springboot也不能囊括我们所有的使用场景,往往我们需要自定义starter,来简化我们对springboot的使用。

二、如何自定义starter

1.实例

如何编写自动配置 ?

我们参照@WebMvcAutoConfiguration为例,我们看看们需要准备哪些东西,下面是WebMvcAutoConfiguration的部分代码:

@Configuration@ConditionalOnWebApplication@ConditionalOnClass({Servlet.class, DispatcherServlet.class, WebMvcConfigurerAdapter.class})@ConditionalOnMissingBean({WebMvcConfigurationSupport.class})@AutoConfigureOrder(-2147483638)@AutoConfigureAfter({DispatcherServletAutoConfiguration.class, ValidationAutoConfiguration.class})public class WebMvcAutoConfiguration {

    @Import({WebMvcAutoConfiguration.EnableWebMvcConfiguration.class})
    @EnableConfigurationProperties({WebMvcProperties.class, ResourceProperties.class})
    public static class WebMvcAutoConfigurationAdapter extends WebMvcConfigurerAdapter {

        @Bean
        @ConditionalOnBean({View.class})
        @ConditionalOnMissingBean
        public BeanNameViewResolver beanNameViewResolver() {
            BeanNameViewResolver resolver = new BeanNameViewResolver();
            resolver.setOrder(2147483637);
            return resolver;
        }
    }}

我们可以抽取到我们自定义starter时同样需要的一些配置。

@Configuration  //指定这个类是一个配置类@ConditionalOnXXX  //指定条件成立的情况下自动配置类生效@AutoConfigureOrder  //指定自动配置类的顺序@Bean  //向容器中添加组件@ConfigurationProperties  //结合相关xxxProperties来绑定相关的配置@EnableConfigurationProperties  //让xxxProperties生效加入到容器中自动配置类要能加载需要将自动配置类,配置在META-INF/spring.factories中
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration,\
org.springframework.boot.autoconfigure.aop.AopAutoConfiguration,\

模式

我们参照 spring-boot-starter 我们发现其中没有代码:

1.png


我们在看它的pom中的依赖中有个 springboot-starter

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter</artifactId></dependency>

我们再看看 spring-boot-starter 有个 spring-boot-autoconfigure

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-autoconfigure</artifactId></dependency>

关于web的一些自动配置都写在了这里 ,所以我们有总结:

启动器starter只是用来做依赖管理
需要专门写一个类似spring-boot-autoconfigure的配置模块
用的时候只需要引入启动器starter,就可以使用自动配置了

命名规范

官方命名空间

  • 前缀:spring-boot-starter-

  • 模式:spring-boot-starter-模块名

  • 举例:spring-boot-starter-web、spring-boot-starter-jdbc

自定义命名空间

  • 后缀:-spring-boot-starter

  • 模式:模块-spring-boot-starter

  • 举例:mybatis-spring-boot-starter

三、自定义starter实例

我们需要先创建两个工程 hello-spring-boot-starterhello-spring-boot-starter-autoconfigurer

1. hello-spring-boot-starter

1.pom.xml

<?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.gf</groupId>
    <artifactId>hello-spring-boot-starter</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>hello-spring-boot-starter</name>

    <!-- 启动器 -->
    <dependencies>
        <!-- 引入自动配置模块 -->
        <dependency>
            <groupId>com.gf</groupId>
            <artifactId>hello-spring-boot-starter-autoconfigurer</artifactId>
            <version>0.0.1-SNAPSHOT</version>
        </dependency>
    </dependencies></project>

同时删除 启动类、resources下的文件,test文件。

2. hello-spring-boot-starter-autoconfigurer

1. pom.xml

<?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.gf</groupId>
    <artifactId>hello-spring-boot-starter-autoconfigurer</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>hello-spring-boot-starter-autoconfigurer</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.9.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <!-- 引入spring-boot-starter,所有starter的基本配合 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

    </dependencies></project>

2. HelloProperties

package com.gf.service;import org.springframework.boot.context.properties.ConfigurationProperties;@ConfigurationProperties(prefix = "gf.hello")public class HelloProperties {

    private String prefix;
    private String suffix;

    public String getPrefix() {
        return prefix;
    }

    public void setPrefix(String prefix) {
        this.prefix = prefix;
    }

    public String getSuffix() {
        return suffix;
    }

    public void setSuffix(String suffix) {
        this.suffix = suffix;
    }}

3. HelloService

package com.gf.service;public class HelloService {

    HelloProperties helloProperties;

    public HelloProperties getHelloProperties() {
        return helloProperties;
    }

    public void setHelloProperties(HelloProperties helloProperties) {
        this.helloProperties = helloProperties;
    }

    public String sayHello(String name ) {
        return helloProperties.getPrefix()+ "-" + name + helloProperties.getSuffix();
    }}

4. HelloServiceAutoConfiguration

package com.gf.service;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;import org.springframework.boot.context.properties.EnableConfigurationProperties;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;@Configuration@ConditionalOnWebApplication //web应该生效@EnableConfigurationProperties(HelloProperties.class)public class HelloServiceAutoConfiguration {

    @Autowired
    HelloProperties helloProperties;

    @Bean
    public HelloService helloService() {
        HelloService service = new HelloService();
        service.setHelloProperties( helloProperties  );
        return service;
    }}

5. spring.factories

resources 下创建文件夹 META-INF 并在 META-INF 下创建文件 spring.factories ,内容如下:

# Auto Configure
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.gf.service.HelloServiceAutoConfiguration

到这儿,我们的配置自定义的starter就写完了 ,我们hello-spring-boot-starter-autoconfigurer、hello-spring-boot-starter 安装成本地jar包。

三、测试自定义starter

我们创建个项目 hello-spring-boot-starter-test,来测试系我们写的stater。

1. pom.xml

<?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.gf</groupId>
    <artifactId>hello-spring-boot-starter-test</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>hello-spring-boot-starter-test</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.9.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <!-- 引入自定义starter -->
        <dependency>
            <groupId>com.gf</groupId>
            <artifactId>hello-spring-boot-starter</artifactId>
            <version>0.0.1-SNAPSHOT</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build></project>

2. HelloController

package com.gf.controller;import com.gf.service.HelloService;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.PathVariable;import org.springframework.web.bind.annotation.RestController;@RestControllerpublic class HelloController {

    @Autowired
    HelloService helloService;

    @GetMapping("/hello/{name}")
    public String hello(@PathVariable(value = "name") String name) {
        return helloService.sayHello( name + " , " );
    }}

3. application.properties

gf.hello.prefix = hi
gf.hello.suffix = what's up man ?

我运行项目访问 http://127.0.0.1:8080/hello/zhangsan,结果如下:

hi-zhangsan , what's up man ?

source : https://github.com/gf-huanchupk/SpringBootLearning


转自:https://www.jianshu.com/p/b5794bbd4b54