如何在Spring Boot中自定义starter

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创建一个用maven构建的springboot项目

pom文件配置如下：

<?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.xjw.springboot</groupId>   <artifactId>hellostarter</artifactId>   <version>0.0.1-SNAPSHOT</version>   <packaging>jar</packaging>   <name>hello-spring-boot-starter</name>   <description>测试自定义starter</description>   <parent>     <groupId>org.springframework.boot</groupId>     <artifactId>spring-boot-starter-parent</artifactId>     <version>1.5.2.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</artifactId>     </dependency>     <dependency>       <groupId>org.springframework.boot</groupId>       <artifactId>spring-boot-starter-test</artifactId>       <scope>test</scope>     </dependency>     <dependency>       <groupId>org.springframework.boot</groupId>       <artifactId>spring-boot-configuration-processor</artifactId>       <optional>true</optional>     </dependency>   </dependencies>   <build>     <plugins>       <plugin>         <groupId>org.springframework.boot</groupId>         <artifactId>spring-boot-maven-plugin</artifactId>       </plugin>     </plugins>   </build> </project>

定义一个pojo用来接收properties中配置的信息

package com.xjw;                                                                                                                    import org.springframework.boot.context.properties.ConfigurationProperties;                                                                                       @ConfigurationProperties(prefix = "hello")                                         public class HelloServiceProperteis {                                                                                                            private String msg;                                                                                                                   public String getMsg() {                                                    return msg;                                                       }                                                                                                                            public void setMsg(String msg) {                                                this.msg = msg;                                                     }                                                                                                                          }

@ConfigurationProperties：用来标识这个pojo是一个用来接收指定前缀的资源配置值

prefix：表示在配置文件中配置项前缀[/code]

编写一个Service用来对外提供服务

package com.xjw; public class HelloService {   private String msg;   public String sayHello() {     return "Hello " + msg;   }   public String getMsg() {     return msg;   }   public void setMsg(String msg) {     this.msg = msg;   } }

配置一个pojo用来读取上面配置的HelloServiceProperteis

package com.xjw;                                                                                                                                      import org.springframework.beans.factory.annotation.Autowired;                                        import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;                                  import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;                               import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;                                import org.springframework.boot.context.properties.EnableConfigurationProperties;                               import org.springframework.context.annotation.Bean;                                              import org.springframework.context.annotation.Configuration;                                                                                                                @Configuration                                                                @EnableConfigurationProperties(value = HelloServiceProperteis.class)                                     @ConditionalOnClass(HelloService.class)                                                    @ConditionalOnProperty(prefix = "hello", value = "enable", matchIfMissing = true)                               public class HelloAutoConfiguration {                                                                                                                              @Autowired                                                                  private HelloServiceProperteis helloServiceProperteis;                                                                                                                   @Bean                                                                     @ConditionalOnMissingBean(HelloService.class)                                                 public HelloService helloService() {                                                       HelloService helloService = new HelloService();                                                helloService.setMsg(helloServiceProperteis.getMsg());                                             return helloService;                                                           }                                                                     }

@Configuration：标识此类为一个spring配置类

@EnableConfigurationProperties(value = HelloServiceProperteis.class):启动配置文件，value用来指定我们要启用的配置类，可以有多个，多个时我们可以这么写value={xxProperties1.class,xxProperteis2.class....}

@ConditionalOnClass(HelloService.class):表示当classPath下存在HelloService.class文件时改配置文件类才有效

@ConditionalOnProperty(prefix = "hello", value = "enable", matchIfMissing = true):表示只有我们的配置文件是否配置了以hello为前缀的资源项值，并且在该资源项值为enable，如果没有配置我们默认设置为enable[/code]

最后在src/main/resources 文件夹下新建文件夹 META-INF，在新建的META-INF文件夹下新建spring.factories

在新建的spring.factories文件中配置自动启动类为我们之前编写的HelloAutoConfiguration 类

org.springframework.boot.autoconfigure.EnableAutoConfiguration=com.xjw.HelloAutoConfiguration

然后就可以在其他的spring-boot项目中使用我们刚刚新建的starter了,我们来测试一下

在新建一个spring-boot项目，pom.xml配置如下:

<?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.xjw.springboot</groupId>   <artifactId>hellostarter.test</artifactId>   <version>0.0.1-SNAPSHOT</version>   <packaging>jar</packaging>   <name>hello-spring-boot-starter-test</name>   <description>测试自定义starter</description>   <parent>     <groupId>org.springframework.boot</groupId>     <artifactId>spring-boot-starter-parent</artifactId>     <version>1.5.2.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>     <dependency>       <groupId>org.springframework.boot</groupId>       <artifactId>spring-boot-starter-test</artifactId>       <scope>test</scope>     </dependency>     <dependency>       <groupId>com.xjw.springboot</groupId>       <artifactId>hellostarter</artifactId>       <version>0.0.1-SNAPSHOT</version>     </dependency>     <dependency>       <groupId>org.springframework.boot</groupId>       <artifactId>spring-boot-devtools</artifactId>     </dependency>   </dependencies>   <build>     <plugins>       <plugin>         <groupId>org.springframework.boot</groupId>         <artifactId>spring-boot-maven-plugin</artifactId>       </plugin>     </plugins>   </build> </project>

然后我们直接在咋们的启动类中中尝试使用以下我们上面定义的starter提供的HelloService:

package com.xjw; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; @RestController @SpringBootApplication public class HelloSpringBootStarterTestApplication {   @Autowired   private HelloService helloService;   @RequestMapping("/")   public String index() {     return helloService.sayHello();   }   public static void main(String[] args) {     SpringApplication.run(HelloSpringBootStarterTestApplication.class, args);   } }

接着我们修改测试项目中的application.properteis，加入如下配置：

debug=true server.port=8888 #hello=enable hello.msg=测试starter

最后启动项目，观察控制台输出的内容中依赖的starter,从Positive matches下我们可以看到有这么一句：

HelloAutoConfiguration matched:
- @ConditionalOnClass found required class 'com.xjw.HelloService'; @ConditionalOnMissingClass did not find unwanted class (OnClassCondition)
- @ConditionalOnProperty (hello.enable) matched (OnPropertyCondition)

或者我们打开项目依赖树也能找到我们的starter ,这说明spring已经自动的启动了我们的starter了，打开浏览器输入地址：http://localhost:8888/将会看到如下结果

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