Spring Boot 自定义starter的示例代码

2019-11-26 09:30:58

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SpringBoot 个人感觉特点：

1）众多库的集合（各种Starter），方便快速构建应用系统。

2）自动配置spring（通过AutoConfiguration机制），简化配置，也方便扩展新的Starter。

3）内嵌web容器，无需WAR部署。

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@SpringBootApplicationpublic 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=trueserver.port=8888#hello=enablehello.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