spring boot 自定义starter的实现教程

2019-11-26 10:41:50

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spring boot 使用 starter 解决了很多配置问题, 但是, 他是怎么来解决这些问题的呢?

这里通过一个简单的例子, 来看一下, starter是怎么来设置默认配置的.

一. 建 starter 项目

自定义的starter, 项目命名规范是：自定义名-spring-boot-starter

先来看一下, 我最后的目录结构

1. 修改pom.xml文件

<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>org.elvin</groupId> <artifactId>my-spring-boot-starter</artifactId> <version>1.0-SNAPSHOT</version> <packaging>jar</packaging> <name>my-spring-boot-starter</name> <url>http://maven.apache.org</url> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-autoconfigure</artifactId> <version>1.5.9.RELEASE</version> </dependency> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>3.8.1</version> <scope>test</scope> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <version>2.3.2</version> <configuration>  <source>1.8</source>  <target>1.8</target> </configuration> </plugin> </plugins> </build></project>

其实只是加入了 spring-boot-autoconfigure

App文件中的main方法, 我注释掉了, 这个在这里没有用到

2. 配置属性对应的接收文件

package org.elvin;import org.springframework.boot.context.properties.ConfigurationProperties;/** * author: Elvin * Date: 2017/12/12 14:51 * Description: */@ConfigurationProperties(prefix = "hello")public class HelloServiceProperties { //默认配置内容 private static final String MSG = "world"; private String msg = MSG; public String getMsg() { return msg; } public void setMsg(String msg) { this.msg = msg; }}

3. 对外Service

package org.elvin;/** * author: Elvin * Date: 2017/12/12 14:55 * Description: */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; }}

4. 对外service与配置对应文件关联

package org.elvin;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;/** * author: Elvin * Date: 2017/12/12 14:59 * Description: */@Configuration@EnableConfigurationProperties(HelloServiceProperties.class)@ConditionalOnClass(HelloService.class)@ConditionalOnProperty(prefix = "hello", value="enabled", matchIfMissing =true )public class HelloServiceAutoConfiguration { @Autowired private HelloServiceProperties helloServiceProperties; @Bean @ConditionalOnMissingBean(HelloService.class) public HelloService helloService(){ HelloService helloService = new HelloService(); helloService.setMsg(helloServiceProperties.getMsg()); return helloService; }}

5. starter配置 : spring.factories

org.springframework.boot.autoconfigure.EnableAutoConfiguration=org.elvin.HelloServiceAutoConfiguration

做完这些之后, 通过 mvn clean install , 打包到maven库里面

二. spring boot 项目使用

新建一个spring boot 项目, 选择web即可.

目录结构：

先看一下引用pom.xml

<dependency>   <groupId>org.elvin</groupId>   <artifactId>my-spring-boot-starter</artifactId>   <version>1.0-SNAPSHOT</version>  </dependency>

再看一下HelloController

package org.elvin.learn.springboot.controller;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RestController;import org.elvin.*;/** * author: Elvin * Date: 2017/12/12 15:34 * Description: */@RestController@RequestMapping("hello")public class HelloController { @Autowired private HelloService helloService; @RequestMapping("index") public String index(){  return helloService.sayHello(); }}

这里的 HelloService 就是前面自定义 starter 里面的.

1. 结果: 未配置情况下, 应该是输出 hello world