SpringBoot源码阅读--自定义Starter
新建一个maven项目，引入相关依赖。然后在META-INF文件夹下新建文件 spring.factories。配置我们的自动配置类
org.springframework.boot
spring-boot-starter-parent
2.1.5.RELEASE
4.0.0
com.itw.boot
my-boot-study-starter
org.springframework.boot
spring-boot-starter-web
org.springframework.boot
spring-boot-starter-test
org.projectlombok
lombok
com.alibaba
fastjson
1.2.45
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.itw.autoConfig.AutoConfigWeatherPropertiespackage com.itw.autoConfig;
import com.itw.configProperties.WeatherProperties;
import com.itw.service.WeatherService;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;
//我们的注解@Configuration，表明这是个配置类
//EnableConfigurationProperties注解配合注解@ConfigurationProperties使用，自动注入
@Configuration
@EnableConfigurationProperties(WeatherProperties.class)
public class AutoConfigWeatherProperties {
@Bean
public RestTemplate getRestTemplate (){
return new RestTemplate();
}
@Bean
public WeatherService getWeatherService(WeatherProperties weatherProperties){
return new WeatherService(weatherProperties);
}
}
package com.itw.configProperties;
import lombok.Data;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.validation.annotation.Validated;
import javax.validation.constraints.NotNull;
@Data
@ConfigurationProperties(prefix = "myapp.weather")
@Validated
public class WeatherProperties {
@NotNull
String urlStr;
@NotNull
String appKey;
}
package com.itw.service;
import com.itw.configProperties.WeatherProperties;
import net.minidev.json.JSONObject;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.web.client.RestTemplate;
public class WeatherService {
@Autowired
private RestTemplate restTemplate;
public WeatherService(WeatherProperties weatherProperties) {
this.appKey = weatherProperties.getAppKey();
this.urlStr = weatherProperties.getUrlStr();
}
private String urlStr;
private String appKey;
public String getWeatherInfo(String city){
JSONObject jsonObject = new JSONObject();
jsonObject.put("appkey", appKey);
jsonObject.put("city", city);
String json = JSONObject.toJSONString(jsonObject);
//使用restTemplate进行访问远程Http服务
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON_UTF8);
HttpEntity httpEntity = new HttpEntity(json, headers);
//这个接口的appkey不能放到请求体中，所以需要修改逻辑
String result = restTemplate.postForObject(urlStr, httpEntity, String.class);
return result;
}
}
然后，打包之后就可以，供其他模块或项目引用了。
package com.itwzhangzx.boot.controller;
import com.itw.service.WeatherService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import javax.servlet.http.HttpServletRequest;
@RestController
public class WeatherController {
//别的项目中直接使用我们之前的starter中的对象
@Autowired
private WeatherService weatherService;
@RequestMapping("/getWeatherByCity")
public String getWeatherByCity(HttpServletRequest request){
return weatherService.getWeatherInfo(request.getParameter("city"));
}
}
为啥我们的项目中能直接用jar包中的对象，关键就在于注解：
@EnableAutoConfigurationpackage org.springframework.boot.autoconfigure;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage
@Import(AutoConfigurationImportSelector.class)
public @interface EnableAutoConfiguration {
//省略。。。
}
我们先看new我们的实例SpringApplication对象的步骤：
public SpringApplication(ResourceLoader resourceLoader, Class... primarySources) {
this.resourceLoader = resourceLoader;
Assert.notNull(primarySources, "PrimarySources must not be null");
this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
//判断我们的应用类型，这儿我们时web服务 SERVLET
this.webApplicationType = WebApplicationType.deduceFromClasspath();
//加载ApplicationContextInitializer 容器初始化器（）
//从类路径下找到META-INF/spring.factories配置的所有ApplicationContextInitializer
setInitializers((Collection) getSpringFactoriesInstances(
ApplicationContextInitializer.class));
//从类路径下找到META-INF/spring.factories配置的所有ApplicationContextInitializer
setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
//就是找到我们的启动类，比我 MyAppDemo
this.mainApplicationClass = deduceMainApplicationClass();
}然后看我们的run方法：
public ConfigurableApplicationContext run(String... args) {
//一个计时器。用于统计初始化容器时间
StopWatch stopWatch = new StopWatch();
stopWatch.start();
ConfigurableApplicationContext context = null;
Collection exceptionReporters = new ArrayList<>();
//配置模式 java.awt.headless 系统配置，自行百度
configureHeadlessProperty();
//配置我们的监听器 SpringApplicationRunListener
//从类路径下找到META-INF/spring.factories配置的所有SpringApplicationRunListener
SpringApplicationRunListeners listeners = getRunListeners(args);
//回调监听器的starting方法，监听器是排好序的，这儿按序执行starting方法
listeners.starting();
try { //main方法的参数，封装
ApplicationArguments applicationArguments = new DefaultApplicationArguments(
args);
//环境中存储我们的所有的配置信息，比如我们的yml文件中的配置参数
ConfigurableEnvironment environment = prepareEnvironment(listeners,
applicationArguments);
//spring.beaninfo.ignore属性的配置
configureIgnoreBeanInfo(environment);
//打印banner
Banner printedBanner = printBanner(environment);
//创建IOC容器
context = createApplicationContext();
exceptionReporters = getSpringFactoriesInstances(
SpringBootExceptionReporter.class,
new Class[] { ConfigurableApplicationContext.class }, context);
prepareContext(context, environment, listeners, applicationArguments,
printedBanner);
//容器中放入我们的bean，configuration，组件，bean的装配
refreshContext(context);
afterRefresh(context, applicationArguments);
stopWatch.stop();
if (this.logStartupInfo) {
new StartupInfoLogger(this.mainApplicationClass)
.logStarted(getApplicationLog(), stopWatch);
}
listeners.started(context);
callRunners(context, applicationArguments);
}
catch (Throwable ex) {
handleRunFailure(context, ex, exceptionReporters, listeners);
throw new IllegalStateException(ex);
}
try {
listeners.running(context);
}
catch (Throwable ex) {
handleRunFailure(context, ex, exceptionReporters, null);
throw new IllegalStateException(ex);
}
return context;
}
我们的配置类，也就是注解@Configuration标识了的类会在刷新容器的时候，初始化，然后放入容器中。