Spring通過(guò)Java配置集成Tomcat的方法

更新時(shí)間：2021年04月14日 11:11:52 作者：面試官認(rèn)為我什么都會(huì)

這篇文章主要介紹了Spring通過(guò)Java配置集成Tomcat的方法,本文通過(guò)實(shí)例代碼給大家介紹的非常詳細(xì)，對(duì)大家的學(xué)習(xí)或工作具有一定的參考借鑒價(jià)值，需要的朋友可以參考下

添加Tomcat依賴

<!-- 自己編譯的版本-->
<dependency>
    <groupId>org.apache</groupId>
    <artifactId>apache-tomcat-9.0.36-src</artifactId>
    <version>1.0-SNAPSHOT</version>
</dependency>

首先需要一個(gè)tomcat啟動(dòng)類

public class TomcatRun {

	private static final int PORT = 8080;
	private static final String CONTEXT_PATH = "/com/yu";

	public static void main(String[] args) {
		Tomcat tomcat = new Tomcat();
    // 設(shè)置監(jiān)聽(tīng)端口
		tomcat.setPort(PORT);
		tomcat.getHost().setAppBase(".");
    // 這里 Connector 不存在，自動(dòng)創(chuàng)建一個(gè) Connector，并將 tomcat 的端口賦值給 Connector
		tomcat.getConnector();
		tomcat.addWebapp(CONTEXT_PATH, new File("src/main/webapp").getAbsolutePath());
		try {
			tomcat.start();
		} catch (LifecycleException e) {
			e.printStackTrace();
		}
		tomcat.getServer().await();
	}
}

也可以自己創(chuàng)建一個(gè)Connector指定端口

// 手動(dòng)創(chuàng)建 connector
// Connector connector = new Connector();
// connector.setPort(PORT);
// tomcat.getService().addConnector(connector);

創(chuàng)建Spring配置

public class MyWebApplicationInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {
	@Override
	protected Class<?>[] getRootConfigClasses() {
		return new Class[]{RootConfig.class};
	}

	@Override
	protected Class<?>[] getServletConfigClasses() {
		return new Class[]{AppConfig.class};
	}

	@Override
	protected String[] getServletMappings() {
		return new String[]{"/*"};
	}

	@Override
	protected Filter[] getServletFilters() {
		return new Filter[]{
				//
				new CharacterEncodingFilter(StandardCharsets.UTF_8.name())
		};
	}
}

這里就結(jié)束了。。。

問(wèn)題來(lái)了Tomcat是怎么啟動(dòng)Sping的?

實(shí)現(xiàn)了Servlet3.0的容器（例如Tomcat）會(huì)掃描classpath*下面的META-INF/services/javax.servlet.ServletContainerInitializer文件，里面指定ServletContainerInitializer的實(shí)現(xiàn)，另外還有一個(gè)注解HandlesTypes表達(dá)對(duì)某個(gè)類感興趣，在調(diào)用onStartup方法時(shí)會(huì)將HandlesTypes指定接口的實(shí)現(xiàn)類傳遞進(jìn)來(lái)。

例如：Spring中的ServletContainerInitializer實(shí)現(xiàn)類SpringServletContainerInitializer會(huì)調(diào)用WebApplicationInitializer的onStartup方法，也就是上面定義的MyWebApplicationInitializer父類的onStartup，這里就會(huì)相繼完成AnnotationConfigWebApplicationContext和DispatcherServlet的初始化

@HandlesTypes(WebApplicationInitializer.class)
public class SpringServletContainerInitializer implements ServletContainerInitializer {

	@Override
	public void onStartup(@Nullable Set<Class<?>> webAppInitializerClasses, ServletContext servletContext)
			throws ServletException {

		List<WebApplicationInitializer> initializers = new LinkedList<>();

		if (webAppInitializerClasses != null) {
			for (Class<?> waiClass : webAppInitializerClasses) {
				// Be defensive: Some servlet containers provide us with invalid classes,
				// no matter what @HandlesTypes says...
				if (!waiClass.isInterface() && !Modifier.isAbstract(waiClass.getModifiers()) &&
						WebApplicationInitializer.class.isAssignableFrom(waiClass)) {
					try {
						initializers.add((WebApplicationInitializer)
								ReflectionUtils.accessibleConstructor(waiClass).newInstance());
					}
					catch (Throwable ex) {
						throw new ServletException("Failed to instantiate WebApplicationInitializer class", ex);
					}
				}
			}
		}

		if (initializers.isEmpty()) {
			servletContext.log("No Spring WebApplicationInitializer types detected on classpath");
			return;
		}

		servletContext.log(initializers.size() + " Spring WebApplicationInitializers detected on classpath");
		AnnotationAwareOrderComparator.sort(initializers);
		for (WebApplicationInitializer initializer : initializers) {
      // 調(diào)用WebApplicationInitializer實(shí)現(xiàn)類的onStartup方法
			initializer.onStartup(servletContext);
		}
	}

}