前言:
现时大家对“前端调用controller”都比较着重,小伙伴们都想要学习一些“前端调用controller”的相关文章。那么小编同时在网络上网罗了一些有关“前端调用controller””的相关知识,希望各位老铁们能喜欢,看官们一起来了解一下吧!1.基本介绍
文档:SpringBoot中注入Servlet&Filter&Listener
考虑到实际开发业务非常复杂和兼容问题,SpringBoot支持将Servlet、Filter、Listener注入spring容器中,成为Spring Bean也就是说,SpringBoot开放了和原生WEB组件(Servlet、Filter、Listener)的兼容SpringBoot注入Servlet、Filter、Listener,有两种方式:通过注解方式注入使用RegistrationBean方式注入2.通过注解方式注入2.1@WebServlet
属性名
对应标签
描述
name
<servlet-name>
指定 Servlet 的 name 属性。 如果没有显式指定,则取值为该 Servlet 的完全限定名,即包名+类名
value
<url-pattern>
该属性等价于 urlPatterns 属性,两者不能同时指定。 如果同时指定,通常是忽略 value 的取值
urlPatterns
<url-pattern>
指定一组 Servlet 的 URL 匹配模式
loadOnStartup
<load-on-startup>
指定 Servlet 的加载顺序
initParams
<init-param>
指定一组 Servlet 初始化参数
asyncSupported
<async-supported>
声明 Servlet 是否支持异步操作模式
description
<description>
指定该 Servlet 的描述信息
displayName
<display-name>
指定该 Servlet 的显示名
例子--使用@WebServlet注入Servlet
(1)MyServlet.java
通过继承HttpServlet来开发原生的Servlet使用@WebServlet,表示将其标识的对象注入到Spring容器中urlPatterns = {"servlet01","servlet02"} 对此servlet配置了映射路径对于开发的原生的Servlet,需要使用@ServletComponentScan在SpringBoot主程序中,指定要扫描的原生Servlet,这样该Servlet才能注入容器
package com.li.thymeleaf.servlet; import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.io.IOException; /** * @author 李 * @version 1.0 */@WebServlet(urlPatterns = {"/servlet01", "/servlet02"})public class MyServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { resp.getWriter().write("Hello,MyServlet!"); }}
(2)Application.java主程序
package com.li.thymeleaf; import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.boot.web.servlet.ServletComponentScan; /** * @author 李 * @version 1.0 *///指定扫描Servlet@ServletComponentScan(basePackages = "com.li.thymeleaf")@SpringBootApplicationpublic class Application { public static void main(String[] args) { SpringApplication.run(Application.class,args); }}
(3)浏览器访问地址:获者,返回如下:
注意:注入的Servlet不会被SpringBoot的拦截器拦截(因为原生Servlet和前端控制器DispatcherServlet是统一级别的,而拦截器在DispatcherServlet中)
2.2@WebFilter
属性名
说 明
description
该过滤器的描述信息,等价于 <description>标签。
displayName
该过滤器的显示名,通常配合工具使用,等价于 <display-name> 标签
initParams
指定一组过滤器初始化参数,等价于 <init-param> 标签。
filterName
指定过滤器的 name 属性,等价于 <filter-name>
servletNames
指定过滤器将应用于哪些 Servlet。取值是 @WebServlet 中的 name 属性的取值,或者是 web.xml 中 <servlet-name> 的取值
value/urlPatterns
过滤器的 URL 匹配模式,等价于<url-pattern>标签
dispatcherTypes
指定过滤器的转发模式。具体取值包括: ASYNC、ERROR、FORWARD、INCLUDE、REQUEST。
asyncSupported
声明过滤器是否支持异步操作模式, 等价于<async-supported>标签
例子--使用@WebFilter注入Filter
@WebFilter标识一个过滤器,并注入spring容器urlPatterns = {"/css/*", "/images/*"}表示请求/css/目录或者/images/目录下的资源时,请求会经过这个过滤器需要在主程序中,指定要扫描的Filter,这样该Filter才能注入容器
package com.li.thymeleaf.filter; import lombok.extern.slf4j.Slf4j; import javax.servlet.*;import javax.servlet.annotation.WebFilter;import javax.servlet.http.HttpServletRequest;import java.io.IOException; /** * @author 李 * @version 1.0 * 开发Filter并注入spring容器 */@Slf4j@WebFilter(urlPatterns = {"/css/*", "/images/*"})public class MyFilter implements Filter { @Override public void init(FilterConfig filterConfig) throws ServletException { log.info("MyFilter的init()方法被执行..."); } @Override public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { log.info("MyFilter的doFilter()方法被执行..."); HttpServletRequest httpServletRequest = (HttpServletRequest) request; log.info("过滤器处理的uri={}", httpServletRequest.getRequestURI()); chain.doFilter(request, response);//放行 } @Override public void destroy() { log.info("MyFilter的destroy()方法被执行..."); }}
(2)在主程序中配置扫描该过滤器(略)
(3)在浏览器访问地址:,后台输出:
2023-03-23 18:59:36.685 INFO 39228 --- [nio-8080-exec-6] com.li.thymeleaf.filter.MyFilter : MyFilter的doFilter()方法被执行...2023-03-23 18:59:36.685 INFO 39228 --- [nio-8080-exec-6] com.li.thymeleaf.filter.MyFilter : 过滤器处理的uri=/images/login.jpg
有时候后台没有输出,可能是浏览器缓存问题
2.3@WebListener
(1)MyListener.java
package com.li.thymeleaf.listener; import lombok.extern.slf4j.Slf4j; import javax.servlet.ServletContextEvent;import javax.servlet.ServletContextListener;import javax.servlet.annotation.WebListener; /** * @author 李 * @version 1.0 */@Slf4j@WebListenerpublic class MyListener implements ServletContextListener { @Override public void contextInitialized(ServletContextEvent sce) { //可以加入项目初始化相关的业务 log.info("MyListener-contextInitialized()-项目初始化OK~"); } @Override public void contextDestroyed(ServletContextEvent sce) { //可以加入业务 log.info("MyListener-contextDestroyed()-项目初销毁..."); }}
(2)在主程序 Application.java配置扫描该监听器
package com.li.thymeleaf; import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.boot.web.servlet.ServletComponentScan;import org.springframework.context.ConfigurableApplicationContext; /** * @author 李 * @version 1.0 *///指定扫描监听器@ServletComponentScan(basePackages = "com.li.thymeleaf")@SpringBootApplicationpublic class Application { public static void main(String[] args) { ConfigurableApplicationContext ioc = SpringApplication.run(Application.class, args); //监听器的contextDestroyed()方法在容器销毁时触发 ioc.stop(); }}
(3)启动项目,控制台输出:
3.使用RegistrationBean方式注入
RegistrationConfig.java:
package com.li.thymeleaf.config; import com.li.thymeleaf.filter.MyFilter;import com.li.thymeleaf.listener.MyListener;import com.li.thymeleaf.servlet.MyServlet;import org.springframework.boot.web.servlet.FilterRegistrationBean;import org.springframework.boot.web.servlet.ServletListenerRegistrationBean;import org.springframework.boot.web.servlet.ServletRegistrationBean;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration; import java.util.Arrays; /** * @author 李 * @version 1.0 * RegistrationConfig是一个配置类, * 默认为单实例模式 proxyBeanMethods=true */@Configurationpublic class RegistrationConfig { //使用RegistrationBean方式注入Servlet @Bean public ServletRegistrationBean servlet_() { MyServlet myServlet = new MyServlet(); //将myServlet关联到ServletRegistrationBean对象 //可以指定多个映射url return new ServletRegistrationBean(myServlet, "/servlet01", "/servlet02"); } //使用RegistrationBean方式注入Filter @Bean public FilterRegistrationBean filter_() { MyFilter myFilter = new MyFilter();//创建原生的Filter对象 FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean(myFilter); //设置filter的urlPattern filterRegistrationBean.setUrlPatterns(Arrays.asList("/css/*", "/images/*")); return filterRegistrationBean; } //使用RegistrationBean方式注入Listener @Bean public ServletListenerRegistrationBean listener_() { MyListener myListener = new MyListener();//创建原生的Listener对象 return new ServletListenerRegistrationBean(myListener); }}
使用RegistrationBean的方式注入,不必在主程序Application.java中配置扫描
运行程序,可以看到三个组件都被注入到容器中:
4.注意事项和细节4.1请求自定义Servlet时,为什么不会到达拦截器?
原因分析:
注入的Servlet会存在Spring容器,DispatcherServlet也存在Spring容器。当多个Servlet都能处理到同一层路径时,存在精确优先原则/最长前缀匹配原则:**精准匹配 > 目录匹配 > 扩展名匹配 > /* > / **
如下图:当浏览器请求路径为/servlet01时,MyServlet的映射路径对与浏览器请求来说是精准匹配,因此此时MyServlet的映射路径优先级高于前端控制器的 /,请求路径会走tomcat流程,不会到达前端控制器,也就不会执行拦截器。
当然,在SpringBoot中,去调用@Controller目标方法,仍是按照DispatcherServlet分发匹配的机制
4.2DispatcherServlet在SpringBoot如何进行配置和注入
DispatcherServletAutoConfiguration 完成对 DispatcherServlet 的自动配置。
DispatcherServletAutoConfiguration 类,有一个内部类:
@Configuration(proxyBeanMethods = false)@Conditional(DefaultDispatcherServletCondition.class)@ConditionalOnClass(ServletRegistration.class)@EnableConfigurationProperties(WebMvcProperties.class)protected static class DispatcherServletConfiguration { @Bean(name = DEFAULT_DISPATCHER_SERVLET_BEAN_NAME) //创建了DispatcherServlet对象,并进行一系列设置并返回。 public DispatcherServlet dispatcherServlet(WebMvcProperties webMvcProperties) { DispatcherServlet dispatcherServlet = new DispatcherServlet(); dispatcherServlet.setDispatchOptionsRequest(webMvcProperties.isDispatchOptionsRequest()); dispatcherServlet.setDispatchTraceRequest(webMvcProperties.isDispatchTraceRequest()); dispatcherServlet.setThrowExceptionIfNoHandlerFound(webMvcProperties.isThrowExceptionIfNoHandlerFound()); dispatcherServlet.setPublishEvents(webMvcProperties.isPublishRequestHandledEvents()); dispatcherServlet.setEnableLoggingRequestDetails(webMvcProperties.isLogRequestDetails()); return dispatcherServlet; } @Bean @ConditionalOnBean(MultipartResolver.class) @ConditionalOnMissingBean(name = DispatcherServlet.MULTIPART_RESOLVER_BEAN_NAME) public MultipartResolver multipartResolver(MultipartResolver resolver) { // Detect if the user has created a MultipartResolver but named it incorrectly return resolver; } }
然后通过如下方法,创建DispatcherServletRegistrationBean对象,并将创建的DispatcherServlet对象关联到这个DispatcherServletRegistrationBean对象中,将DispatcherServletRegistrationBean对象通过@Bean注入到容器中。
@Configuration(proxyBeanMethods = false)@Conditional(DispatcherServletRegistrationCondition.class)@ConditionalOnClass(ServletRegistration.class)@EnableConfigurationProperties(WebMvcProperties.class)@Import(DispatcherServletConfiguration.class)protected static class DispatcherServletRegistrationConfiguration { @Bean(name = DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME) @ConditionalOnBean(value = DispatcherServlet.class, name = DEFAULT_DISPATCHER_SERVLET_BEAN_NAME) public DispatcherServletRegistrationBean dispatcherServletRegistration(DispatcherServlet dispatcherServlet, WebMvcProperties webMvcProperties, ObjectProvider<MultipartConfigElement> multipartConfig) { DispatcherServletRegistrationBean registration = new DispatcherServletRegistrationBean(dispatcherServlet, webMvcProperties.getServlet().getPath());//设置路径 / registration.setName(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME); registration.setLoadOnStartup(webMvcProperties.getServlet().getLoadOnStartup()); multipartConfig.ifAvailable(registration::setMultipartConfig); return registration; } }
标签: #前端调用controller