SpringMVC请求分发的简单实现
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简介
以前用了下SpringMVC感觉挺不错了,前段事件也简单了写了一些代码来实现了SpringMVC简单的请求分发功能,实现的主要思想如下:
- 将处理请求的类在系统启动的时候加载起来,相当于SpringMVC中的Controller
- 读取Controller中的配置并对应其处理的URL
- 通过调度Servlet进行拦截请求,并找到相应的Controller进行处理
主要代码
首先得标识出来哪些类是Controller类,这里我自己定义的是ServletHandler,通过Annotation的方式进行标识,并配置每个类和方法处理的URL:
- package com.meet58.base.servlet.annotation;
- public @interface ServletHandler {
- }
这里注解主要是声明这个类是一个ServletHandler类,用于处理请求的类,系统启动的时候就会加载这些类。
- package com.meet58.base.servlet.annotation;
- import java.lang.annotation.Documented;
- import java.lang.annotation.ElementType;
- import java.lang.annotation.Retention;
- import java.lang.annotation.RetentionPolicy;
- import java.lang.annotation.Target;
- import com.meet58.base.servlet.types.RequestMethod;
- import com.meet58.base.servlet.types.ResponseType;
- @Target({ElementType.TYPE, ElementType.METHOD})
- @Retention(RetentionPolicy.RUNTIME)
- @Documented
- public @interface HandlerMapping {
- String value();
- }
这个注解是配置处理请求的注解,定义了要处理的路径。
定义了注解之后就是要在系统启动的时候扫描并加载这些类,下面是如何进行扫描的代码:
- package com.meet58.base.servlet.mapping;
- import java.io.IOException;
- import org.springframework.core.io.Resource;
- import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
- import org.springframework.core.io.support.ResourcePatternResolver;
- import org.springframework.core.io.support.ResourcePatternUtils;
- import org.springframework.core.type.classreading.CachingMetadataReaderFactory;
- import org.springframework.core.type.classreading.MetadataReader;
- import org.springframework.core.type.classreading.MetadataReaderFactory;
- import org.springframework.core.type.filter.AnnotationTypeFilter;
- import org.springframework.core.type.filter.TypeFilter;
- import org.springframework.util.ClassUtils;
- import com.meet58.base.servlet.annotation.ServletHandler;
- public class ServletHandlerMappingResolver {
- private static final String RESOURCE_PATTERN = "/**/*.class";
- private String[] packagesToScan;
- private ResourcePatternResolver resourcePatternResolver;
- private static final TypeFilter[] ENTITY_TYPE_FILTERS = new TypeFilter[] {
- new AnnotationTypeFilter(ServletHandler.class, false)};
- public ServletHandlerMappingResolver(){
- this.resourcePatternResolver = ResourcePatternUtils.getResourcePatternResolver(new PathMatchingResourcePatternResolver());
- }
- public ServletHandlerMappingResolver scanPackages(String[] packagesToScan){
- try {
- for (String pkg : packagesToScan) {
- String pattern = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX +
- ClassUtils.convertClassNameToResourcePath(pkg) + RESOURCE_PATTERN;
- Resource[] resources;
- resources = this.resourcePatternResolver.getResources(pattern);
- MetadataReaderFactory readerFactory = new CachingMetadataReaderFactory(this.resourcePatternResolver);
- for (Resource resource : resources) {
- if (resource.isReadable()) {
- MetadataReader reader = readerFactory.getMetadataReader(resource);
- String className = reader.getClassMetadata().getClassName();
- if (matchesFilter(reader, readerFactory)) {
- ServletHandlerMappingFactory.addClassMapping(this.resourcePatternResolver.getClassLoader().loadClass(className));
- }
- }
- }
- }
- } catch (IOException e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- } catch (ClassNotFoundException e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- }
- return this;
- }
- public String[] getPackagesToScan() {
- return packagesToScan;
- }
- public void setPackagesToScan(String[] packagesToScan) {
- this.packagesToScan = packagesToScan;
- this.scanPackages(packagesToScan);
- }
- private boolean matchesFilter(MetadataReader reader, MetadataReaderFactory readerFactory) throws IOException {
- for (TypeFilter filter : ENTITY_TYPE_FILTERS) {
- if (filter.match(reader, readerFactory)) {
- return true;
- }
- }
- return false;
- }
- }
这段代码是Spring中如何扫描Hibernate持久化对象的代码,拿过来借鉴了一下,下面要处理的就是把要处理的URL和相对应的ServletHandler进行匹配:
- package com.meet58.base.servlet.mapping;
- import java.lang.reflect.Method;
- import java.util.HashMap;
- import java.util.Map;
- import org.apache.log4j.Logger;
- import com.meet58.base.servlet.annotation.HandlerMapping;
- import com.meet58.base.servlet.context.ServletHandlerFactory;
- public class ServletHandlerMappingFactory {
- private static Logger logger = Logger.getLogger(ServletHandlerMappingFactory.class);
- private static Map<String, Method> servletHandlerMapping = new HashMap<String, Method>();
- public static void addClassMapping(Class<?> clazz) {
- String url = null;
- HandlerMapping handlerMapping = clazz.getAnnotation(HandlerMapping.class);
- if (handlerMapping != null) {
- url = handlerMapping.value();
- } else {
- String classSimpleName = clazz.getSimpleName().toLowerCase();
- url = "/" + classSimpleName.substring(0,
- classSimpleName.indexOf("servlet"));
- }
- if (url != null) {
- if(url.endsWith("/")){
- url = url.substring(url.length() - 1);
- }
- ServletHandlerFactory.put(clazz);
- logger.info(" Load servlet handler class:" + clazz.getName() + " url:" + url);
- scanHandlerMethod(clazz,url);
- }
- }
- public static void scanHandlerMethod(Class<?> clazz,String classMapping) {
- Method[] methods = clazz.getDeclaredMethods();
- for (Method method : methods) {
- HandlerMapping handlerMapping = method.getAnnotation(HandlerMapping.class);
- if (handlerMapping != null && handlerMapping.value() != null) {
- String mapping = handlerMapping.value();
- if(!mapping.startsWith("/")){
- mapping = "/" + mapping;
- }
- mapping = classMapping + mapping;
- addMethodMapping( mapping,method);
- }
- }
- }
- public static void addMethodMapping(String url,Method method) {
- logger.info(" Load servlet handler mapping, method:" + method.getName() + " for url:" + url);
- Method handlerMethod = servletHandlerMapping.get(url);
- if(handlerMethod != null){
- throw new IllegalArgumentException(" url :" + url + " is already mapped by :" + handlerMethod);
- }else{
- servletHandlerMapping.put(url, method);
- }
- }
- public static Method getMethodMapping(String url) {
- return servletHandlerMapping.get(url);
- }
- }
在这个类中扫描了每个ServletHandler类中的方法,并记录他们的要处理的URL,接下来就是通过容器实例化这些ServletHandler类了:
- package com.meet58.base.servlet.context;
- import java.util.HashMap;
- import java.util.Map;
- import org.apache.log4j.Logger;
- public class ServletHandlerFactory {
- private static Logger logger = Logger.getLogger(ServletHandlerFactory.class);
- private static Map<String,Object> classes = new HashMap<String,Object>();
- public static void put(Class<?> clazz){
- try {
- logger.info("初始化ServletHandler类:"+ clazz.getName());
- Object servlet = clazz.newInstance();
- classes.put(clazz.getName(), servlet);
- } catch (InstantiationException e) {
- logger.error("初始化Servlet类:" + clazz.getName() + "失败:" + e.getMessage());
- } catch (IllegalAccessException e) {
- logger.error("初始化Servlet类:" + clazz.getName() + "失败:" + e.getMessage());
- }
- }
- @SuppressWarnings("unchecked")
- public static <T> T get(String className){
- return (T)classes.get(className);
- }
- }
在ServletHandler类处理完成,并知道他们分别处理哪些URL之后,就可以通过一个调度器进行对对应的URL进行请求的分发了:
- package com.meet58.base.servlet;
- import java.io.IOException;
- import java.lang.reflect.InvocationTargetException;
- import java.lang.reflect.Method;
- import java.util.ArrayList;
- import java.util.List;
- 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 org.apache.log4j.Logger;
- import com.meet58.base.context.WebHttpRequestContext;
- import com.meet58.base.servlet.context.ServletHandlerFactory;
- import com.meet58.base.servlet.mapping.ServletHandlerMappingFactory;
- import com.meet58.util.WebUtils;
- @WebServlet(urlPatterns = { "*.do" })
- public class WebHttpDispatchServlet extends HttpServlet {
- private static final long serialVersionUID = 1L;
- private Logger logger = Logger.getLogger(this.getClass());
- private List<String> excludeUrls = new ArrayList<String>();
- @Override
- public void init() throws ServletException {
- // 屏蔽websocket地址
- excludeUrls.add("/meet.do");
- super.init();
- }
- public void doGet(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- this.doPost(request, response);
- }
- public void doPost(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- try {
- String url = request.getRequestURI().replace(
- request.getContextPath(), "");
- if (excludeUrls.contains(url)) {
- return;
- }
- Method handlerMethod = ServletHandlerMappingFactory.getMethodMapping(url);
- if (handlerMethod == null) {
- response.sendError(404, "No handler found for " + url);
- logger.error("No handler found for " + url);
- return;
- }
- Object servlet = ServletHandlerFactory.get(handlerMethod
- .getDeclaringClass().getName());
- if (servlet == null) {
- response.sendError(404, "No handler class found for " + url);
- logger.error("No handler class found for " + url);
- return;
- }
- Object result = invokeHandlerMethod(servlet, handlerMethod);
- handleInvokeResult(result);
- // this.doService();
- } catch (Throwable e) {
- handlerException(e);
- }
- }
- public void handleInvokeResult(Object result) {
- String location = "";
- if (result instanceof String) {
- if (((String) result).startsWith("redirect:")) {
- location = ((String) result).substring("redirect:".length(),
- ((String) result).length());
- WebUtils.redirect(location);
- } else if (((String) result).startsWith("forward:")) {
- location = ((String) result).substring("forward:".length(),
- ((String) result).length());
- WebUtils.forward(location);
- }
- }
- }
- public Object invokeHandlerMethod(Object object, Method method)
- throws Throwable {
- Object result = null;
- if (method != null) {
- try {
- result = method.invoke(object);
- } catch (InvocationTargetException e) {
- throw e.getTargetException();
- }
- }
- return result;
- }
- public void handlerException(Throwable e) {
- String message = e.getMessage() != null ? e.getMessage() : e.toString();
- e.printStackTrace();
- if (WebHttpRequestContext.isAsyncRequest()) {
- WebUtils.writeFailure(message);
- } else {
- try {
- WebHttpRequestContext.getResponse().sendError(500, message);
- } catch (IOException e1) {
- e1.printStackTrace();
- }
- }
- }
- public String getMappingClass(String url) {
- return null;
- }
- }
这段代码中就是通过URL找到对应的处理方法来进行处理,并且捕获异常。
这种方法Struts也是用到了,不过这个只是简单的兴趣研究并没有在实际项目中运用,可能会存在线程安全的问题。
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