标签：logout 映射 cal extend exception interface row while indexof
最近在用Netty做开发，需要提供一个http web server，供调用方调用。采用Netty本身提供的HttpServerCodec handler进行Http协议的解析，但是需要自己提供路由。
最开始是通过对Http method及uri 采用多层if else 嵌套判断的方法路由到真正的controller类：
String uri = request.uri();
HttpMethod method = request.method();
if (method == HttpMethod.POST) {
if (uri.startsWith("/login")) {
//url参数解析，调用controller的方法
} else if (uri.startsWith("/logout")) {
//同上
}
} else if (method == HttpMethod.GET) {
if (uri.startsWith("/")) {
} else if (uri.startsWith("/status")) {
}
}在只需提供login及logoutAPI时，代码可以完成功能，可是随着API的数量越来越多，需要支持的方法及uri越来越多，else if 越来越多，代码越来越复杂。
在阿里开发手册中也提到过：
因此首先考虑采用状态设计模式及策略设计模式重构。
首先我们知道每个http请求都是由method及uri来唯一标识的，所谓路由就是通过这个唯一标识定位到controller类的中的某个方法。
因此把HttpLabel作为状态
@Data
@AllArgsConstructor
public class HttpLabel {
private String uri;
private HttpMethod method;
}
状态接口：
public interface Route {
/**
* 路由
*
* @param request
* @return
*/
GeneralResponse call(FullHttpRequest request);
}为每个状态添加状态实现：
public void route() {
//单例controller类
final DemoController demoController = DemoController.getInstance();
Map<HttpLabel, Route> map = new HashMap<>();
map.put(new HttpLabel("/login", HttpMethod.POST), demoController::login);
map.put(new HttpLabel("/logout", HttpMethod.POST), demoController::login);
}接到请求，判断状态，调用不同接口：
public class ServerHandler extends SimpleChannelInboundHandler<FullHttpRequest> {
@Override
public void channelRead0(ChannelHandlerContext ctx, FullHttpRequest request) {
String uri = request.uri();
GeneralResponse generalResponse;
if (uri.contains("?")) {
uri = uri.substring(0, uri.indexOf("?"));
}
Route route = map.get(new HttpLabel(uri, request.method()));
if (route != null) {
ResponseUtil.response(ctx, request, route.call(request));
} else {
generalResponse = new GeneralResponse(HttpResponseStatus.BAD_REQUEST, "请检查你的请求方法及url", null);
ResponseUtil.response(ctx, request, generalResponse);
}
}
}使用状态设计模式重构代码，在增加url时只需要网map里面put一个值就行了。
后来看了 JAVA反射+运行时注解实现URL路由 发现反射+注解的方式很优雅，代码也不复杂。
下面介绍Netty使用反射实现URL路由。
路由注解：
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface RequestMapping {
/**
* 路由的uri
*
* @return
*/
String uri();
/**
* 路由的方法
*
* @return
*/
String method();
}扫描classpath下带有@RequestMapping注解的方法，将这个方法放进一个路由Map：Map<HttpLabel, Action<GeneralResponse>> httpRouterAction，key为上面提到过的Http唯一标识 HttpLabel，value为通过反射调用的方法：
@Slf4j
public class HttpRouter extends ClassLoader {
private Map<HttpLabel, Action<GeneralResponse>> httpRouterAction = new HashMap<>();
private String classpath = this.getClass().getResource("").getPath();
private Map<String, Object> controllerBeans = new HashMap<>();
@Override
protected Class<?> findClass(String name) throws ClassNotFoundException {
String path = classpath + name.replaceAll("\\.", "/");
byte[] bytes;
try (InputStream ins = new FileInputStream(path)) {
try (ByteArrayOutputStream out = new ByteArrayOutputStream()) {
byte[] buffer = new byte[1024 * 5];
int b = 0;
while ((b = ins.read(buffer)) != -1) {
out.write(buffer, 0, b);
}
bytes = out.toByteArray();
}
} catch (Exception e) {
throw new ClassNotFoundException();
}
return defineClass(name, bytes, 0, bytes.length);
}
public void addRouter(String controllerClass) {
try {
Class<?> cls = loadClass(controllerClass);
Method[] methods = cls.getDeclaredMethods();
for (Method invokeMethod : methods) {
Annotation[] annotations = invokeMethod.getAnnotations();
for (Annotation annotation : annotations) {
if (annotation.annotationType() == RequestMapping.class) {
RequestMapping requestMapping = (RequestMapping) annotation;
String uri = requestMapping.uri();
String httpMethod = requestMapping.method().toUpperCase();
// 保存Bean单例
if (!controllerBeans.containsKey(cls.getName())) {
controllerBeans.put(cls.getName(), cls.newInstance());
}
Action action = new Action(controllerBeans.get(cls.getName()), invokeMethod);
//如果需要FullHttpRequest，就注入FullHttpRequest对象
Class[] params = invokeMethod.getParameterTypes();
if (params.length == 1 && params[0] == FullHttpRequest.class) {
action.setInjectionFullhttprequest(true);
}
// 保存映射关系
httpRouterAction.put(new HttpLabel(uri, new HttpMethod(httpMethod)), action);
}
}
}
} catch (Exception e) {
log.warn("{}", e);
}
}
public Action getRoute(HttpLabel httpLabel) {
return httpRouterAction.get(httpLabel);
}
}通过反射调用controller 类中的方法：
@Data
@RequiredArgsConstructor
@Slf4j
public class Action<T> {
@NonNull
private Object object;
@NonNull
private Method method;
private boolean injectionFullhttprequest;
public T call(Object... args) {
try {
return (T) method.invoke(object, args);
} catch (IllegalAccessException | InvocationTargetException e) {
log.warn("{}", e);
}
return null;
}ServerHandler.java处理如下：
//根据不同的请求API做不同的处理(路由分发)
Action<GeneralResponse> action = httpRouter.getRoute(new HttpLabel(uri, request.method()));
if (action != null) {
if (action.isInjectionFullhttprequest()) {
ResponseUtil.response(ctx, request, action.call(request));
} else {
ResponseUtil.response(ctx, request, action.call());
}
} else {
//错误处理
generalResponse = new GeneralResponse(HttpResponseStatus.BAD_REQUEST, "请检查你的请求方法及url", null);
ResponseUtil.response(ctx, request, generalResponse);
}测试结果如下：
完整代码在 https://github.com/morethink/Netty-Route
标签：logout 映射 cal extend exception interface row while indexof
原文地址：https://www.cnblogs.com/morethink/p/9710918.html
