springmvc

package com.liugh.servlet;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Method;
import java.net.URL;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Properties;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.liugh.annotation.MyController;
import com.liugh.annotation.MyRequestMapping;

public class MyDispatcherServlet extends HttpServlet {

private Properties properties = new Properties();

private List<String> classNames = new ArrayList<>();

private Map<String, Object> ioc = new HashMap<>();

private Map<String, Method> handlerMapping = new HashMap<>();

private Map<String, Object> controllerMap = new HashMap<>();

@Override
public void init(ServletConfig config) throws ServletException {

// 1.加载配置文件
doLoadConfig(config.getInitParameter("contextConfigLocation"));

// 2.初始化所有相关联的类,扫描用户设定的包下面所有的类
doScanner(properties.getProperty("scanPackage"));

// 3.拿到扫描到的类,通过反射机制,实例化,并且放到ioc容器中(k-v beanName-bean) beanName默认是首字母小写
doInstance();

// 4.初始化HandlerMapping(将url和method对应上)
initHandlerMapping();

}

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doPost(req, resp);
}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
try {
// 处理请求
doDispatch(req, resp);
} catch (Exception e) {
resp.getWriter().write("500!! Server Exception");
}

}

private void doDispatch(HttpServletRequest req, HttpServletResponse resp) throws Exception {
if (handlerMapping.isEmpty()) {
return;
}

String url = req.getRequestURI();
String contextPath = req.getContextPath();

// 拼接url并把多个/替换成一个
url = url.replace(contextPath, "").replaceAll("/+", "/");

if (!this.handlerMapping.containsKey(url)) {
resp.getWriter().write("404 NOT FOUND!");
return;
}

Method method = this.handlerMapping.get(url);

// 获取方法的参数列表
Class<?>[] parameterTypes = method.getParameterTypes();

// 获取请求的参数
Map<String, String[]> parameterMap = req.getParameterMap();

// 保存参数值
Object[] paramValues = new Object[parameterTypes.length];

// 方法的参数列表
for (int i = 0; i < parameterTypes.length; i++) {
// 根据参数名称，做某些处理
String requestParam = parameterTypes[i].getSimpleName();

if (requestParam.equals("HttpServletRequest")) {
// 参数类型已明确，这边强转类型
paramValues[i] = req;
continue;
}
if (requestParam.equals("HttpServletResponse")) {
paramValues[i] = resp;
continue;
}
if (requestParam.equals("String")) {
for (Entry<String, String[]> param : parameterMap.entrySet()) {
String value = Arrays.toString(param.getValue()).replaceAll("\\[|\\]", "").replaceAll(",\\s", ",");
paramValues[i] = value;
}
}
}
// 利用反射机制来调用
try {
method.invoke(this.controllerMap.get(url), paramValues);// obj是method所对应的实例
// 在ioc容器中
} catch (Exception e) {
e.printStackTrace();
}
}

private void doLoadConfig(String location) {
// 把web.xml中的contextConfigLocation对应value值的文件加载到留里面
InputStream resourceAsStream = this.getClass().getClassLoader().getResourceAsStream(location);
try {
// 用Properties文件加载文件里的内容
properties.load(resourceAsStream);
} catch (IOException e) {
e.printStackTrace();
} finally {
// 关流
if (null != resourceAsStream) {
try {
resourceAsStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}

}

private void doScanner(String packageName) {
// 把所有的.替换成/
URL url = this.getClass().getClassLoader().getResource("/" + packageName.replaceAll("\\.", "/"));
File dir = new File(url.getFile());
for (File file : dir.listFiles()) {
if (file.isDirectory()) {
// 递归读取包
doScanner(packageName + "." + file.getName());
} else {
String className = packageName + "." + file.getName().replace(".class", "");
classNames.add(className);
}
}
}

private void doInstance() {
if (classNames.isEmpty()) {
return;
}
for (String className : classNames) {
try {
// 把类搞出来,反射来实例化(只有加@MyController需要实例化)
Class<?> clazz = Class.forName(className);
if (clazz.isAnnotationPresent(MyController.class)) {
ioc.put(toLowerFirstWord(clazz.getSimpleName()), clazz.newInstance());
} else {
continue;
}

} catch (Exception e) {
e.printStackTrace();
continue;
}
}
}

private void initHandlerMapping() {
if (ioc.isEmpty()) {
return;
}
try {
for (Entry<String, Object> entry : ioc.entrySet()) {
Class<? extends Object> clazz = entry.getValue().getClass();
if (!clazz.isAnnotationPresent(MyController.class)) {
continue;
}

// 拼url时,是controller头的url拼上方法上的url
String baseUrl = "";
if (clazz.isAnnotationPresent(MyRequestMapping.class)) {
MyRequestMapping annotation = clazz.getAnnotation(MyRequestMapping.class);
baseUrl = annotation.value();
}
Method[] methods = clazz.getMethods();
for (Method method : methods) {
if (!method.isAnnotationPresent(MyRequestMapping.class)) {
continue;
}
MyRequestMapping annotation = method.getAnnotation(MyRequestMapping.class);
String url = annotation.value();

url = (baseUrl + "/" + url).replaceAll("/+", "/");
// 这里应该放置实例和method
handlerMapping.put(url, method);
controllerMap.put(url, clazz.newInstance());
System.out.println(url + "," + method);
}

}

} catch (Exception e) {
e.printStackTrace();
}

}

/**
* 把字符串的首字母小写
*
* @param name
* @return
*/
private String toLowerFirstWord(String name) {
char[] charArray = name.toCharArray();
charArray[0] += 32;
return String.valueOf(charArray);
}

}