1、项目整体结构如下图
image.png
2、myDispatcherServlet
package com.test.springmvc.servlet;
import com.test.springmvc.annotation.*;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Parameter;
import java.net.URL;
import java.util.*;
public class myDispatcherServlet extends HttpServlet {
/**
* 配置文件
*/
private static final Properties properties = new Properties();
/*
* 扫描的包中的类列表
*/
private static final List<String> classList = new ArrayList<>();
/**
* 实例化map，记录类名个类的实例的映射关系
*/
private static final Map<String, Object> instanceMap = new HashMap<>();
/**
* 方法执行器map-, url对用的method
*/
private static final Map<String, Method> handlerMappingMap = new HashMap<>();
/**
* RequestMapping的url，对应的在哪一个controller中
*/
private static final Map<String, Object> requestMapUrl2Controller = new HashMap<>();
/**
* 每一个类的baseUrl
* 每一个controller都有一个Url：key=controller类名字，value=baseUrl
*/
private static final Map<String, String> baseURLMap = new HashMap<String,
String>();
@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 {
String uri = req.getRequestURI();
String contextPath = req.getContextPath();
System.out.println("req.getRequestURI()=" + uri);
System.out.println("req.getContextPath()=" + contextPath);
/**
* 去掉项目根目录springmvc/
*/
String url = uri.replace(contextPath, "");
System.out.println("url=" + url);
Method method = handlerMappingMap.get(url);
if (method == null) {
return;
}
//获取方法的参数列表
/**
* 获取所有对象的类别
*/
Class<?>[] parameterTypes = method.getParameterTypes();
/**
* 获取入参
*/
Map<String, String[]> parameterMap = req.getParameterMap();
/**
* 存放参数的数组
*/
Object[] paramValues = new Object[parameterTypes.length];
Parameter[] parameters = method.getParameters();
for (final Parameter parameter : parameters) {
System.out.println("parameter=" + parameter.getName() + ' ');
}
for (int i = 0; i < parameterTypes.length; i++) {
String paramName = parameterTypes[i].getSimpleName();
/**
* 如果是HttpServletRequest
*/
if (paramName.equals("HttpServletRequest")) {
paramValues[i] = req;
continue;
}
/**
* 如果是HttpServletResponse
*/
if (paramName.equals("HttpServletResponse")) {
paramValues[i] = resp;
continue;
}
/**
* 参数类型是String
*/
if (paramName.equals("String")) {
String[] values = null;
// 参数带有RequestParam注解
if (parameters[i].isAnnotationPresent(RequestParam.class)
&& !parameters[i].getAnnotation(RequestParam.class).value().equals("")) {
RequestParam requestParam = parameters[i].getAnnotation(RequestParam.class);
values = parameterMap.get(requestParam.value());
} else {
System.out.println(parameters[i].getName());
values = parameterMap.get(parameters[i].getName());
}
System.out.println("parameter values=" + Arrays.toString(values));
if (values != null) {
//去除多余的【】，例如传入的参数为【zfd】，我们要的字符串是zfd，需要去除去除【】
paramValues[i] = Arrays.toString(values).replaceAll("\\[", "").replaceAll("\\]", "")
.replaceAll(",s", ",");
}
}
if (paramName.equals("int") || paramName.equals("Integer")) {
String[] values = parameterMap.get(parameters[i].getName());
System.out.println(Arrays.toString(values));//[20]
paramValues[i] =
//如果是Integer，Arrays.toString(values)的结果是[20]，需要去掉[]
Integer.parseInt(Arrays.toString(values).replace("[",
"").replace("]", ""));
}
}
/**
* 通过url获取controller实例
*/
Object o = requestMapUrl2Controller.get(url);
// System.out.println(o);
try {
method.invoke(o, paramValues);
} catch (IllegalAccessException e) {
e.printStackTrace();
resp.getWriter().write("<h1>500..." + e.getLocalizedMessage() +
"</h1>");
} catch (InvocationTargetException e) {
e.printStackTrace();
resp.getWriter().write("<h1>500..." + e.getLocalizedMessage() + "</h1>");
} catch (IllegalArgumentException e) {
e.printStackTrace();
resp.getWriter().write("<h1>500..." + e.getLocalizedMessage() + "</h1>");
}
}
@Override
public void destroy() {
System.out.println("Server ShutDown");
}
@Override
public void init() throws ServletException {
System.out.println("server init begin ...");
/**
* 加载配置文件
*/
doLoadProperties();
/**
* 扫描所有类
*/
String baseUrl = doScannerClazz();
/**
* 获得实例
*/
doInstance(baseUrl);
/**
* 执行mapping
*/
doHandlerMapping();
System.out.println("server end init ...");
}
private void doHandlerMapping() {
if (instanceMap.size() > 0) {
for (Map.Entry<String, Object> entry : instanceMap.entrySet()) {
String key = entry.getKey();
Object object = instanceMap.get(key);
/**
* 获取该controller类对应的baseUrl
*/
// System.out.println(""+object.getClass().getSimpleName());
String baseUrl = baseURLMap.get(object.getClass().getSimpleName());
Method[] methods = object.getClass().getMethods();
for (Method method : methods) {
if (method.isAnnotationPresent(RequestMapping.class)) {
RequestMapping annotation = method.getAnnotation(RequestMapping.class);
String defaultUrl = annotation.value();
String url = baseUrl + defaultUrl;
/**
* 请求路径和执行的方法的关系映射
*/
// System.out.println(url);
// System.out.println(method);
if (handlerMappingMap.containsKey(url)) {
System.err.println(url);
System.err.println(method);
System.out.println("url already exist，url=" + url +
", method=" + method);
System.exit(0);
}
handlerMappingMap.put(url, method);
/**
* 请求url映射哪一个controller实例类
*/
requestMapUrl2Controller.put(url, entry.getValue());
}
}
}
}
System.out.println(handlerMappingMap);
System.out.println(requestMapUrl2Controller);
System.out.println(instanceMap);
}
private void doInstance(String baseUrl) {
List<String> services = new ArrayList<>();
List<String> daos = new ArrayList<>();
List<String> controllers = new ArrayList<>();
try {
if (!classList.isEmpty()) {
for (String clazzName : classList) {
if (clazzName.endsWith("Service")) {
services.add(clazzName);
}
if (clazzName.endsWith("Dao")) {
daos.add(clazzName);
}
if (clazzName.endsWith("Controller")) {
controllers.add(clazzName);
}
}
//1、先处理service下的类
String serviceBaseUrl= (baseUrl + "service/").replace("/", ".");
System.out.println("serviceBaseUrl="+serviceBaseUrl);
for (String clazzName : services) {
Class<?> aClass =
Class.forName(serviceBaseUrl+clazzName);
if (aClass.isAnnotationPresent(Service.class)) {
Object instance = aClass.newInstance();
Service annotation = aClass.getAnnotation(Service.class);
String value = annotation.value();
if (value.equals("")) {
value = aClass.getSimpleName();
System.out.println("obj.getClass().getSimpleName()=" + value);
}
instanceMap.put(value, instance);
}
}
//2、在处理dao下的类
String daoBaseUrl= (baseUrl + "dao/").replace("/", ".");
System.out.println("daoBaseUrl="+daoBaseUrl);
for (String clazzName : daos) {
Class<?> aClass = Class.forName(daoBaseUrl + clazzName);
if (aClass.isAnnotationPresent(Component.class)) {
Object instance = aClass.newInstance();
Component annotation = aClass.getAnnotation(Component.class);
String value = annotation.value();
if (value.equals("")) {
value = aClass.getSimpleName();
System.out.println("obj.getClass().getSimpleName()=" + value);
}
/**
* 处理Dao中的带有Autowired的service
*/
Field[] declaredFields = aClass.getDeclaredFields();
for(Field field:declaredFields){
System.out.println(field.getName());
if(field.isAnnotationPresent(Autowired.class)){
String name = field.getName();
Object fieldInstance = instanceMap.get(name);
// System.out.println(instanceMap);
if(fieldInstance==null){
System.out.println("can not find bean="+name);
System.exit(0);
}
//设置带有Autowired注解的实例是那一个对象
field.setAccessible(true);
field.set(instance,fieldInstance);
System.out.println("Autowired success, "+name);
System.out.println(field.get(instance));
}
}
instanceMap.put(value, instance);
}
}
//3、最后处理controller下的类
String controllerBaseUrl= (baseUrl + "controller/").replace("/", ".");
System.out.println("controllerBaseUrl="+controllerBaseUrl);
for (String clazzName : controllers) {
Class<?> aClass =
Class.forName(controllerBaseUrl+clazzName);
if (aClass.isAnnotationPresent(Controller.class)) {
Object instance = aClass.newInstance();
Controller annotation = aClass.getAnnotation(Controller.class);
String value = annotation.value();
if (value.equals("")) {
value = aClass.getSimpleName();
}
/**
* 处理controller中的带有Autowired的属性
*/
Field[] declaredFields = aClass.getDeclaredFields();
for(Field field:declaredFields){
if(field.isAnnotationPresent(Autowired.class)){
String name = field.getName();
Object fieldInstance = instanceMap.get(name);
// System.out.println(instanceMap);
if(fieldInstance==null){
System.out.println("can not find bean="+name);
System.exit(0);
}
//设置带有Autowired注解的实例是那一个对象
field.setAccessible(true);
field.set(instance,fieldInstance);
System.out.println("Autowired success, "+name);
}
}
instanceMap.put(value, instance);
}
if (aClass.isAnnotationPresent(RequestMapping.class)) {
Object newInstance = aClass.newInstance();
RequestMapping annotation = aClass.getAnnotation(RequestMapping.class);
String url = annotation.value();
if (url.equals("")) {
url = "/" + newInstance.getClass().getSimpleName();
System.out.println("clazzName=" + clazzName + " " +
"baseUrl is=" + baseUrl);
}
System.out.println("clazzName=" + clazzName);
System.out.println("baseUrl=" + url);
baseURLMap.put(clazzName, url);
}
}
}
} catch (ClassNotFoundException | IllegalAccessException | InstantiationException e) {
e.printStackTrace();
}
}
/**
* 加载basePackage下的类
*/
private String doScannerClazz() {
if (properties != null) {
String basePackage = properties.getProperty("basePackage").trim();
if (!basePackage.equals("") && basePackage.length() > 0) {
basePackage = basePackage.replaceAll("\\.", "/");
System.out.println("basePackage:" + basePackage);
String controllerBaseUrl = basePackage;
String serviceBaseUrl = basePackage;
String daoBaseUrl = basePackage;
//加载顺序service-> dao-> controller,不能变
/**
* 1、加载service下的类
*/
URL url =
this.getClass().getClassLoader().getResource(serviceBaseUrl.replace("*", "service"));
if (url != null) {
String path = url.getFile();
File file = new File(path);
String[] list = file.list();
for (String f : list) {
System.out.println("load service class=" + f);
if (f.endsWith(".class")) {
classList.add(f.split("\\.")[0]);
}
}
}
/**
* 2、加载dao下的类
*/
url =
this.getClass().getClassLoader().getResource(daoBaseUrl.replace("*", "dao"));
if (url != null) {
String path = url.getFile();
File file = new File(path);
String[] list = file.list();
for (String f : list) {
System.out.println("load dao class=" + f);
if (f.endsWith(".class")) {
classList.add(f.split("\\.")[0]);
}
}
}
/**
* 3、加载controller下的类
*/
url =
this.getClass().getClassLoader().getResource(controllerBaseUrl.replace("*", "controller"));
if (url != null) {
String path = url.getFile();
File file = new File(path);
String[] list = file.list();
for (String f : list) {
System.out.println("load controller class=" + f);
if (f.endsWith(".class")) {
classList.add(f.split("\\.")[0]);
}
}
}
return basePackage.replace("*","");
}
}
return null;
}
/**
* application.properties 优先
*/
private void doLoadProperties() {
InputStream stream1 =
this.getClass().getClassLoader().getResourceAsStream("application" +
".properties");
try {
properties.load(stream1);
} catch (IOException e) {
e.printStackTrace();
}
}
}
3、web.xml配置
<servlet>
<servlet-name>dispatcher</servlet-name>
<servlet-class>com.test.springmvc.servlet.myDispatcherServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>dispatcher</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
</servlet>
4、controller举一个例子
TestController
package com.test.controller;
import com.test.dao.UserDao;
import com.test.pojo.req.Person;
import com.test.springmvc.annotation.Autowired;
import com.test.springmvc.annotation.Controller;
import com.test.springmvc.annotation.RequestMapping;
import com.test.springmvc.annotation.RequestParam;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@Controller
@RequestMapping("/test")
public class TestController {
@Autowired
private UserDao userDao;
@RequestMapping("/hello")
public String hello(HttpServletResponse response){
try {
response.getWriter().write("test hello");
} catch (IOException e) {
e.printStackTrace();
}
return "";
}
@RequestMapping("/hello2")
public String hello2(HttpServletResponse response,
@RequestParam String name,
@RequestParam String age){
try {
response.getWriter().write("hello "+name+",your age is "+age);
} catch (IOException e) {
e.printStackTrace();
}
return "";
}
@RequestMapping("/hello3")
public String hello3(HttpServletResponse response,
@RequestParam(value = "name") String name,
@RequestParam Integer age){
try {
response.getWriter().write("hello "+name+",your age is "+age);
} catch (IOException e) {
e.printStackTrace();
}
return "";
}
@RequestMapping("/getUserInfo")
public String getFromSql(HttpServletResponse response,
@RequestParam(value = "name") String name){
try {
Person person = userDao.getUserInfoByName(name);
response.getWriter().write(person.toString());
} catch (IOException e) {
e.printStackTrace();
}
return "";
}
}
5、测试
image.png
6、源码githubs：https://github.com/zhoufudun/springmvc
7、总结
1、难点在于熟练掌握反射相关技术，多练练也没什么难的
2、尝试过用tomcat跑起来，但是失败了，直接用jetty方便得多
3、其实还可以仿造springboot的注解，例如Bean、Configuration、ConditionOnProperties、Component实现自己的逻辑等。
8、补充实现Autowired、Component、Service注解的实现
