前言
如果你稍微留意下commit就会这个项目早在好２个月前就创建了，我也一直想写下，但是确实太懒了就一直拖着着。这几天由于没有太多开发任务就有想写了。
依赖环境
-
jdk:１.8
-
tomcat8.5
-
servlet3.1.0
-
maven3.6.0
正文
1. 这个项目又两个分支：webxml和nowebxml，我开始是基于servlet2.5写的，后面我又想用servlet3.x了于是就两个分支了（后面主要代码都在nowebxml上）。
2. Servlet容器启动会扫描，当前应用里面每一个jar包的ServletContainerInitializer的实现，然后就注入一个DispatcherServlet 就可以了,跟在web.xml配置一样，只是这里都在java代码里面了（看过spring代码的同学可能一眼就看出了它也是有个SpringServletContainerInitializer类作为人口的）
public class SpringxServletContainerInitializer implements ServletContainerInitializer {
@Override
public void onStartup(Set<Class<?>> c, ServletContext ctx) {
ServletRegistration.Dynamic dispatcherServlet = ctx.addServlet("dispatcherServlet", DispatcherServlet.class);
dispatcherServlet.setInitParameter("scanPackage", "com.sunny.springx.example");
dispatcherServlet.addMapping("/*");
dispatcherServlet.setLoadOnStartup(1);
}
}
3.上面代码可以看出有个scanPackage参数，这个是告诉springx从那里开始工作。DispatcherServlet继承HttpServlet所以开始会调用init方法，然后就是大概四步就可以完成一个简单的springx
@Override
public void init(ServletConfig config) {
Instant start = Instant.now();
// 1.扫描相关类
doScanner(config.getInitParameter("scanPackage"));
// 2.初始化类
doInstance();
// 3. 注入
doAutoWried();
// 4. 初始化url
initHandlerMapping();
Instant end = Instant.now();
System.out.println("springx init in " + Duration.between(start, end).toMillis() + " ms");
}
4. 主要逻辑都在DispatcherServlet这里面
public class DispatcherServlet extends HttpServlet {
//存放class name
private List<String> classNames = new ArrayList<>();
// ioc 容器
private Map<String, Object> ioc = new HashMap<>();
//handMapping
private List<Handler> handlerMapping = new ArrayList<>();
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
try {
doDispatch(req, resp);
} catch (Exception e) {
resp.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
resp.getWriter().write("500 " + e.getMessage());
}
}
private void doDispatch(HttpServletRequest req, HttpServletResponse resp) throws IOException, InvocationTargetException, IllegalAccessException {
String url = req.getRequestURI();
String contextPath = req.getContextPath();
url = url.replace(contextPath, "").replaceAll("/+", "/");
Handler handler = getHandler(url);
//url 不存在４０４
if (Objects.isNull(handler)) {
resp.setStatus(HttpServletResponse.SC_NOT_FOUND);
resp.getWriter().write("not found url : " + url);
return;
}
// 获取方法
Object invoke = handler.method.invoke(handler.controller, null);
resp.setStatus(HttpServletResponse.SC_OK);
resp.getWriter().write(invoke.toString());
}
@Override
public void init(ServletConfig config) {
Instant start = Instant.now();
// 1.扫描相关类
doScanner(config.getInitParameter("scanPackage"));
// 2.初始化类
doInstance();
// 3. 注入
doAutoWried();
// 4. 初始化url
initHandlerMapping();
Instant end = Instant.now();
System.out.println("springx init in " + Duration.between(start, end).toMillis() + " ms");
}
/**
* 获取 handler
*
* @param url 请求url
* @return
*/
private Handler getHandler(String url) {
if (handlerMapping.isEmpty()) return null;
for (Handler handler : handlerMapping) {
Matcher matcher = handler.pattern.matcher(url);
if (!matcher.matches()) continue;
return handler;
}
return null;
}
private void initHandlerMapping() {
if (ioc.isEmpty()) return;
for (Map.Entry<String, Object> entry : ioc.entrySet()) {
// 获取类
Class<?> clazz = entry.getValue().getClass();
//没有controller注解的跳过
if (!clazz.isAnnotationPresent(Controller.class)) continue;
//根ｕｒｌ
String rootUrl = "";
if (clazz.isAnnotationPresent(RequestMapping.class)) {
RequestMapping requestMapping = clazz.getAnnotation(RequestMapping.class);
rootUrl = requestMapping.value();
}
//扫描类全部方法
for (Method method : clazz.getMethods()) {
//只处理RequestMapping注解
if (!method.isAnnotationPresent(RequestMapping.class)) continue;
RequestMapping requestMapping = method.getAnnotation(RequestMapping.class);
// 拼接rootUrl 全局替换避免两个斜杠 正则
String reg = ("/" + rootUrl + requestMapping.value()).replaceAll("/+", "/");
handlerMapping.add(new Handler(method, entry.getValue(), Pattern.compile(reg)));
System.out.println("mapping:" + reg + "," + method);
}
}
}
private void doAutoWried() {
if (ioc.isEmpty()) return;
for (Map.Entry<String, Object> entry : ioc.entrySet()) {
// 获取类中全部的字段
Field[] fields = entry.getValue().getClass().getDeclaredFields();
for (Field field : fields) {
// 不包含autowried注解的跳过
if (!field.isAnnotationPresent(Autowried.class)) continue;
Autowried autowried = field.getAnnotation(Autowried.class);
String beanId = autowried.value().trim();
if (StringUtils.isBlank(beanId)) {
beanId = field.getName();
}
//设置授权
field.setAccessible(true);
try {
// 字段赋值
field.set(entry.getValue(), ioc.get(beanId));
} catch (IllegalAccessException ex) {
ex.printStackTrace();
}
}
}
}
private void doInstance() {
if (classNames.isEmpty()) return;
try {
for (String className : classNames) {
//根据名称实例化加了controller和service注解的类
Class<?> clazz = Class.forName(className);
//beanId 默认类小写
String beanId;
if (clazz.isAnnotationPresent(Controller.class)) {// 处理Controller注解
Controller controller = clazz.getAnnotation(Controller.class);
beanId = controller.value();
if (StringUtils.isBlank(beanId)) {
beanId = StringUtils.lowerFirstCase(clazz.getSimpleName());
}
ioc.put(beanId, clazz.newInstance());
} else if (clazz.isAnnotationPresent(Service.class)) { // 处理Service 注解
// 获取注解
Service service = clazz.getAnnotation(Service.class);
beanId = service.value();
if (StringUtils.isBlank(beanId)) {
beanId = StringUtils.lowerFirstCase(clazz.getSimpleName());
}
Object instance = clazz.newInstance();
ioc.put(beanId, instance);
// 获取类的实现
for (Class<?> anInterface : clazz.getInterfaces()) {
ioc.put(StringUtils.lowerFirstCase(anInterface.getSimpleName()), instance);
}
}
}
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException e) {
e.printStackTrace();
}
}
/**
* 加载路径下的全部class name
*
* @param scanPackage 包开始扫描路径
*/
private void doScanner(String scanPackage) {
// com.sunny.springx.example 路径替换文件路径
URL url = getClassLoader().getResource("/" + scanPackage.replaceAll("\\.", "/"));
assert url != null;
File classDir = new File(url.getFile());
for (File file : Objects.requireNonNull(classDir.listFiles())) {
//如果是文件夹继续扫描
if (file.isDirectory()) {
doScanner(scanPackage + "." + file.getName());
} else {
String className = scanPackage + "." + file.getName().replaceAll(".class", "");
classNames.add(className);
}
}
}
private ClassLoader getClassLoader() {
return this.getClass().getClassLoader();
}
private class Handler {
Method method;
//方法对象实力
Object controller;
//url正则
Pattern pattern;
Handler(Method method, Object controller, Pattern pattern) {
this.method = method;
this.controller = controller;
this.pattern = pattern;
}
}
}
结尾
这个项目写的比较粗糙，后面有时间我打算把spring的能力都在这个项目里面体现下。比如参数绑定我就没有实现，只是定义了注解还没有实现。当然你也可以fork去写这玩玩，感谢围观
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