手撕Spring
源码地址
实现思路
引入依赖
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
<scope>provided</scope>
</dependency>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
<encoding>UTF-8</encoding>
<compilerArgs>
<arg>-parameters</arg>
</compilerArgs>
</configuration>
</plugin>
<plugin>
<groupId>org.mortbay.jetty</groupId>
<artifactId>maven-jetty-plugin</artifactId>
<version>6.1.26</version>
</plugin>
目录及功能介绍
|-- src
|--main
|-- cn
|-- jihongyun
|-- framework
|-- core
|-- annotation
|-- Autowired.java
|-- Controller.java
|-- RequestMapping.java
|-- ReqeustParam.java
|-- Service.java
|-- RedCloudDispatcherServlet.java
|-- demo
|-- controller
|-- TestController.java
|-- service
|-- imp
|-- TestServiceImp.java
|-- TestServcie.java
|-- resources
|-- application.properties
|-- webapp
|-- WEB-INF
|-- web.xml
cn.jihongyun.framework.core.annotation中模拟了spring的注解，标记类、方法或参数。
RedCloudDispatcherServlet.java 实现了HttpServlet中的init(ServletConfig config)、doGet(req,resp)、doPost(req,resp)方法。
demo文件夹中是一个单元测试
web.xml配置
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:javaee="http://java.sun.com/xml/ns/javaee"
xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
version="2.4">
<display-name>RedCloud Web Application</display-name>
<servlet>
<!--服务名-->
<servlet-name>redCloudMvc</servlet-name>
<!--服务的初始化类-->
<servlet-class>cn.jihongyun.framework.core.RedCloudDispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>application.properties</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>redCloudMvc</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
</web-app>
自定义配置文件application.properties
scanPackage=cn.jihongyun.demo
初始化阶段 init(ServletConfig config)
// 加载配置配置
doLoadConfig(config.getInitParameter("contextConfigLocation"));
//扫描相关类信息
doScanner(properties.getProperty("scanPackage"));
//实例化保存至容器中
doInstance();
//完成依赖注入
doAutowired();
//初始化HandlerMapping
initHandlerMapping();
log.info("RedCloud Spring framework init finished.");
加载application.properties文件中的信息
private void doLoadConfig(String contextconfigLocation) {
InputStream resourceAsStream = this.getClass().getClassLoader().getResourceAsStream(contextconfigLocation);
try {
properties.load(resourceAsStream);
} catch (IOException e) {
e.printStackTrace();
}finally {
if (null != resourceAsStream) {
try {
resourceAsStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
获取需要扫描的包路径
private void doScanner(String scanPackage) {
URL url = this.getClass().getClassLoader().getResource("/" + scanPackage.replaceAll("\\.", "/"));
if (url == null) {
log.info("scanPackage no exits.");
return;
}
File parent = new File(url.getFile());
for (File file : parent.listFiles()) {
if (file.isDirectory()) {
doScanner(scanPackage+"."+file.getName());
} else {
if (!file.getName().endsWith(".class")) {
continue;
}
String classname = scanPackage + "." + file.getName().replace(".class", "");
classNames.add(classname);
}
}
}
实例化容器保存至IOC容器中
private void doInstance() {
if (classNames.isEmpty()) {
return;
}
try {
for (String className : classNames) {
Class<?> aClass = Class.forName(className);
if (aClass.isAnnotationPresent(Controller.class)) {
Object ins = aClass.newInstance();
String beanName = toLowerFirstCase(aClass.getSimpleName());
ioc.put(beanName, ins);
} else if (aClass.isAnnotationPresent(Service.class)){
Object instance = aClass.newInstance();
Service annotation = aClass.getAnnotation(Service.class);
String beanName = annotation.value();
if (beanName.equals("")) {
beanName = toLowerFirstCase(aClass.getInterfaces()[0].getSimpleName());
}
ioc.put(beanName, instance);
}
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
完成依赖注入
private void doAutowired() {
if (ioc.isEmpty()) {
return;
}
for (Map.Entry<String, Object> entry : ioc.entrySet()) {
Field[] fields = entry.getValue().getClass().getDeclaredFields();
for (Field field : fields) {
if (!field.isAnnotationPresent(Autowired.class)) {
continue;
}
String beanName = toLowerFirstCase(field.getType().getSimpleName());
// 暴力访问，强制赋值
field.setAccessible(true);
try {
// 通过反射，动态给字段赋值
field.set(entry.getValue(),ioc.get(beanName));
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
}
}
初始化requestMapping请求规则
private void doDispatcher(HttpServletRequest req, HttpServletResponse resp) throws IOException, InvocationTargetException, IllegalAccessException {
//根据请求获取对应处理的handler
Handler handler = getHandler(req);
if (handler == null) {
resp.getWriter().write("404 Not Found!!!");
return;
}
// 获取方法的参数类型并赋值
Class<?>[] paramType = handler.getParamType();
Object[] paramValues = new Object[paramType.length];
Map<String, String[]> reqParameterMap = req.getParameterMap();
for (Map.Entry<String, String[]> param : reqParameterMap.entrySet()) {
String value = Arrays.toString(param.getValue()).replaceAll("\\[|\\]", "").replaceAll("\\s", ",");
if (!handler.paramIndexMapping.containsKey(param.getKey())) {
continue;
}
Integer index = handler.paramIndexMapping.get(param.getKey());
paramValues[index] = convert(paramType[index], value);
}
if (handler.paramIndexMapping.containsKey(HttpServletRequest.class.getName())) {
Integer reqIndex = handler.paramIndexMapping.get(HttpServletRequest.class.getName());
paramValues[reqIndex] = req;
}
if (handler.paramIndexMapping.containsKey(HttpServletResponse.class.getName())) {
Integer respIndex = handler.paramIndexMapping.get(HttpServletResponse.class.getName());
paramValues[respIndex] = resp;
}
// 反射调用返回结果
Object returnValue = handler.method.invoke(handler.controller, paramValues);
if (returnValue == null || returnValue instanceof Void) {
return;
}
resp.getWriter().write(returnValue.toString());
}
请求匹配处理阶段
此阶段根据请求路径获取对应的处理方法，反射调用，返回结果。
private void doDispatcher(HttpServletRequest req, HttpServletResponse resp) throws IOException, InvocationTargetException, IllegalAccessException {
//根据请求获取对应处理的handler
Handler handler = getHandler(req);
if (handler == null) {
resp.getWriter().write("404 Not Found!!!");
return;
}
// 获取方法的参数类型并赋值
Class<?>[] paramType = handler.getParamType();
Object[] paramValues = new Object[paramType.length];
Map<String, String[]> reqParameterMap = req.getParameterMap();
for (Map.Entry<String, String[]> param : reqParameterMap.entrySet()) {
String value = Arrays.toString(param.getValue()).replaceAll("\\[|\\]", "").replaceAll("\\s", ",");
if (!handler.paramIndexMapping.containsKey(param.getKey())) {
continue;
}
Integer index = handler.paramIndexMapping.get(param.getKey());
paramValues[index] = convert(paramType[index], value);
}
if (handler.paramIndexMapping.containsKey(HttpServletRequest.class.getName())) {
Integer reqIndex = handler.paramIndexMapping.get(HttpServletRequest.class.getName());
paramValues[reqIndex] = req;
}
if (handler.paramIndexMapping.containsKey(HttpServletResponse.class.getName())) {
Integer respIndex = handler.paramIndexMapping.get(HttpServletResponse.class.getName());
paramValues[respIndex] = resp;
}
// 反射调用返回结果
Object returnValue = handler.method.invoke(handler.controller, paramValues);
if (returnValue == null || returnValue instanceof Void) {
return;
}
resp.getWriter().write(returnValue.toString());
}
总结
通过demo简单模仿了SpringMVC，了解SpringMVC整个调用链路。
03 May 2025