手写spring(简易版)
本文版权归 远方的风lyh和博客园共有，欢迎转载，但须保留此段声明，并给出原文链接，谢谢合作，如有错误之处忘不吝批评指正!
理解Spring本质:
相信之前在使用spring的时候大家都配置web.xml文件、会配置spring，(如下)配置其实就是一个Servlet，DispatcherServlet源码中，它(父类)重写了 HttpServlet接口,所有的请求将交给 DispatcherServlet来处理了 <servlet>
<servlet-name>spring-mvc</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <init-param> <param-name>contextConfigLocation</param-name> <param-value>WEB-INF/spring/spring-mvc.xml</param-value> </init-param> <load-on-startup>1</load-on-startup> <async-supported>true</async-supported> </servlet> <servlet-mapping> <servlet-name>spring-mvc</servlet-name> <url-pattern>/</url-pattern>
</servlet-mapping>
配置
web.xm: 配置一个servlet 并接收所有请求
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd" > <web-app> <display-name>Archetype Created Web Application</display-name> <servlet> <servlet-name>MySpringMVC</servlet-name> <servlet-class>cn.lyh.mySpring.MyDispatcherServlet</servlet-class> <init-param> <param-name>contextConfigLocation</param-name> <param-value>context.properties</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>MySpringMVC</servlet-name> <url-pattern>/*</url-pattern> </servlet-mapping> </web-app>
context.properties：
#包扫描 scan.package=cn.lyh.mySpringTest
注解类
@Target(ElementType.FIELD) @Retention(RetentionPolicy.RUNTIME) @Documented public @interface MyAutowired { String value() default ""; } @Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented public @interface MyController { String value() default ""; } @Target({ElementType.TYPE, ElementType.METHOD}) @Retention(RetentionPolicy.RUNTIME) @Documented public @interface MyRequestMapping { String value() default ""; } @Target(ElementType.PARAMETER) @Retention(RetentionPolicy.RUNTIME) @Documented public @interface MyRequestParam { /** * 表示参数的别名，必填 * @return */ String value(); } @Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented public @interface MyResponseAdvice { } @Target(ElementType.METHOD) @Retention(RetentionPolicy.RUNTIME) @Documented public @interface MyResponseBody { } @Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented public @interface MyService { String value() default ""; }
MyDispacherServlet(核心实现)：
MyDispacherServlet实现了HttpServlet 并复写doGet、doPost、init 方法
·
package cn.lyh.mySpring; import cn.lyh.mySpring.Handler.ResponseBodyHandler; import cn.lyh.mySpring.annotation.*; import com.alibaba.fastjson.JSONObject; import com.alibaba.fastjson.serializer.SerializerFeature; import org.apache.log4j.Logger; import javax.servlet.ServletConfig; import javax.servlet.ServletException; import javax.servlet.ServletRequest; import javax.servlet.ServletResponse; 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.io.PrintWriter; 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.*; /*** *dispatcherServlet * @author lyh */ public class MyDispatcherServlet extends HttpServlet { /***配置***/ private Properties contextConfig = new Properties(); /***扫描的类名列表****/ private List<String> classNames = new ArrayList<>(); /***ioc容器 存放实例****/ private Map<String, Object> ioc = new HashMap<>(); /***url映射****/ private Map<String, Method> handlerMapping = new HashMap<>(); private static Logger logger = Logger.getLogger(MyDispatcherServlet.class); /***返回处理器****/ private ResponseBodyHandler responseBodyHandler; @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doPost(req, resp); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doDispatcherServlet(req, resp); } /**** * 加载启动 * @param config * @throws ServletException */ @Override public void init(ServletConfig config) throws ServletException { String contextConfigLocation = config.getInitParameter("contextConfigLocation"); try { initMyDispatcherServlet(contextConfigLocation); } catch (Exception e) { e.printStackTrace(); throw new ServletException(e.getMessage()); } } /*** * url请求映射到具体方法 * @param request * @param response */ private void doDispatcherServlet(HttpServletRequest request, HttpServletResponse response) { invoke(request, response); } private void invoke(HttpServletRequest request, HttpServletResponse response) { String queryUrl = request.getRequestURI(); queryUrl = queryUrl.replaceAll("/+", "/"); Method method = handlerMapping.get(queryUrl); if (null == method) { PrintWriter pw = null; try { response.setStatus(404); logger.debug("request fail(404)： " + request.getRequestURI()); pw = response.getWriter(); pw.print("404 not find -> " + request.getRequestURI()); pw.flush(); } catch (IOException e) { e.printStackTrace(); } finally { pw.close(); } } else { //todo method parameters need to deal Object[] paramValues = getMethodParamAndValue(request, response, method); try { String controllerClassName = toFirstWordLower(method.getDeclaringClass().getSimpleName()); Object object = method.invoke(ioc.get(controllerClassName), paramValues); if (object != null) { if (method.isAnnotationPresent(MyResponseBody.class)) { response.setHeader("content-type", "application/json;charset=UTF-8"); if (null == responseBodyHandler) { object = JSONObject.toJSONString(object, SerializerFeature.WriteMapNullValue); } else { object = responseBodyHandler.equals(object); } } response.getWriter().print(object); logger.debug("request-> " + request.getRequestURI() + ", response success ->" + response.getStatus()); } } catch (IllegalAccessException e) { e.printStackTrace(); } catch (InvocationTargetException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } } /**** * @MyRequestParam * 参数解析 复制 * @注意: 参数解析暂不完整 int float long double boolean string * 实体接收暂不支持 * @param request * @param response * @param method * @return */ private Object[] getMethodParamAndValue(HttpServletRequest request, HttpServletResponse response, Method method) { Parameter[] parameters = method.getParameters(); Object[] paramValues = new Object[parameters.length]; for (int i = 0; i < parameters.length; i++) { if (ServletRequest.class.isAssignableFrom(parameters[i].getType())) { paramValues[i] = request; } else if (ServletResponse.class.isAssignableFrom(parameters[i].getType())) { paramValues[i] = response; } else { String bindingValue = parameters[i].getName(); if (parameters[i].isAnnotationPresent(MyRequestParam.class)) { bindingValue = parameters[i].getAnnotation(MyRequestParam.class).value(); } String paramValue = request.getParameter(bindingValue); paramValues[i] = paramValue; if (paramValue != null) { if (Integer.class.isAssignableFrom(parameters[i].getType())) { paramValues[i] = Integer.parseInt(paramValue); } else if (Float.class.isAssignableFrom(parameters[i].getType())) { paramValues[i] = Float.parseFloat(paramValue); } else if (Double.class.isAssignableFrom(parameters[i].getType())) { paramValues[i] = Double.parseDouble(paramValue); } else if (Long.class.isAssignableFrom(parameters[i].getType())) { paramValues[i] = Long.parseLong(paramValue); } else if (Boolean.class.isAssignableFrom(parameters[i].getType())) { paramValues[i] = Boolean.parseBoolean(paramValue); } } } } return paramValues; } /**** * 初始化 * @param contextConfigLocation * @throws Exception */ private void initMyDispatcherServlet(String contextConfigLocation) throws Exception { logger.info("-----------------------------mySpring init start-----------------------------------------"); logger.debug("doLoadConfig:" + contextConfigLocation); //加载配置 doLoadConfig(contextConfigLocation); //扫描 包扫描 logger.debug("scan:" + contextConfig.getProperty("scan.package")); doScanner(contextConfig.getProperty("scan.package")); //创建实体类、ioc doInstance(); //注入 di doAutowired(); //url 映射 initHandlerMapping(); } /*** * 注入 */ private void doAutowired() { if (ioc.isEmpty()) { return; } for (Map.Entry<String, Object> entry : ioc.entrySet()) { Object object = entry.getValue(); Field[] fields = object.getClass().getDeclaredFields(); for (Field filed : fields) { if (filed.isAnnotationPresent(MyAutowired.class)) { MyAutowired myAutowired = filed.getAnnotation(MyAutowired.class); String key = filed.getType().getName(); String val = myAutowired.value(); if (val != null && "".equals(val.trim())) { key = val.trim(); } filed.setAccessible(true); try { filed.set(object, ioc.get(key)); } catch (IllegalAccessException e) { e.printStackTrace(); } } else { continue; } } } } /*** * 初始化HandlerMapper */ private void initHandlerMapping() { if (ioc.isEmpty()) { return; } for (Map.Entry<String, Object> entry : ioc.entrySet()) { Object object = entry.getValue(); Class<?> clazz = object.getClass(); if (clazz.isAnnotationPresent(MyController.class)) { Method[] methods = clazz.getDeclaredMethods(); MyRequestMapping requestMapping = clazz.getAnnotation(MyRequestMapping.class); String crlRequstMapping = requestMapping.value() == null ? "" : requestMapping.value(); for (Method method : methods) { if (method.isAnnotationPresent(MyRequestMapping.class)) { String url = ("/" + crlRequstMapping + "/" + method.getAnnotation(MyRequestMapping.class).value()).replaceAll("/+", "/"); // check request url must only if (handlerMapping.containsKey(url)) { logger.error("mapping request url:" + url + "is already exist! request url must only"); new Exception("mapping:" + url + "is already exist!"); } handlerMapping.put(url, method); logger.debug("mapping: " + url); } else { continue; } } } } } /*** * 加载配置文件 * @param contextConfigLocation * @throws Exception */ private void doLoadConfig(String contextConfigLocation) throws Exception { InputStream is = this.getClass().getClassLoader().getResourceAsStream(contextConfigLocation); if (is == null) { logger.error("config:" + contextConfigLocation + " not exist"); throw new Exception("config:" + contextConfigLocation + " not exist"); } else { try { contextConfig.load(is); } catch (IOException e) { e.printStackTrace(); } finally { //关流 if (null != is) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } } } } /**** * 包扫描 * @param packageName * @throws Exception */ private void doScanner(String packageName) throws Exception { if (packageName == null || packageName.length() == 0) { throw new Exception("init scan is empty"); } URL url = this.getClass().getClassLoader().getResource("/" + packageName.replaceAll("\\.", "/")); if (null != url) { 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", ""); logger.debug("scan class find:" + className); classNames.add(className); } } } } /**** * ioc实例化 */ private void doInstance() { if (classNames.isEmpty()) { return; } for (String className : classNames) { try { // @MyController instance Class<?> clazz = Class.forName(className); if (clazz.isAnnotationPresent(MyController.class)) { logger.debug("MyController instance: " + clazz.getName()); ioc.put(toFirstWordLower(clazz.getSimpleName()), clazz.newInstance()); } else if (clazz.isAnnotationPresent(MyService.class)) { //todo @MyService instance // 1 以自己本类或者用户自定义别名为key Object newInstance = clazz.newInstance(); String key = toFirstWordLower(clazz.getSimpleName()); logger.debug("MyService instance: " + clazz.getName()); MyService service = clazz.getAnnotation(MyService.class); String value = service.value().trim(); if (!"".equals(value)) { key = value; } if (!ioc.containsKey(key)) { ioc.put(key, newInstance); } else { logger.error("MyService instance: " + service.value() + " is exist"); throw new Exception("MyService instance: " + service.value() + " is exist"); } //2 以所继承的接口为 key Class<?>[] interfaces = clazz.getInterfaces(); for (Class<?> interClazz : interfaces) { ioc.put(interClazz.getName(), clazz.newInstance()); } } else if (clazz.isAnnotationPresent(MyResponseAdvice.class)) { if (clazz.isAssignableFrom(ResponseBodyHandler.class)) { if (null != responseBodyHandler) { continue; } responseBodyHandler = (ResponseBodyHandler) clazz.newInstance(); } else { logger.error("class+'" + clazz.getName() + "' must implement ResponseBodyHandler"); throw new Exception("class+'" + clazz.getName() + "' must implement ResponseBodyHandler"); } } else { continue; } } catch (Exception e) { e.printStackTrace(); continue; } } } /** * 把字符串的首字母小写 * * @param name * @return */ private String toFirstWordLower(String name) { char[] charArray = name.toCharArray(); charArray[0] += 32; return String.valueOf(charArray); } }
TestController:
import cn.lyh.mySpring.annotation.*; import cn.lyh.mySpringTest.domain.User; import cn.lyh.mySpringTest.service.TestService; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; import java.util.*; @MyController @MyRequestMapping("/test") public class TestController { @MyAutowired private TestService testService; @MyRequestMapping("test1") public String test1(@MyRequestParam("name") String name, @MyRequestParam("sex") Integer sex, HttpServletRequest request, HttpServletResponse response) throws IOException { return "name=" + name + "sex=" + sex; } @MyRequestMapping("test2") public void test2() { } @MyRequestMapping("test3") @MyResponseBody public Map<String, Object> test3(@MyRequestParam("name") String name, @MyRequestParam("sex") Integer sex, HttpServletRequest request, HttpServletResponse response) throws IOException { Map<String, Object> result = new HashMap<>(); result.put("name", name); result.put("sex", name); return result; } @MyRequestMapping("test4") @MyResponseBody public User test4(@MyRequestParam("name") String name, @MyRequestParam("sex") Integer sex, HttpServletRequest request, HttpServletResponse response) throws IOException { User user = new User(); user.setName(name); user.setId(sex); return user; } @MyRequestMapping("test5") @MyResponseBody public List test5(@MyRequestParam("name") String name, @MyRequestParam("sex") Integer sex, HttpServletRequest request, HttpServletResponse response) throws IOException { List list = new ArrayList(); User user = new User(); user.setName(name); user.setId(sex); list.add(user); return list; } @MyRequestMapping("test6") @MyResponseBody public List test5(HttpServletRequest request, HttpServletResponse response) throws IOException { List list = new ArrayList(); User user = new User(); user.setName(null); user.setId(1); list.add(user); return list; } }
pom文件依赖：
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.6.6</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.7.2</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.47</version>
<scope>compile</scope>
</dependency>
最后附上源码地址(MySpring Moudle)
