基于Servelet手写实现Spring MVC V1.0
1.自定义注解:
package com.yzf.demo.mvcframework.annotation;
import java.lang.annotation.*;
/**
* Created by 于占峰 on 2020/3/30/030.
* 自动注入注解
*/
@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface YZFAutowired {
String value() default "";
}
package com.yzf.demo.mvcframework.annotation;
import java.lang.annotation.*;
/**
* Created by 于占峰 on 2020/3/30/030.
* 控制层注解
*/
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface YZFController {
String value() default "";
}
package com.yzf.demo.mvcframework.annotation;
import java.lang.annotation.*;
/**
* Created by 于占峰 on 2020/3/30/030.
* 请求注解
*/
@Target({ElementType.TYPE,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface YZFRequestMapping {
String value() default "";
}
package com.yzf.demo.mvcframework.annotation;
import java.lang.annotation.*;
/**
* Created by 于占峰 on 2020/3/30/030.
* 参数注解
*/
@Target({ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface YZFRequestParam {
String value() default "";
}
package com.yzf.demo.mvcframework.annotation;
import java.lang.annotation.*;
/**
* Created by 于占峰 on 2020/3/30/030.
* service层注解
*/
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface YZFService {
String value() default "";
}
2.Bean
package com.yzf.demo.mvcframework.controller;
import com.yzf.demo.mvcframework.annotation.YZFAutowired;
import com.yzf.demo.mvcframework.annotation.YZFController;
import com.yzf.demo.mvcframework.annotation.YZFRequestMapping;
import com.yzf.demo.mvcframework.annotation.YZFRequestParam;
import com.yzf.demo.mvcframework.service.IDemoService;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
* Created by 于占峰 on 2020/3/30/030.
*/
@YZFController
@YZFRequestMapping("/demo")
public class DemoController {
@YZFAutowired
private IDemoService demoService;
@YZFRequestMapping("/select")
public void query(HttpServletRequest req, HttpServletResponse resp,@YZFRequestParam("key")String key){
try {
resp.getWriter().write(demoService.query(key));
} catch (IOException e) {
e.printStackTrace();
}
}
@YZFRequestMapping("/add")
public void add(HttpServletRequest req, HttpServletResponse resp,@YZFRequestParam("key")String key){
try {
resp.getWriter().write(demoService.add(key));
} catch (IOException e) {
e.printStackTrace();
}
}
@YZFRequestMapping("/update")
public void update(HttpServletRequest req, HttpServletResponse resp,@YZFRequestParam("key")String key){
try {
resp.getWriter().write(demoService.update(key));
} catch (IOException e) {
e.printStackTrace();
}
}
@YZFRequestMapping("/remove")
public void remove(HttpServletRequest req, HttpServletResponse resp,@YZFRequestParam("key")String key){
try {
resp.getWriter().write(demoService.remove(key));
} catch (IOException e) {
e.printStackTrace();
}
}
}
/**
* Created by 于占峰 on 2020/3/30/030.
*/
@YZFService
public class DeserviceImpl implements IDemoService {
@Override
public String query(String value) {
return "SUCCESS:"+value;
}
@Override
public String add(String value) {
return "SUCCESS:"+value;
}
@Override
public String update(String value) {
return "SUCCESS:"+value;
}
@Override
public String remove(String value) {
return "SUCCESS:"+value;
}
}
/**
* Created by 于占峰 on 2020/3/30/030.
*/
public interface IDemoService {
public String query(String value);
public String add(String value);
public String update(String value);
public String remove(String value);
}
3.核心功能实现代码
package com.yzf.demo.mvcframework.v1.servlet;
import com.yzf.demo.mvcframework.annotation.*;
import javax.servlet.ServletConfig;
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.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.net.URL;
import java.util.*;
/**
* Created by 于占峰 on 2020/3/30/030.
* 手写实现Spring MVC 流程 V1.0
*/
public class YZFDispatchServlet extends HttpServlet {
//Properties文件对象
private Properties contextConfig = new Properties();
//用于装入所有类名
private List<String> classNames = new ArrayList<String>();
//IoC容器
private Map<String, Object> ioc = new HashMap<String, Object>();
//存储URL和方法的handlerMapping
private Map<String, Method> handlerMapping = new HashMap<String, Method>();
@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 {
// 根据URL寻找对应的Method 并通过HttpServletResponse返回结果
doDispath(req, resp);
} catch (Exception e) {
e.printStackTrace();
resp.getWriter().write("500 服务器发生异常" + Arrays.toString(e.getStackTrace()));
}
}
private void doDispath(HttpServletRequest req, HttpServletResponse resp) throws Exception {
String url = req.getRequestURI();
String contextPath = req.getContextPath();
url = url.replace(contextPath, "").replace("/+", "/");
//如果不存在该请求路径则抛出页面找不到异常
if (!this.handlerMapping.containsKey(url)) {
resp.getWriter().write("404 Not Found!!!");
}
Map<String, String[]> params = req.getParameterMap();
Method method = this.handlerMapping.get(url);
//处理形参
//方法的形参
System.out.println(url + "-------------------------------------------");
System.out.println(method + "--------------------------------------------");
Class<?>[] parameterTypes = method.getParameterTypes();
Object[] paramValues = new Object[parameterTypes.length];
for (int i = 0; i < parameterTypes.length; i++) {
Class paramterType = parameterTypes[i];
if (paramterType == HttpServletRequest.class) {
paramValues[i] = req;
} else if (paramterType == HttpServletResponse.class) {
paramValues[i] = resp;
} else if (paramterType == String.class) {
Annotation[][] pa = method.getParameterAnnotations();
for (int j = 0; j < pa.length; j++) {
for (Annotation annotations : pa[i]) {
if (annotations instanceof YZFRequestParam) {
String paramName = ((YZFRequestParam) annotations).value();
if (!"".equals(paramName.trim())) {
String value = Arrays.toString(params.get(paramName))
.replace("\\[|\\]", "")
.replace("\\s+", ",");
paramValues[i] = value;
}
}
}
}
}
}
String beanName = toLowerFirstCase(method.getDeclaringClass().getSimpleName());
for (Map.Entry<String, Object> entry : ioc.entrySet()) {
System.out.println(entry.getKey() + "++++++++++++++++++++++++++++++++++++");
System.out.println(entry.getValue());
}
System.err.println(beanName + "----------------------");
System.err.println(ioc.get(beanName) + "----------------------");
System.err.println(paramValues + "----------------------");
method.invoke(ioc.get(beanName), paramValues);
}
@Override
public void init(ServletConfig config) throws ServletException {
//1.加载配置文件
doLoadConfig(config.getInitParameter("contextConfigLocation"));
//2.扫描相关类
doScanner(contextConfig.getProperty("scanPackage"));
//3.初始化IoC容器,将扫描到的相关类实例化,装入IoC
doInstance();
//4.完成依赖注入
doAutowired();
//5.初始化HandlerMapping
doInitHandlerMapping();
System.err.println("初始化启动完成:"
+ ioc.size()
+ handlerMapping.size()
);
}
private void doInitHandlerMapping() {
//判断IoC内是否存在Bean
if (ioc.isEmpty()) {
return;
}
for (Map.Entry<String, Object> entry : ioc.entrySet()) {
Class<?> clazz = entry.getValue().getClass();
//如果是控制层则跳过
if (!clazz.isAnnotationPresent(YZFController.class)) {
continue;
}
//获得可能是Controller类YZFRequestMapping注解上的URL
String baseUrl = "";
if (clazz.isAnnotationPresent(YZFRequestMapping.class)) {
YZFRequestMapping requestMapping = clazz.getAnnotation(YZFRequestMapping.class);
baseUrl = requestMapping.value();
}
//反射获得所有的public方法
for (Method method : clazz.getMethods()) {
//如果没有requestMapping注解则跳过
if (!method.isAnnotationPresent(YZFRequestMapping.class)) {
continue;
}
YZFRequestMapping requestMapping = method.getAnnotation(YZFRequestMapping.class);
//拼接完整的请求URL
String url = (baseUrl.replace("/+", "/") + requestMapping.value().replace("/+", "/"));
handlerMapping.put(url, method);
System.err.println("Mapping:" + url + "---" + method + "========");
}
}
}
private void doAutowired() {
//判断IoC内是否存在Bean
if (ioc.isEmpty()) {
return;
}
//迭代所有Bean
for (Map.Entry<String, Object> stringObjectEntry : ioc.entrySet()) {
//取出所有修饰字段 包括私有的
for (Field field : stringObjectEntry.getValue().getClass().getDeclaredFields()) {
//如果当前字段没有存在AutoWired注解则跳过
if (!field.isAnnotationPresent(YZFAutowired.class)) {
continue;
}
//获得注解对象
YZFAutowired yzfAutowired = field.getAnnotation(YZFAutowired.class);
//如果用户没有自定义BeanName,就默认根据类型注入
String beanName = yzfAutowired.value().trim();
if ("".equals(beanName)) {
beanName = field.getType().getName();
}
//设置字段暴力访问
field.setAccessible(true);
//通过接口的全名拿到接口的实现类实例
try {
field.set(stringObjectEntry.getValue(), ioc.get(beanName));
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
}
}
private void doInstance() {
//判断是否取得类名集合
if (classNames.isEmpty()) {
return;
}
//遍历类名集合
for (String className : classNames) {
try {
//得到class对象
System.err.println(className + "=================================================");
Class<?> clazz = Class.forName(className);
//判断是否存在Controller注解
if (clazz.isAnnotationPresent(YZFController.class)) {
//生成key(小写首字母简单类名) value 实例化Bean
String beanName = toLowerFirstCase(clazz.getSimpleName());
Object instance = null;
try {
instance = clazz.newInstance();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
ioc.put(beanName, instance);
} else if (clazz.isAnnotationPresent(YZFService.class)) {
//1. 在多个包下存在相同的类名,只能自己进行全局唯一命名
String beanName = clazz.getAnnotation(YZFService.class).value();
if ("".equals(beanName.trim())) {
beanName = toLowerFirstCase(clazz.getSimpleName());
}
//2.默认的类名首字母小写
Object istance = null;
try {
istance = clazz.newInstance();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
ioc.put(beanName, istance);
//3.如果是接口
//判断有多少个实现类,如果只有一个就默认选择这个实现类 否则抛出异常
for (Class<?> i : clazz.getInterfaces()) {
if (ioc.containsKey(i.getName())) {
try {
throw new Exception(i.getName() + "接口存在多个实现类");
} catch (Exception e) {
e.printStackTrace();
}
}
ioc.put(i.getName(), istance);
}
} else {
//不存在Controller注解
continue;
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
}
private void doScanner(String scanPackage) {
URL url = this.getClass().getClassLoader().getResource("/" + scanPackage.replace(".", "/"));
File classPath = new File(url.getFile());
//迭代文件夹
for (File file : classPath.listFiles()) {
//短短是否为文件夹 是则继续迭代
if (file.isDirectory()) {
doScanner(scanPackage + "." + file.getName());
} else {
//判断是否为.class结尾的文件
if (!file.getName().endsWith(".class")) {
continue;
}
//取得全类名
String className = (scanPackage + "." + file.getName().replace(".class", ""));
classNames.add(className);
}
}
}
private void doLoadConfig(String contextConfigLocation) {
//获得流
InputStream is = this.getClass().getClassLoader().getResourceAsStream(contextConfigLocation);
try {
//加载读取配置文件
contextConfig.load(is);
} catch (IOException e) {
e.printStackTrace();
} finally {
if (null != is) {
try {
//关闭流
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
/**
* 首字母转小写
*
* @param simpleName
* @return
*/
private String toLowerFirstCase(String simpleName) {
char[] chars = simpleName.toCharArray();
chars[0] += 32;
return String.valueOf(chars);
}
}
4.pom依赖
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>servlet-api</artifactId>
<version>2.4</version>
<scope>provided</scope>
</dependency>
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