#### 1、Java Web Servlet
src 目录 对应于tomcat 相应应用app下的WEB-INF/classes目录
web目录下的文件对应tomcat 相应应用app下目录文件
httpRequest 请求：
GET /login.html HTTP/1.1请求行
host:www.baidu.com 请求头
请求空行
username=howhy&age=12 请求体
httpResponse 响应：
HTTP/1.1 200 OK 响应行
Content-Type: text/html;charset=utf-8 响应头
响应空行
html json 响应体
```java
//interface Servlet
public interface Servlet {
void init(ServletConfig var1) throws ServletException;//只执行一次 load-on-startup 默认使用时创建若设置为1随tomcat启动而创建
ServletConfig getServletConfig();
void service(ServletRequest var1, ServletResponse var2) throws ServletException, IOException;//业务处理
String getServletInfo();
void destroy();//只执行一次随tomcat关闭而销毁
}
public abstract class GenericServlet implements Servlet, ServletConfig, Serializable {
private static final long serialVersionUID = 1L;
private transient ServletConfig config;
public GenericServlet() {
}
public void destroy() {
}
public String getInitParameter(String name) {
return this.getServletConfig().getInitParameter(name);
}
public Enumeration<String> getInitParameterNames() {
return this.getServletConfig().getInitParameterNames();
}
public ServletConfig getServletConfig() {
return this.config;
}
public ServletContext getServletContext() {
return this.getServletConfig().getServletContext();
}
public String getServletInfo() {
return "";
}
public void init(ServletConfig config) throws ServletException {
this.config = config;
this.init();
}
public void init() throws ServletException {
}
public void log(String msg) {
this.getServletContext().log(this.getServletName() + ": " + msg);
}
public void log(String message, Throwable t) {
this.getServletContext().log(this.getServletName() + ": " + message, t);
}
public abstract void service(ServletRequest var1, ServletResponse var2) throws ServletException, IOException;
public String getServletName() {
return this.config.getServletName();
}
}
public abstract class HttpServlet extends GenericServlet {
private static final long serialVersionUID = 1L;
private static final String METHOD_DELETE = "DELETE";
private static final String METHOD_HEAD = "HEAD";
private static final String METHOD_GET = "GET";
private static final String METHOD_OPTIONS = "OPTIONS";
private static final String METHOD_POST = "POST";
private static final String METHOD_PUT = "PUT";
private static final String METHOD_TRACE = "TRACE";
private static final String HEADER_IFMODSINCE = "If-Modified-Since";
private static final String HEADER_LASTMOD = "Last-Modified";
private static final String LSTRING_FILE = "javax.servlet.http.LocalStrings";
private static ResourceBundle lStrings = ResourceBundle.getBundle("javax.servlet.http.LocalStrings");
public HttpServlet() {
}
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String protocol = req.getProtocol();
String msg = lStrings.getString("http.method_get_not_supported");
if (protocol.endsWith("1.1")) {
resp.sendError(405, msg);
} else {
resp.sendError(400, msg);
}
}
protected long getLastModified(HttpServletRequest req) {
return -1L;
}
protected void doHead(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
if (DispatcherType.INCLUDE.equals(req.getDispatcherType())) {
this.doGet(req, resp);
} else {
NoBodyResponse response = new NoBodyResponse(resp);
this.doGet(req, response);
response.setContentLength();
}
}
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String protocol = req.getProtocol();
String msg = lStrings.getString("http.method_post_not_supported");
if (protocol.endsWith("1.1")) {
resp.sendError(405, msg);
} else {
resp.sendError(400, msg);
}
}
protected void doPut(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String protocol = req.getProtocol();
String msg = lStrings.getString("http.method_put_not_supported");
if (protocol.endsWith("1.1")) {
resp.sendError(405, msg);
} else {
resp.sendError(400, msg);
}
}
protected void doDelete(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String protocol = req.getProtocol();
String msg = lStrings.getString("http.method_delete_not_supported");
if (protocol.endsWith("1.1")) {
resp.sendError(405, msg);
} else {
resp.sendError(400, msg);
}
}
private static Method[] getAllDeclaredMethods(Class<?> c) {
if (c.equals(HttpServlet.class)) {
return null;
} else {
Method[] parentMethods = getAllDeclaredMethods(c.getSuperclass());
Method[] thisMethods = c.getDeclaredMethods();
if (parentMethods != null && parentMethods.length > 0) {
Method[] allMethods = new Method[parentMethods.length + thisMethods.length];
System.arraycopy(parentMethods, 0, allMethods, 0, parentMethods.length);
System.arraycopy(thisMethods, 0, allMethods, parentMethods.length, thisMethods.length);
thisMethods = allMethods;
}
return thisMethods;
}
}
protected void doOptions(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
Method[] methods = getAllDeclaredMethods(this.getClass());
boolean ALLOW_GET = false;
boolean ALLOW_HEAD = false;
boolean ALLOW_POST = false;
boolean ALLOW_PUT = false;
boolean ALLOW_DELETE = false;
boolean ALLOW_TRACE = true;
boolean ALLOW_OPTIONS = true;
for(int i = 0; i < methods.length; ++i) {
Method m = methods[i];
if (m.getName().equals("doGet")) {
ALLOW_GET = true;
ALLOW_HEAD = true;
}
if (m.getName().equals("doPost")) {
ALLOW_POST = true;
}
if (m.getName().equals("doPut")) {
ALLOW_PUT = true;
}
if (m.getName().equals("doDelete")) {
ALLOW_DELETE = true;
}
}
String allow = null;
if (ALLOW_GET) {
allow = "GET";
}
if (ALLOW_HEAD) {
if (allow == null) {
allow = "HEAD";
} else {
allow = allow + ", HEAD";
}
}
if (ALLOW_POST) {
if (allow == null) {
allow = "POST";
} else {
allow = allow + ", POST";
}
}
if (ALLOW_PUT) {
if (allow == null) {
allow = "PUT";
} else {
allow = allow + ", PUT";
}
}
if (ALLOW_DELETE) {
if (allow == null) {
allow = "DELETE";
} else {
allow = allow + ", DELETE";
}
}
if (ALLOW_TRACE) {
if (allow == null) {
allow = "TRACE";
} else {
allow = allow + ", TRACE";
}
}
if (ALLOW_OPTIONS) {
if (allow == null) {
allow = "OPTIONS";
} else {
allow = allow + ", OPTIONS";
}
}
resp.setHeader("Allow", allow);
}
protected void doTrace(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String CRLF = "\r\n";
StringBuilder buffer = (new StringBuilder("TRACE ")).append(req.getRequestURI()).append(" ").append(req.getProtocol());
Enumeration reqHeaderEnum = req.getHeaderNames();
while(reqHeaderEnum.hasMoreElements()) {
String headerName = (String)reqHeaderEnum.nextElement();
buffer.append(CRLF).append(headerName).append(": ").append(req.getHeader(headerName));
}
buffer.append(CRLF);
int responseLength = buffer.length();
resp.setContentType("message/http");
resp.setContentLength(responseLength);
ServletOutputStream out = resp.getOutputStream();
out.print(buffer.toString());
out.close();
}
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String method = req.getMethod();
long lastModified;
if (method.equals("GET")) {
lastModified = this.getLastModified(req);
if (lastModified == -1L) {
this.doGet(req, resp);
} else {
long ifModifiedSince;
try {
ifModifiedSince = req.getDateHeader("If-Modified-Since");
} catch (IllegalArgumentException var9) {
ifModifiedSince = -1L;
}
if (ifModifiedSince < lastModified / 1000L * 1000L) {
this.maybeSetLastModified(resp, lastModified);
this.doGet(req, resp);
} else {
resp.setStatus(304);
}
}
} else if (method.equals("HEAD")) {
lastModified = this.getLastModified(req);
this.maybeSetLastModified(resp, lastModified);
this.doHead(req, resp);
} else if (method.equals("POST")) {
this.doPost(req, resp);
} else if (method.equals("PUT")) {
this.doPut(req, resp);
} else if (method.equals("DELETE")) {
this.doDelete(req, resp);
} else if (method.equals("OPTIONS")) {
this.doOptions(req, resp);
} else if (method.equals("TRACE")) {
this.doTrace(req, resp);
} else {
String errMsg = lStrings.getString("http.method_not_implemented");
Object[] errArgs = new Object[]{method};
errMsg = MessageFormat.format(errMsg, errArgs);
resp.sendError(501, errMsg);
}
}
private void maybeSetLastModified(HttpServletResponse resp, long lastModified) {
if (!resp.containsHeader("Last-Modified")) {
if (lastModified >= 0L) {
resp.setDateHeader("Last-Modified", lastModified);
}
}
}
public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
HttpServletRequest request;
HttpServletResponse response;
try {
request = (HttpServletRequest)req;
response = (HttpServletResponse)res;
} catch (ClassCastException var6) {
throw new ServletException("non-HTTP request or response");
}
this.service(request, response);
}
}
```
```Java
@WebServlet("/demo3")//http://localhost:8081/ServeletDemo2/demo3?name=howhy&age=12
public class ServletDemo3 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println(req);//org.apache.catalina.connector.RequestFacade@68663bec tomcat extends HttpServlet
System.out.println(req.getMethod());//get
System.out.println(req.getContextPath());// /ServeletDemo2
System.out.println(req.getServletPath());// /demo3
System.out.println(req.getPathInfo());
System.out.println(req.getQueryString());// name=howhy&age=12
System.out.println(req.getRequestURI());// /ServeletDemo2/demo3
System.out.println(req.getRequestURL());// http://localhost:8081/ServeletDemo2/demo3
Enumeration<String> headerNames = req.getHeaderNames();
while(headerNames.hasMoreElements()){
System.out.println(headerNames.nextElement());
}
System.out.println(req.getHeader("user-agent"));
resp.getWriter().write("ssssssss");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
super.doPost(req, resp);
}
}
```
##### 1.1转发和重定向
转发：一次请求 只能转发内部路径 可以reqeust域
重定向：两次请求 可以跳转到外部路径 不可以用request域
```
</head>
<body>
<div style="width:300px; height:300px;margin:100px auto">
<img src="/ServeletDemo3/demo2" id="img"/>
<a href="#" id="imga">看不清换一张</a>
</div>
<script>
(function(){
var img=document.getElementById("img");
var imga=document.getElementById("imga");
img.onclick=function(){
img.src="/ServeletDemo3/demo2?t="+new Date().getMilliseconds();
}
imga.onclick=function(){
img.src="/ServeletDemo3/demo2?t="+new Date().getMilliseconds();
}
})()
</script>
</body>
</html>
```
```
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
@WebServlet("/demo2")
public class ServeletDemo2 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
int h=50;
int w=100;
BufferedImage bufferedImage = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
Graphics graphics = bufferedImage.getGraphics();
graphics.setColor(Color.pink);
graphics.fillRect(0,0,w,h);
// graphics.setColor(Color.blue);
// graphics.fillRect(0,0,w-1,h-1);
String azStr="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
Random random = new Random();
for (int i = 0; i < 4; i++) {
int index=random.nextInt(azStr.length());
char code=azStr.charAt(index);
System.out.println(code);
graphics.setColor(Color.blue);
graphics.drawString(code+"",(i+1)*20,25);
}
graphics.setColor(Color.green);
for (int i = 0; i <10 ; i++) {
int x1=random.nextInt(w);
int x2=random.nextInt(w);
int y1=random.nextInt(w);
int y2=random.nextInt(w);
graphics.drawLine(x1,y1,x2,y2);
}
ImageIO.write(bufferedImage,"jpg",resp.getOutputStream());
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("demo2");
this.doGet(req,resp);
}
}
```
```
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<a href="/ServeletDemo3/download?filename=20201201.png">下载1</a>
</body>
</html>
```
```
package com.howhy.controller;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
@WebServlet("/download")
public class DownloadServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("33333333333333333333");
String filename=req.getParameter("filename");
ServletContext servletContext = this.getServletContext();
String mimeType = servletContext.getMimeType(filename);
resp.setContentType(mimeType);
resp.setHeader("content-disposition","attachment;filename="+filename);
String path=servletContext.getRealPath("/img/"+filename);
System.out.println(path);
FileInputStream fileInputStream = new FileInputStream(path);
byte[] buff=new byte[1024];
int len=0;
while((len=fileInputStream.read(buff))!=-1){
resp.getOutputStream().write(buff,0,len);
}
fileInputStream.close();
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doGet(req,resp);
}
}
```
#### 二 jsp
jsp其实就是一个servlet
jsp脚本 <% i=5 %> 这样的代码相当于是在servlet类中的service方法定义 int i=5
<%! i=3 %> 这样的代码相当于是在servlet类中定义的成员变量
<%=i%> 这样的代码相当于是在servlet类中的service输出i的值 为5
jsp内置对象
request response out
```
<%@ page import="com.howhy.controller.User" %>
<%@ page import="java.util.Date" %>
<%@ page import="java.util.ArrayList" %>
<%@ page import="java.util.HashMap" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
<title>el</title>
</head>
<body>
<h4>${4+2}</h4>
<h4>${4-2}</h4>
<h4>${4*2}</h4>
<h4>${4/2}</h4>
<h4>${4%2}</h4>
<h4>${4==2}</h4>
<h4>${4==2 || 1==1}</h4>
<%
request.setAttribute("name","howhy");
session.setAttribute("age",23);
User user = new User();
user.setName("aa");
user.setAge(22);
user.setBirth(new Date());
request.setAttribute("user",user);
ArrayList<Integer> listarr=new ArrayList<Integer>();
listarr.add(2);
listarr.add(21);
listarr.add(22);
request.setAttribute("list",listarr);
HashMap<String, Integer> mp = new HashMap<String, Integer>();
mp.put("zs",12);
mp.put("ls",22);
mp.put("ww",23);
request.setAttribute("users",mp);
request.setAttribute("flag",true);
request.setAttribute("number",3);
%>
<h5>${requestScope.name1}</h5><!--此处取域属性值 也可以直接写${name}会依次从域pageContext request session applicationContext中从小到大查找 找到就不往下找了-->
<h5>${sessionScope.age}</h5>
${user.name}<br/><!--此处取类的属性值类中必须有相应属性的getName方法-->
${user.birth}<br/>
${user.birthStr}<br/>
${requestScope.list}<br/>
${list[0]}<br/>
<c:forEach var="a" items="${list}">
<h4>${a}</h4>
</c:forEach>
${requestScope.users.zs}<br/>
${requestScope.users["ls"]}<br/>
${empty list}<!--emtpy not empty判断字符串 数组 集合 是否为null并且长度为0-->
<c:if test="${flag}">
<h5>this is display</h5>
</c:if><br/>
<c:choose >
<c:when test="${number==1}">星期一</c:when>
<c:when test="${number==2}">星期二</c:when>
<c:when test="${number==3}">星期三</c:when>
<c:when test="${number==4}">星期四</c:when>
<c:when test="${number==5}">星期五</c:when>
<c:when test="${number==6}">星期六</c:when>
<c:when test="${number==7}">星期七</c:when>
<c:otherwise>无效的星期数字</c:otherwise>
</c:choose>
</body>
</html>
```
#### 三 filter
filte url-pattern 特定的url /index.jsp 路径目录/user/* 路径后缀通配符*.jsp 所有 /*
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