Java Web
笔记来源
Maven配置
官网
配置环境变量
%MAVEN_HOME%\bin MAVEN_HOME为maven的目录
镜像
maven目录下的conf/settings.xml 大约147行
nexus-aliyun
*,!jeecg,!jeecg-snapshots
Nexus aliyun
http://maven.aliyun.com/nexus/content/groups/public
本地仓库
maven目录下的conf/settings.xm 大约55行
maven目录\maven-repo
配置文件，无法被导出或者生效的问题
<build>
<resources>
<resource>
<directory>src/main/resourcesdirectory>
<includes>
<include>**/*.propertiesinclude>
<include>**/*.xmlinclude>
includes>
<filtering>truefiltering>
resource>
<resource>
<directory>src/main/javadirectory>
<includes>
<include>**/*.propertiesinclude>
<include>**/*.xmlinclude>
includes>
<filtering>truefiltering>
resource>
resources>
build>
将web.xml版本配置成和tomcat一致
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0"
metadata-complete="true">
web-app>
Maven仓库的使用
地址
Servelet
Hello Servelet
public class HelloServlet extends HttpServlet {
//由于get或者post只是请求实现的不同的方式，可以相互调用，业务逻辑都一样；
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//ServletOutputStream outputStream = resp.getOutputStream();
PrintWriter writer = resp.getWriter(); //响应流
writer.print("Hello,Serlvet");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
<servlet>
<servlet-name>helloservlet-name>
<servlet-class>com.kuang.servlet.HelloServletservlet-class>
servlet>
<servlet-mapping>
<servlet-name>helloservlet-name>
<url-pattern>/hellourl-pattern>
servlet-mapping>
Mapping问题
- 一个Servlet可以指定一个映射路径
- 一个Servlet可以指定多个映射路径
- 一个Servlet可以指定通用映射路径
<servlet-mapping>
<servlet-name>helloservlet-name>
<url-pattern>/hello/*url-pattern>
servlet-mapping>
- 设置Servelet为默认请求路径
<servlet-mapping>
<servlet-name>helloservlet-name>
<url-pattern>/*url-pattern>
servlet-mapping>
-
指定一些后缀或者前缀等等….
<servlet-mapping> <servlet-name>helloservlet-name> <url-pattern>*.qinjiangurl-pattern> servlet-mapping> -
优先级问题
指定了固有的映射路径优先级最高，如果找不到就会走默认的处理请求；
ServletContext
web容器在启动的时候，它会为每个web程序都创建一个对应的ServletContext对象，它代表了当前的web应用；
共享数据
我在这个Servlet中保存的数据，可以在另外一个servlet中拿到；
public class HelloServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//this.getInitParameter() 初始化参数
//this.getServletConfig() Servlet配置
//this.getServletContext() Servlet上下文
ServletContext context = this.getServletContext();
String username = "zz"; //数据
context.setAttribute("username",username); //将一个数据保存在了ServletContext中
}
}
public class GetServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
ServletContext context = this.getServletContext();
String username = (String) context.getAttribute("username");
resp.setContentType("text/html"); //设置响应的页面类型
resp.setCharacterEncoding("utf-8");
resp.getWriter().print("名字"+username);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
<servlet>
<servlet-name>helloservlet-name>
<servlet-class>com.zz.servlet.HelloServletservlet-class>
servlet>
<servlet-mapping>
<servlet-name>helloservlet-name>
<url-pattern>/hellourl-pattern>
servlet-mapping>
<servlet>
<servlet-name>getcservlet-name>
<servlet-class>com.zz.servlet.GetServletservlet-class>
servlet>
<servlet-mapping>
<servlet-name>getcservlet-name>
<url-pattern>/getcurl-pattern>
servlet-mapping>
获取初始化参数
<context-param>
<param-name>urlparam-name>
<param-value>jdbc:mysql://localhost:3306/mybatisparam-value>
context-param>
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
ServletContext context = this.getServletContext();
String url = context.getInitParameter("url");
resp.getWriter().print(url);
}
请求转发
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
ServletContext context = this.getServletContext();
//RequestDispatcher requestDispatcher = context.getRequestDispatcher("/gp"); //转发的请求路径
//requestDispatcher.forward(req,resp); //调用forward实现请求转发；
context.getRequestDispatcher("/gp").forward(req,resp); //相当于商人
}
<%--前端方式--%>
<% pageContext.forward("xx.jsp") %>
对比HttpServletResponse实现重定向（指路人)
```java
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
/*
resp.setHeader("Location","/r/img");
resp.setStatus(302);
*/
resp.sendRedirect("/r/img");//重定向
}
读取资源文件
public class ServletDemo05 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse response) throws ServletException, IOException {
InputStream resourceAsStream = this.getServletContext().getResourceAsStream("/WEB-INF/classes/db.properties");
Properties properties = new Properties();
properties.load(resourceAsStream);
String name = properties.getProperty("name");
response.getWriter().print(name);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
HttpServletResponse
下载文件
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// 1. 要获取下载文件的路径
String realPath = "我的路径\servlet-01\src\main\resources\1.png";
// 2. 下载的文件名是啥？
String fileName = realPath.substring(realPath.lastIndexOf("\\") + 1);
// 3. 设置想办法让浏览器能够支持(Content-Disposition)下载我们需要的东西,中文文件名URLEncoder.encode编码，否则有可能乱码
resp.setHeader("Content-Disposition","attachment;filename="+URLEncoder.encode(fileName,"UTF-8"));
// 4. 获取下载文件的输入流
FileInputStream in = new FileInputStream(realPath);
// 5. 创建缓冲区
int len = 0;
byte[] buffer = new byte[1024];
// 6. 获取OutputStream对象
ServletOutputStream out = resp.getOutputStream();
// 7. 将FileOutputStream流写入到buffer缓冲区,使用OutputStream将缓冲区中的数据输出到客户端！
while ((len=in.read(buffer))>0){ // 如果in从缓冲区读取数据大于0 继续执行
out.write(buffer,0,len);
}
in.close();
out.close();
}
简单实现登录重定向
<%--这里提交的路径，需要寻找到项目的路径--%>
<%--${pageContext.request.contextPath}代表当前的项目--%>
<form action="${pageContext.request.contextPath}/login" method="get">
用户名：<input type="text" name="username"> <br>
密码：<input type="password" name="password"> <br>
<input type="submit">
form>
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//处理请求
String username = req.getParameter("username");
String password = req.getParameter("password");
System.out.println(username+":"+password);
//重定向时候一定要注意，路径问题，否则404；
resp.sendRedirect("/r/success.jsp"); //跳转到成功页面
}
HttpServletRequest
获取参数，请求转发
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Titletitle>
head>
<body>
<h1>loginh1>
<div>
<form action="${pageContext.request.contextPath}/login" method="post">
用户名：<input type="text" name="username"> <br>
密码：<input type="password" name="password"> <br>
爱好
<input type="checkbox" name="hobbys" value="girls">girls
<input type="checkbox" name="hobbys" value="code">code
<input type="checkbox" name="hobbys" value="book">book
<input type="checkbox" name="hobbys" value="movie">movie
<input type="submit">
<br>
form>
div>
body>
html>
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("utf-8");
resp.setCharacterEncoding("utf-8");
String username = req.getParameter("username");
String password = req.getParameter("password");
String[] hobbys = req.getParameterValues("hobbys");
System.out.println("=============================");
//后台接收中文乱码问题
System.out.println(username);
System.out.println(password);
System.out.println(Arrays.toString(hobbys));
System.out.println("=============================");
System.out.println(req.getContextPath());
//通过请求转发
//这里的 / 代表当前的web应用
req.getRequestDispatcher("/success.jsp").forward(req,resp);
}
Session
使用Session：
public class SessionDemo01 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//解决乱码问题
req.setCharacterEncoding("UTF-8");
resp.setCharacterEncoding("UTF-8");
resp.setContentType("text/html;charset=utf-8");
HttpSession session = req.getSession(); //得到Session
session.setAttribute("name",new Person("zhangyan",20)); //给Session中存东西
String id = session.getId(); //获取Session的ID
//Session创建的时候做了什么事情；
// Cookie cookie = new Cookie("JSESSIONID",id);
// resp.addCookie(cookie);
Person me = (Person) session.getAttribute("name"); //得到Session
if(session.isNew()){ //判断Session是不是新创建
resp.getWriter().print("session create sucess:"+id);
resp.getWriter().print("
");
resp.getWriter().print("
");
resp.getWriter().print(me.toString());
}else {
resp.getWriter().print("session have been exist:"+id);
resp.getWriter().print("
");
resp.getWriter().print("
");
resp.getWriter().print(me.toString());
}
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
public class SessionDemo02 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
HttpSession session = req.getSession();
session.removeAttribute("name"); //移除属性
session.invalidate(); //手动注销Session
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
会话自动过期：web.xml配置
<session-config>
<session-timeout>15session-timeout>
session-config>
JSP
<% 代码片段 代码在方法里面 %>
<%= 变量或者表达式%>
<%! 声明 代码在方法之外%>
<%--注释--%>
JSP指令
定制错误页面
<%@page errorPage=" " %>
第二种方法
<error-page>
<error-code>500error-code>
<location>/error/error.jsplocation>
error-page>
引用页面
<%@page args.... %>
<%@include file=""%>
<%--@include会将两个页面合二为一--%>
<%@include file="common/header.jsp"%>
<h1>total</h1>
<%@include file="common/footer.jsp"%>
<hr>
<%--本质上是这个
out.write(" l am head
\r\n");
out.write("\r\n");
int i = 10 ;
out.write('\r');
out.write('\n');
out.print(i);
out.write("\n");
out.write("total
\n");
out.write("\r\n");
out.write("\r\n");
out.write("l am footer
");
--%>
<%--jSP标签
jsp:include：拼接页面，本质还是三个 page代表页面 页面是要当前web下的页面 所以前面需要加个/
--%>
<jsp:include page="/common/header.jsp"/>
<h1>网页主体</h1>
<jsp:include page="/common/footer.jsp"/>
<%--本质上是这个
org.apache.jasper.runtime.JspRuntimeLibrary.include(request, response, "/common/header.jsp", out, false);
out.write("\n");
out.write("total2
\n");
out.write('\n');
out.print(i);
out.write('\n');
org.apache.jasper.runtime.JspRuntimeLibrary.include(request, response, "/common/footer.jsp", out, false);
--%>
内置对象
pageContext.setAttribute("name1","zz"); //保存的数据只在一个页面中有效
request.setAttribute("name2","zz"); //保存的数据只在一次请求中有效，请求转发会携带这个数据
session.setAttribute("name3","zz"); //保存的数据只在一次会话中有效，从打开浏览器到关闭浏览器
application.setAttribute("name4","zz"); //保存的数据只在服务器中有效，从打开服务器到关闭服务器
request：客户端向服务器发送请求，产生的数据，用户看完就没用了，比如：新闻，用户看完没用的！
session：客户端向服务器发送请求，产生的数据，用户用完一会还有用，比如：购物车；
application：客户端向服务器发送请求，产生的数据，一个用户用完了，其他用户还可能使用，比如：聊天数据；
JavaBean
JavaBean有特定的写法：
- 必须要有一个无参构造
- 属性必须私有化
- 必须有对应的get/set方法；
class People{
private int id;
private String name;
private int id;
private String address;
}
class A{
new People(1,"zz",3，"shanghai");
new People(2,"zz",3，"shanghai");
new People(3,"zz",3，"shanghai");
}
操作数据库里的东西
<%
People people = new People();
people.setId(1);
people.setName("zy");
people.setAge(20);
people.setAddress("shanghai");
%>
name <%=people.getId()%>
id <%=people.getName()%>
age <%=people.getAge()%>
address <%=people.getAddress()%>
等价于
<jsp:useBean id="people" class="zhang.People" scope="page"/>
<jsp:setProperty name="people" property="id" value="1"/>
<jsp:setProperty name="people" property="name" value="zy"/>
<jsp:setProperty name="people" property="age" value="20"/>
<jsp:setProperty name="people" property="address" value="shanghai"/>
name <jsp:getProperty name="people" property="name"/>
id <jsp:getProperty name="people" property="id"/>
age <jsp:getProperty name="people" property="age"/>
address <jsp:getProperty name="people" property="address"/>
Filter
public class CharacterEncodingFilter implements Filter {
//初始化：web服务器启动，就以及初始化了，随时等待过滤对象出现！
public void init(FilterConfig filterConfig) throws ServletException {
System.out.println("CharacterEncodingFilter初始化");
}
//Chain : 链
/*
1. 过滤中的所有代码，在过滤特定请求的时候都会执行
2. 必须要让过滤器继续同行
chain.doFilter(request,response);
*/
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=UTF-8");
System.out.println("CharacterEncodingFilter执行前....");
chain.doFilter(request,response); //让我们的请求继续走，如果不写，程序到这里就被拦截停止！相当于转接人
System.out.println("CharacterEncodingFilter执行后....");
}
//销毁：web服务器关闭的时候，过滤会销毁
public void destroy() {
System.out.println("CharacterEncodingFilter销毁");
}
}
在web.xml中配置 Filter
<filter>
<filter-name>CharaterEncodingFilterfilter-name>
<filter-class>com.zhang.filter.CharaterEncodingFilterfilter-class>
filter>
<filter-mapping>
<filter-name>CharaterEncodingFilterfilter-name>
<url-pattern>/servelet/*url-pattern>
filter-mapping>
监听器
<h1>当前在线人数
<span>
<%=
this.getServletConfig().getServletContext().getAttribute("Online")
%>
span>
h1>
//统计网站在线人数 ： 统计session
public class OnlineCountListener implements HttpSessionListener {
//创建session监听： 看你的一举一动
//一旦创建Session就会触发一次这个事件！
public void sessionCreated(HttpSessionEvent se) {
ServletContext ctx = se.getSession().getServletContext();
System.out.println(se.getSession().getId());
Integer onlineCount = (Integer) ctx.getAttribute("OnlineCount");
if (onlineCount==null){
onlineCount = new Integer(1);
}else {
int count = onlineCount.intValue();
onlineCount = new Integer(count+1);
}
ctx.setAttribute("OnlineCount",onlineCount);
}
//销毁session监听
//一旦销毁Session就会触发一次这个事件！
public void sessionDestroyed(HttpSessionEvent se) {
ServletContext ctx = se.getSession().getServletContext();
Integer onlineCount = (Integer) ctx.getAttribute("OnlineCount");
if (onlineCount==null){
onlineCount = new Integer(0);
}else {
int count = onlineCount.intValue();
onlineCount = new Integer(count-1);
}
ctx.setAttribute("OnlineCount",onlineCount);
}
/*
Session销毁：
1. 手动销毁 getSession().invalidate();
2. 自动销毁
*/
}
<listener>
<listener-class>com.zhang.listener.OnlineCountListenerlistener-class>
listener>
<session-config>
<session-timeout>1session-timeout>
session-config>
简单登录
登录页面
<form action="/login" method="post">
name:
<input type="text" name="username">
<input type="submit" value="submit">
form>
Sucess and Error
<%--Sucess --%>
<%--可以但不应该交给jsp来做、交给过滤器--%>
<%--
<%
Object userSession = request.getSession().getAttribute("user_session");
if(userSession==null){ <%--userSession为空重定向到login.jsp页面 --%>
response.sendRedirect("/login.jsp");
}
%>
--%>
<h1>congratulation sucess</h1>
<a href="/loginout">loginout</a>
<%--error--%>
<h1>you are wrong</h1>
<a href="/login.jsp">back</a>
LoginServlet
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String username = req.getParameter("username");
if(username.equals("zz")){
req.getSession().setAttribute("user_session",req.getSession().getId());
resp.sendRedirect("/Sucess/sucess.jsp");
}else {
resp.sendRedirect("/error.jsp");
}
}
Loginout
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
Object user_session = req.getSession().getAttribute("user_session");
if(user_session!=null){
req.getSession().removeAttribute("user_session"); //移除user_session
resp.sendRedirect("/login.jsp");
}else {
resp.sendRedirect("/login.jsp");
}
}
SysFilter
public void doFilter(ServletRequest req, ServletResponse resp, FilterChain filterChain) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest) req;
HttpServletResponse response = (HttpServletResponse) resp;
if(request.getSession().getAttribute("user_session")==null){
response.sendRedirect("/error.jsp");
}
filterChain.doFilter(req,resp);
}
xml
<servlet>
<servlet-name>loginservlet-name>
<servlet-class>com.zhang.login.LoginServletservlet-class>
servlet>
<servlet-mapping>
<servlet-name>loginservlet-name>
<url-pattern>/loginurl-pattern>
servlet-mapping>
<servlet>
<servlet-name>loginoutservlet-name>
<servlet-class>com.zhang.loginout.LoginOutservlet-class>
servlet>
<servlet-mapping>
<servlet-name>loginoutservlet-name>
<url-pattern>/loginouturl-pattern>
servlet-mapping>
<filter>
<filter-name>SysFilterfilter-name>
<filter-class>com.zhang.filter.SysFilterfilter-class>
filter>
<filter-mapping>
<filter-name>SysFilterfilter-name>
<url-pattern>/Sucess/*url-pattern>
filter-mapping>
JDBC
JDBC 固定步骤：
- 加载驱动
- 连接数据库,代表数据库
- 向数据库发送SQL的对象Statement : CRUD
- 编写SQL （根据业务，不同的SQL）
- 执行SQL
- 关闭连接
public class TestJdbc {
public static void main(String[] args) throws ClassNotFoundException, SQLException {
//配置信息
//useUnicode=true&characterEncoding=utf-8 解决中文乱码
String url ="jdbc:mysql://localhost:3306/jdbc?useSSL=false&serverTimezone=UTC" +
"&useUnicode=true&characterEncoding=utf-8";
String username = "root";
String password = "1234";
//1.加载驱动
Class.forName("com.mysql.jdbc.Driver");
//2.连接数据库,代表数据库
Connection connection = DriverManager.getConnection(url, username, password);
//3.向数据库发送SQL的对象Statement,PreparedStatement : CRUD
Statement statement = connection.createStatement();
//4.编写SQL
String sql = "select * from users";
//5.执行查询SQL，返回一个 ResultSet ： 结果集
ResultSet rs = statement.executeQuery(sql);
while (rs.next()){
System.out.println("id="+rs.getObject("id"));
System.out.println("name="+rs.getObject("name"));
System.out.println("password="+rs.getObject("password"));
System.out.println("email="+rs.getObject("email"));
System.out.println("birthday="+rs.getObject("birthday"));
}
//6.关闭连接，释放资源（一定要做） 先开后关
rs.close();
statement.close();
connection.close();
}
}
预编译SQL
public class TestJDBC2 {
public static void main(String[] args) throws Exception {
//配置信息
//useUnicode=true&characterEncoding=utf-8 解决中文乱码
String url ="jdbc:mysql://localhost:3306/jdbc?useSSL=false&serverTimezone=UTC" +
"&useUnicode=true&characterEncoding=utf-8";
String username = "root";
String password = "1234";
//1.加载驱动
Class.forName("com.mysql.jdbc.Driver");
//2.连接数据库,代表数据库
Connection connection = DriverManager.getConnection(url, username, password);
//3.编写SQL
String sql = "insert into users(id, name, password, email, birthday) values (?,?,?,?,?);";
//4.预编译
PreparedStatement preparedStatement = connection.prepareStatement(sql);
preparedStatement.setInt(1,2);//给第一个占位符？ 的值赋值为1；
preparedStatement.setString(2,"zz");//给第二个占位符？ 的值赋值为狂神说Java；
preparedStatement.setString(3,"123456");//给第三个占位符？ 的值赋值为123456；
preparedStatement.setString(4,"[email protected]");//给第四个占位符？ 的值赋值为[email protected]
preparedStatement.setDate(5,new Date(new java.util.Date().getTime()));//给第五个占位符？ 的值赋值为new Date(new java.util.Date().getTime())；
//5.执行SQL
int i = preparedStatement.executeUpdate();
if (i>0){
System.out.println("insert sucess");
}
//6.关闭连接，释放资源（一定要做） 先开后关
preparedStatement.close();
connection.close();
}
}
事务
搭建一个环境
CREATE TABLE account(
id INT PRIMARY KEY AUTO_INCREMENT,
`name` VARCHAR(40),
money FLOAT
);
INSERT INTO account(`name`,money) VALUES('A',1000);
INSERT INTO account(`name`,money) VALUES('B',1000);
INSERT INTO account(`name`,money) VALUES('C',1000);
start transaction ;#开启事务
update account set money = money-100 where name='A';
update account set money = money+100 where name='B';
rollback;#回滚 要发生在commit之前才有用
commit;#提交事务
@Test
public void test() {
//配置信息
//useUnicode=true&characterEncoding=utf-8 解决中文乱码
String url="jdbc:mysql://localhost:3306/jdbc?useUnicode=true&characterEncoding=utf-8";
String username = "root";
String password = "1234";
Connection connection = null;
//1.加载驱动
try {
Class.forName("com.mysql.jdbc.Driver");
//2.连接数据库,代表数据库
connection = DriverManager.getConnection(url, username, password);
//3.通知数据库开启事务,false 开启
connection.setAutoCommit(false);
String sql = "update account set money = money-100 where name = 'A'";
connection.prepareStatement(sql).executeUpdate();
//制造错误
//int i = 1/0;
String sql2 = "update account set money = money+100 where name = 'B'";
connection.prepareStatement(sql2).executeUpdate();
connection.commit();//以上两条SQL都执行成功了，就提交事务！
System.out.println("success");
} catch (Exception e) {
try {
//如果出现异常，就通知数据库回滚事务
connection.rollback();
} catch (SQLException e1) {
e1.printStackTrace();
}
e.printStackTrace();
}finally {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
流程
web.xml最新的
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0"
metadata-complete="true">
web-app>
servlet
req.setCharacterEncoding("utf-8");
resp.setCharacterEncoding("utf-8"); //告诉servlet用UTF-8转码
resp.setContentType("text/html;charset=utf-8"); //设置响应的页面类型 让浏览器用utf8来解析返回的数据
<dependency>
<groupId>javax.servletgroupId>
<artifactId>javax.servlet-apiartifactId>
<version>4.0.1version>
<scope>compilescope>
dependency>
<dependency>
<groupId>javax.servlet.jspgroupId>
<artifactId>javax.servlet.jsp-apiartifactId>
<version>2.3.3version>
dependency>
<dependency>
<groupId>javax.servlet.jsp.jstlgroupId>
<artifactId>jstl-apiartifactId>
<version>1.2version>
dependency>
<dependency>
<groupId>taglibsgroupId>
<artifactId>standardartifactId>
<version>1.1.2version>
dependency>
<dependency>
<groupId>mysqlgroupId>
<artifactId>mysql-connector-javaartifactId>
<version>5.1.48version>
dependency>
<dependency>
<groupId>junitgroupId>
<artifactId>junitartifactId>
<version>4.12version>
dependency>
jdbc:mysql://localhost:3306/jdbc?useSSL=false&serverTimezone=UTC