​1、防止中文乱码​

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>

request.setCharacterEncoding("UTF-8");
response.setCharacterEncoding("UTF-8");
response.setContentType("text/html; charset=UTF-8");

​2、jsp页面跳转​

request.getRequestDispatcher("./index.jsp").forward(request, response);  //请求转发
response.sendRedirect("error.jsp");  //请求重定向

3、使用servlet注解

@WebServlet("/XXXServlet")

4、jsp获取当前路径

${pageContext.request.contextPath}/xxxx

5、js常用代码

<button onclick="funct1(1)" class="" type="submit"> 确认弹窗</button> <br>
<a class="" href="javascript:funct2(2)">警告弹窗</a> <br>
<a class="" href="javascript:history.back(-1)">返回上一级</a>


<script type="text/javascript">
  function funct1(id){
    if(confirm("确定选择？")){
      window.location.href="${pageContext.request.contextPath}/XXXServlet?method=Confirm&id="+id;
    }
  }
  function funct2(id){
    alert(id)
  }
</script>

6、接收和传递参数

String username = request.getParameter("username"); //可从form表单或者页面对象获取
String password = request.getParameter("password");

request.setAttribute("list", list); //变量、对象和集合都可以存储

7、JSTL标签使用

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>

<c:forEach var="list" items="${list }"> 

        <tr>
          <td>${list.name }</td>
          <td>${list.sex }</td>
          <td>${list.age }</td>
          <td>${list.telphone}</td>
          <td>${list.address }</td>
        </tr>

</c:forEach>

8、CRUD实现步骤

（1）连接数据库 Connection conn = DBUtil.getConnection();

（2）预编译sql语句 PreparedStatement ps = conn.prepareStatement(sql);

（3）查询返回对象 ResultSet rs = ps.executeQuery();

（4）遍历结果，将字段存入对象，再将对象存入list

          while(rs.next()){User user = new User(); user.setName(rs.getString("name")).. list.add(user)} return list

9、Maven配置（mysql、jstl、jsp、servlet）

<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
  <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.47</version>
  </dependency>
  <!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
  <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>3.1.0</version>
      <scope>provided</scope>
  </dependency>
  <!-- https://mvnrepository.com/artifact/javax.servlet.jsp/javax.servlet.jsp-api -->
  <dependency>
      <groupId>javax.servlet.jsp</groupId>
      <artifactId>javax.servlet.jsp-api</artifactId>
      <version>2.3.1</version>
      <scope>provided</scope>
  </dependency>
  <dependency>
    <groupId>jstl</groupId>
    <artifactId>jstl</artifactId>
    <version>1.2</version>
  </dependency>
  <dependency>
    <groupId>taglibs</groupId>
    <artifactId>standard</artifactId>
    <version>1.1.2</version>
  </dependency>

10、jstl类型转换 int转String

<c:set var="teaid">
          <c:out value="${list.teaid }"/>
        </c:set>

11、servlet实现javascript

1、获取PrintWriter对象
PrintWriter out = response.getWriter();
2、实现js
// 警告框
out.write("<script type='text/javascript'>alert('警告框');</script>");
// 确认框
out.write("<script type='text/javascript'>confirm('确认弹框！');</script>");
// 重新加载页面
out.write("<script type='text/javascript'>location.reload();</script>");
// 放回当前页面
out.write("<script type='text/javascript'>history.go(-1);</script>");
3、关闭流
out.flush();
out.close();