连接数据库无非就是和数据库建立连接，和前面的python连接数据库差不多。
**首先在连接Java数据库的时候需要数据库的
jar
包，这点不同于python连接数据库**
mysql的jar包
下面让我们来看看数据库是如何让连接的，是如何完成数据库的一系列操作，增删改查等…
Java连接数据库。
1、注册驱动
Class.forName("com.mysql.jdbc.Driver");
2、获取连接
conn =DriverManager.getConnection("jdbc:mysql://localhost:3306/shop","root","123456");
注意：获取连接很重要，数据的一点点错误都会导致你连接不上数据库。
1、
localhost
代表本机不用变
2、
3306
是端口号，即port,一般默认都是3306。
3、
root
一般指管理员，不用变，直接用即可。
4、
"123456"
指的是密码，一般大家常用的密码就123、111111、root或者123456几种。
3、获取数据库操作对象
stmt = conn.createStatement();
4、//执行sql
String sql ="select id,name,num,price from testmodel_car";
rs = stmt.executeQuery(sql);while(rs.next()){String id = rs.getString("id");String name = rs.getString("name");String num = rs.getString("num");String price = rs.getString("price");System.out.println(id +","+ name +","+ num +","+ price);}}catch(Exception e){
e.printStackTrace();}finally{
**
注意：
**
😃1、
java"select id,name,num,price from testmodel_car";
，从表 testmodel_car中查询 id,name,num,price四列数据
😃2、
rs = stmt.executeQuery(sql);
，获取的对象编译一下sql语句
😃3、
String id = rs.getString("id");
，取出id那一列的值赋值给id(String id 中的id可以随便换，只要不和其他变量冲突都是可以的)
5、释放资源
if(rs !=null){try{
rs.close();}catch(Exception e){
e.printStackTrace();}}if(stmt !=null){try{
stmt.close();}catch(Exception e){
e.printStackTrace();}}if(conn !=null){try{
conn.close();}catch(Exception e){
e.printStackTrace();}}
不释放资源也行，在上面抛出异常也可以解决
6、完整代码
importcom.mysql.jdbc.Driver;importjava.sql.Connection;importjava.sql.DriverManager;importjava.sql.ResultSet;importjava.sql.Statement;publicclassTest2{publicstaticvoidmain(String[] args){Connection conn =null;Statement stmt =null;ResultSet rs =null;try{//注册驱动Class.forName("com.mysql.jdbc.Driver");//获取连接
conn =DriverManager.getConnection("jdbc:mysql://localhost:3306/shop","root","123456");//获取数据库操作对象
stmt = conn.createStatement();//执行sqlString sql ="select id,name,num,price from testmodel_car";
rs = stmt.executeQuery(sql);while(rs.next()){String id = rs.getString("id");String name = rs.getString("name");String num = rs.getString("num");String price = rs.getString("price");System.out.println(id +","+ name +","+ num +","+ price);}}catch(Exception e){
e.printStackTrace();}finally{//释放资源if(rs !=null){try{
rs.close();}catch(Exception e){
e.printStackTrace();}}if(stmt !=null){try{
stmt.close();}catch(Exception e){
e.printStackTrace();}}if(conn !=null){try{
conn.close();}catch(Exception e){
e.printStackTrace();}}}}}
连接数据库------增加操作
**
add.jsp
**
<%--
Created by IntelliJ IDEA.
User: 17331
Date: 2022/3/5
Time: 15:40
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<htmllang="en"><head><metacharset="UTF-8"><linkhref="h/favicon2.ico"rel="icon"type="image/x-icon"/><title>添加信息</title><style>body{background-color:#FDF5E6;}</style><style>body{width: 100%;height: 100%;background:url('./img/olypic.jpg');background-repeat: no-repeat;background-size: 100% 100%;background-attachment: fixed;}</style><style>input{width: 20%;padding: 12px 20px;margin: 8px 0;box-sizing: border-box;border: 1px solid #555;outline: none;}input:focus{background-color: lightblue;}</style><style>#boxshadow{position: relative;-moz-box-shadow: 1px 2px 4px rgba(0, 0, 0,0.5);-webkit-box-shadow: 1px 2px 4px rgba(0, 0, 0, .5);box-shadow: 1px 2px 4px rgba(0, 0, 0, .5);padding: 10px;background:#F0F8FF;border-radius:8px;}/* Make the image fit the box */#boxshadow img{width: 50%;border: 0px solid #8a4419;border-style: inset;}#boxshadow::after{content:'';position: absolute;z-index: -1;/* hide shadow behind image */-webkit-box-shadow: 0 15px 20px rgba(0, 0, 0, 0.3);-moz-box-shadow: 0 15px 20px rgba(0, 0, 0, 0.3);box-shadow: 0 15px 20px rgba(0, 0, 0, 0.3);width: 70%;left: 15%;/* one half of the remaining 30% */height: 100px;bottom: 0;}</style><style>.button{background-color:#337AB7;/* Green */border: none;color: white;padding: 16px 32px;text-align: center;text-decoration: none;display: inline-block;font-size: 16px;margin: 4px 2px;-webkit-transition-duration: 0.4s;/* Safari */transition-duration: 0.4s;cursor: pointer;}.button1{background-color: white;color: black;border: 2px solid #337AB7;}.button1:hover{background-color: #337AB7;color: white;box-shadow: 0 12px 16px 0 rgba(0,0,0,0.24),0 17px 50px 0 rgba(0,0,0,0.19);}</style></head><body><divstyle="padding:2px;width:1080px;height:470px;margin-top:10%;margin-left:20%;opacity: 0.8"id="boxshadow"><div><imgsrc="img/olypic.jpg"style="float:left;margin-top:5%;"></div><divstyle="float:right;"><formaction="add"method="post"><pstyle="margin-right:200px;">
国家名称   <inputtype="text"name="Country"style="border-radius:8px;width:150px;height:30px;"></p><p>
  金牌数     <inputtype="text"name="Glod_num"style="border-radius:8px;width:150px;height:30px;margin-top:1%"></p><p>
  银牌数     <inputtype="text"name="Silver_num"style="border-radius:8px;width:150px;height:30px;margin-top:1%"></p><p>
  铜牌数     <inputtype="text"name="Copper_num"style="border-radius:8px;width:150px;height:30px;margin-top:1%"></p><p>
     id           <inputtype="text"name="id"style="border-radius:8px;width:150px;height:30px;margin-top:1%"></p><inputtype="submit"value="保存"/><br/></form></form></div></div></body></html>
**
Add.java
**
packagecom.bjpowernode.javaweb.servlet;importcom.bjpowernode.javaweb.utils.DButil;importjavax.servlet.ServletException;importjavax.servlet.annotation.WebServlet;importjavax.servlet.http.HttpServlet;importjavax.servlet.http.HttpServletRequest;importjavax.servlet.http.HttpServletResponse;importjava.io.IOException;importjava.sql.*;@WebServlet(name ="add", value ="/add")publicclassAddextendsHttpServlet{@OverrideprotectedvoiddoPost(HttpServletRequest request,HttpServletResponse response)throwsServletException,IOException{
response.setContentType("text/html;charset=UTF-8");
request.setCharacterEncoding("UTF-8");//获取信息，前端页面注册的信息String country=request.getParameter("Country");// String logo=request.getParameter("logo");StringGlod_num=request.getParameter("Glod_num");StringSilver_num=request.getParameter("Silver_num");StringCopper_num=request.getParameter("Copper_num");String id =request.getParameter("id");// String Sum=request.getParameter("Sum");//连接数据库，执行insert插入语句Connection conn =null;PreparedStatement ps =null;int count=0;try{//注册驱动try{Class.forName("com.mysql.jdbc.Driver");}catch(ClassNotFoundException e){
e.printStackTrace();}//获取连接
conn =DriverManager.getConnection("jdbc:mysql://localhost:3306/mofa","root","123456");// TODO 2、开启事务 默认开启 我们将它关闭（）自动提交机制关闭String sql ="insert ignore into medals_table(Country,Glod_num,Silver_num,Copper_num,id) values (?,?,?,?,?);";
ps = conn.prepareStatement(sql);
ps.setString(1, country);// ps.setString(2, logo);
ps.setString(2,Glod_num);
ps.setString(3,Silver_num);
ps.setString(4,Copper_num);
ps.setString(5, id);// ps.setString(7, Sum);//返回一个值，指的是 影响了数据库中多少条记录 主要是判断是否大于0 就是是否印象数据库
count = ps.executeUpdate();}catch(SQLException e){
e.printStackTrace();}finally{DButil.close(conn,ps,null);}if(count==1){//增加成功 任然跳到列表页面
request.getRequestDispatcher("Take_01").forward(request,response);}else{//删除失败
request.getRequestDispatcher("error.jsp").forward(request,response);}}}
增加功能就是通过前端jsp文件text填写数据，然后通过submit提交数据，传递给后端servlet，也就是上面的Add，注意Java文件不要小写，我就没少挨骂
**
步骤：
**
😘1、前端jsp文件text写入通过submit提交
😘2、
<form action="add" method="post">
通过form表单提交给后端的servel(Add)
😘3、**
String country=request.getParameter("Country");
通过getParameter取到前端的值然后赋值给country，为后面刷数据做准备
😘4、后端servlet访问数据库，步骤访问上面第一个标题《Java连接数据库》**
😘5、成功将前端传来的数据刷如数据库
💖连接数据库------删除操作
packagecom.bjpowernode.javaweb.servlet;importcom.bjpowernode.javaweb.utils.DButil;importjavax.servlet.ServletException;importjavax.servlet.annotation.WebServlet;importjavax.servlet.http.HttpServlet;importjavax.servlet.http.HttpServletRequest;importjavax.servlet.http.HttpServletResponse;importjava.io.IOException;importjava.io.PrintWriter;importjava.sql.*;@WebServlet(name ="delete", value ="/delete")publicclassDeleteextendsHttpServlet{@OverrideprotectedvoiddoGet(HttpServletRequest request,HttpServletResponse response)throwsServletException,IOException{//根据部门编号删除部门//获取部门编号String country = request.getParameter("name");//连接数据库Connection conn =null;PreparedStatement ps =null;ResultSet rs =null;int count=0;try{//注册驱动Class.forName("com.mysql.jdbc.Driver");//获取连接
conn =DriverManager.getConnection("jdbc:mysql://localhost:3306/mofa","root","123456");// TODO 2、开启事务 默认开启 我们将它关闭（）自动提交机制关闭
conn.setAutoCommit(false);String sql ="delete from medals_table where Country=?";
ps = conn.prepareStatement(sql);
ps.setString(1,country);//返回一个值，指的是 影响了数据库中多少条记录 主要是判断是否大于0 就是是否印象数据库
count= ps.executeUpdate();//事务提交
conn.commit();}catch(SQLException e){if(conn!=null){try{
conn.rollback();}catch(SQLException ex){
ex.printStackTrace();}}
e.printStackTrace();}catch(ClassNotFoundException e){
e.printStackTrace();}finally{DButil.close(conn,ps,null);}if(count==1){PrintWriter out = response.getWriter();
out.println("<script>");
out.println("alert('Dear, the deletion is unrecoverable. Are you sure you deleted it？');");
out.println("location.href='Take_01'");//跳转到用户列表页面
out.println("</script>");// //删除成功 任然跳到列表页面// request.getRequestDispatcher("Take_01").forward(request,response);}else{//删除失败
request.getRequestDispatcher("error.jsp").forward(request,response);}}}
**
String country = request.getParameter("name");
，老规矩，前端取值进行操作**
💖连接数据库------修改操作
**
edit.jsp
**
<%--
Created by IntelliJ IDEA.
User: 17331
Date: 2022/3/6
Time: 17:39
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html><head><title><%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html><head><title>新增</title></head><body><h1>新增国家奖牌信息</h1><hrcolor="red"width="100%"><formaction="edit"method="post">
国家名称 :<inputtype='text'name='Country'value='"+country+"'/><br/>
<%-- logo :<inputtype='text'name='logo'value='"+logo+"'/><br/>--%>
金牌数 :<inputtype='text'name='Glod_num'value='"+Glod+"'/><br/>
银牌数 :<inputtype='text'name='Silver_num'value='"+Silver+"'/><br/>
铜牌数 :<inputtype='text'name='Copper_num'value='"+Copper+"'/><br/>
id : <inputtype='text'name='Sum'value='"+sum+"'/><br/>
总数 : <inputtype='text'name='id'value='"+id+"'/><br/><inputtype="submit"value="保存"/><br/></form></body></html>
**
Edit.java
**
packagecom.bjpowernode.javaweb.servlet;importcom.bjpowernode.javaweb.utils.DButil;importjavax.servlet.ServletException;importjavax.servlet.annotation.WebServlet;importjavax.servlet.http.HttpServlet;importjavax.servlet.http.HttpServletRequest;importjavax.servlet.http.HttpServletResponse;importjava.io.IOException;importjava.io.PrintWriter;importjava.sql.*;@WebServlet(name ="edit",value ="/edit")publicclassEditextendsHttpServlet{@OverrideprotectedvoiddoGet(HttpServletRequest request,HttpServletResponse response)throwsServletException,IOException{String contextPath = request.getContextPath();
response.setContentType("text/html;charset=UTF-8");
request.setCharacterEncoding("UTF-8");PrintWriter out =response.getWriter();//jsp文档
out.println("<html lang='en'>");
out.println("<head>");
out.println(" <meta charset='UTF-8'>");
out.println(" <link href='h/favicon2.ico' rel='icon' type='image/x-icon'/>");
out.println(" <title>添加信息</title>");
out.println(" <style>");
out.println(" body {");
out.println(" background-color:#FDF5E6;");
out.println(" }");
out.println(" </style>");
out.println(" <style>");
out.println(" body {");
out.println(" width: 100%;");
out.println(" height: 100%;");
out.println(" background: url('./img/olypic.jpg');");
out.println(" background-repeat: no-repeat;");
out.println(" background-size: 100% 100%;");
out.println(" background-attachment: fixed;");
out.println(" }");
out.println(" </style>");
out.println(" <style>");
out.println(" input{");
out.println(" width: 20%;");
out.println(" padding: 12px 20px;");
out.println(" margin: 8px 0;");
out.println(" box-sizing: border-box;");
out.println(" border: 1px solid #555;");
out.println(" outline: none;");
out.println(" }");
out.println("");
out.println(" input:focus {");
out.println(" background-color: lightblue;");
out.println(" }");
out.println(" </style>");
out.println(" <style>");
out.println(" #boxshadow {");
out.println(" position: relative;");
out.println(" -moz-box-shadow: 1px 2px 4px rgba(0, 0, 0,0.5);");
out.println(" -webkit-box-shadow: 1px 2px 4px rgba(0, 0, 0, .5);");
out.println(" box-shadow: 1px 2px 4px rgba(0, 0, 0, .5);");
out.println(" padding: 10px;");
out.println(" background:#F0F8FF;");
out.println(" border-radius:8px;");
out.println(" }");
out.println("");
out.println(" /* Make the image fit the box */");
out.println(" #boxshadow img {");
out.println(" width: 50%;");
out.println(" border: 0px solid #8a4419;");
out.println(" border-style: inset;");
out.println(" }");
out.println("");
out.println(" #boxshadow::after {");
out.println(" content: '';");
out.println(" position: absolute;");
out.println(" z-index: -1; /* hide shadow behind image */");
out.println(" -webkit-box-shadow: 0 15px 20px rgba(0, 0, 0, 0.3);");
out.println(" -moz-box-shadow: 0 15px 20px rgba(0, 0, 0, 0.3);");
out.println(" box-shadow: 0 15px 20px rgba(0, 0, 0, 0.3);");
out.println(" width: 70%;");
out.println(" left: 15%; /* one half of the remaining 30% */");
out.println(" height: 100px;");
out.println(" bottom: 0;");
out.println(" }");
out.println(" </style>");
out.println(" <style>");
out.println(" .button {");
out.println(" background-color:#337AB7; /* Green */");
out.println(" border: none;");
out.println(" color: white;");
out.println(" padding: 16px 32px;");
out.println(" text-align: center;");
out.println(" text-decoration: none;");
out.println(" display: inline-block;");
out.println(" font-size: 16px;");
out.println(" margin: 4px 2px;");
out.println(" -webkit-transition-duration: 0.4s; /* Safari */");
out.println(" transition-duration: 0.4s;");
out.println(" cursor: pointer;");
out.println(" }");
out.println("");
out.println(" .button1 {");
out.println(" background-color: white;");
out.println(" color: black;");
out.println(" border: 2px solid #337AB7;");
out.println(" }");
out.println(" .button1:hover {");
out.println(" background-color: #337AB7;");
out.println(" color: white;");
out.println(" box-shadow: 0 12px 16px 0 rgba(0,0,0,0.24),0 17px 50px 0 rgba(0,0,0,0.19);");
out.println(" }");
out.println(" </style>");
out.println("");
out.println("</head>");
out.println("<body>");
out.println("");
out.println("<div style='padding:2px;width:1080px;height:470px;margin-top:10%;margin-left:20%;opacity: 0.8' id='boxshadow'>");
out.println(" <div>");
out.println(" <img src='img/olypic.jpg' style='float:left;margin-top:5%;'>");
out.println(" </div>");
out.println(" <div style='float:right;'>");
out.println(" <form action='"+contextPath+"/update' method='post'>");//获取国家名称String country=request.getParameter("name");//连接数据库Connection conn=null;PreparedStatement ps=null;ResultSet rs=null;try{try{Class.forName("com.mysql.jdbc.Driver");}catch(ClassNotFoundException e){
e.printStackTrace();}//获取连接
conn =DriverManager.getConnection("jdbc:mysql://localhost:3306/mofa","root","123456");String sql ="select * from medals_table where Country=?";//编译sql语句
ps = conn.prepareStatement(sql);//赋值 第一个问好赋值 country 国家名称
ps.setString(1, country);//查询返回结果集 这个结果集只有一条记录 ，国家名称是主键 ， 故只有一条数据
rs = ps.executeQuery();if(rs.next()){String logo=rs.getString("logo");StringGlod= rs.getString("Glod_num");StringSilver= rs.getString("Silver_num");StringCopper= rs.getString("Copper_num");String sum=rs.getString("Sum");String id=rs.getString("id");System.out.println("你好，你好，你好，齐天大圣！！！");//输出动态网页
out.println("<p style='margin-right:200px;'>");
out.println(" 国家名称   <input type='text' name='Country' value='"+country+"' style='border-radius:8px;width:150px;height:30px;'>");
out.println(" </p>");// out.println(" <p>");// out.println("    logo      <input type='text' name='logo' value='"+logo+"' style='border-radius:8px;width:150px;height:30px;margin-top:1%'>");// out.println(" </p>");
out.println(" <p>");
out.println("   金牌数     <input type='text' name='Glod_num' value='"+Glod+"' style='border-radius:8px;width:150px;height:30px;margin-top:1%'>");
out.println(" </p>");
out.println("");
out.println(" <p>");
out.println("   银牌数     <input type='text' name='Silver_num' value='"+Silver+"' style='border-radius:8px;width:150px;height:30px;margin-top:1%'>");
out.println(" </p>");
out.println(" <p>");
out.println("   铜牌数     <input type='text' name='Copper_num' value='"+Copper+"' style='border-radius:8px;width:150px;height:30px;margin-top:1%'>");
out.println(" </p>");
out.println(" <p>");
out.println("      id           <input type='text' name='id' value='"+id+"' style='border-radius:8px;width:150px;height:30px;margin-top:1%'>");
out.println(" </p>");}}catch(SQLException e){
e.printStackTrace();}finally{DButil.close(conn,ps,rs);}
out.println(" <input type='submit' value='保存'/><br/>");
out.println(" </form>");
out.println(" </form>");
out.println(" </div>");
out.println("</div>");
out.println("</body>");
out.println("</html>");}}
**
Update.java
**
packagecom.bjpowernode.javaweb.servlet;importcom.bjpowernode.javaweb.utils.DButil;importjavax.servlet.ServletException;importjavax.servlet.annotation.WebServlet;importjavax.servlet.http.HttpServlet;importjavax.servlet.http.HttpServletRequest;importjavax.servlet.http.HttpServletResponse;importjava.io.IOException;importjava.sql.*;@WebServlet(name ="update",value ="/update")publicclassUpdateextendsHttpServlet{@OverrideprotectedvoiddoPost(HttpServletRequest request,HttpServletResponse response)throwsServletException,IOException{
response.setContentType("text/html;charset=UTF-8");
request.setCharacterEncoding("UTF-8");//解决中文乱码问题String country=request.getParameter("Country");String logo=request.getParameter("logo");StringGlod_num=request.getParameter("Glod_num");StringSilver_num=request.getParameter("Silver_num");StringCopper_num=request.getParameter("Copper_num");String id=request.getParameter("id");//连接数据库执行更新操作Connection conn =null;PreparedStatement ps =null;ResultSet rs =null;int count=0;try{try{Class.forName("com.mysql.jdbc.Driver");}catch(ClassNotFoundException e){
e.printStackTrace();}//获取连接
conn =DriverManager.getConnection("jdbc:mysql://localhost:3306/mofa","root","123456");String sql ="update medals_table set Glod_num=?,Silver_num=?,Copper_num=?,id=? where Country=?";//编译sql语句
ps = conn.prepareStatement(sql);// ps.setString(1, logo);
ps.setString(1,Glod_num);
ps.setString(2,Silver_num);
ps.setString(3,Copper_num);
ps.setString(4, id);
ps.setString(5, country);// System.out.println(logo);
count=ps.executeUpdate();System.out.println(count);}catch(SQLException e){
e.printStackTrace();}finally{DButil.close(conn, ps, rs);}if(count==1){//更新成功
request.getRequestDispatcher("Take_01").forward(request,response);}else{//更新失败
request.getRequestDispatcher("error.jsp").forward(request,response);}}}**```
前端传输数据给后端edit,edit通过getParameter取到前端值完成后面的操作。**
为了让修改的时候可以显示修改前的值，我们在Edit.java中写入前端代码。**Edit.jav中代码通过form表单把数据传输给Update.java。**Update.java通过getParameter取到由Edit.java中传来的值。**
把取到的值存进数据库，完成刷入操作。******`注意：我这里有个bug，就是不能修改国家名称，因为手贱的我为了让数据库看着好看就把国家名设置为主键了，，，，，，，`********
连接数据库------查询操作
**`Select.java`**
```java
packagecom.bjpowernode.javaweb.servlet;importcom.bipowernode.pojo.Olypic;importcom.bjpowernode.javaweb.utils.DButil;importjavax.servlet.ServletException;importjavax.servlet.annotation.WebServlet;importjavax.servlet.http.HttpServlet;importjavax.servlet.http.HttpServletRequest;importjavax.servlet.http.HttpServletResponse;importjava.io.IOException;importjava.io.PrintWriter;importjava.sql.*;importjava.util.ArrayList;importjava.util.List;@WebServlet(name ="select",value ="/select")publicclassSelectextendsHttpServlet{@OverrideprotectedvoiddoPost(HttpServletRequest request,HttpServletResponse response)throwsServletException,IOException{
response.setContentType("text/html;charset=UTF-8");
request.setCharacterEncoding("UTF-8");String name = request.getParameter("select_name");System.out.println(name);//连接数据库Connection conn =null;PreparedStatement ps =null;ResultSet rs =null;List<Olypic> olypicList=newArrayList<>();try{Class.forName("com.mysql.jdbc.Driver");//获取连接
conn =DriverManager.getConnection("jdbc:mysql://localhost:3306/mofa","root","123456");String sql ="select * from medals_table where Country=?";//编译sql语句
ps = conn.prepareStatement(sql);//赋值 第一个问好赋值 country 国家名称
ps.setString(1, name);//查询返回结果集 这个结果集只有一条记录 ，国家名称是主键 ， 故只有一条数据
rs = ps.executeQuery();if(rs.next()){String country = rs.getString("Country");StringGlod= rs.getString("Glod_num");StringSilver= rs.getString("Silver_num");StringCopper= rs.getString("Copper_num");String id=rs.getString("id");String logo=rs.getString("logo");System.out.println("这是数据");System.out.println(country);System.out.println("Glod");// String Sum=rs.getString("Sum");intG=Integer.valueOf(Glod).intValue();intS=Integer.valueOf(Silver).intValue();intC=Integer.valueOf(Copper).intValue();intA=G+S+C;StringSum=String.valueOf(A);//将数据封装程Java对象Olypic olpic=newOlypic();
olpic.setCountry(country);
olpic.setGlod_num(Glod);
olpic.setSilver_num(Silver);
olpic.setCopper_num(Copper);
olpic.setId(id);
olpic.setSum(Sum);
olpic.setLogo(logo);// TODO 将数据放入上面定义好的容器
olypicList.add(olpic);}}catch(SQLException e){
e.printStackTrace();}catch(ClassNotFoundException e){
e.printStackTrace();}finally{DButil.close(conn, ps, rs);}
request.setAttribute("olypicList",olypicList);
request.getRequestDispatcher("./take_03.jsp").forward(request,response);}}
可以从前端或者后端传值，完成搜索操作。但是一般是要通过前端搜索框输入值，通过form表单传走，后端通过getParameter取值完成一些列操作。
现在的项目都是通过框架，但是 了解传输和运行机制还是十分重要的。
完整的JavaWeb项目
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本文转载自: https://blog.csdn.net/m0_69481606/article/details/124361776
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版权归原作者 凉薄少年不良 所有， 如有侵权，请联系我们删除。