2021-10-23

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以下代码存在一个问题，就是后端代码无法获取html中的输入框值，可能跟web.xml有关。

package Servlet;

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.IOException;
import java.io.PrintWriter;
import java.sql.*;
import java.util.ArrayList;

@WebServlet(name = “WelcomeServlet”,urlPatterns={"/Servlet"})
public class WelcomeServlet extends HttpServlet {
ArrayList bookList = new ArrayList();
Connection dbconn = null;
ResultSet result = null;
PreparedStatement pstmt = null;
public void init() {
String url = “jdbc:mysql://localhost:3306/db_cms?useSSL=false”;
String username =“root”;
String password = “ronghui123@”;
try{
Class.forName(“com.mysql.jdbc.Driver”);
dbconn = DriverManager.getConnection(url,username,password);
System.out.println(“数据库连接成功!”);
}catch (ClassNotFoundException e1){
System.out.println(e1+“驱动程序找不到”);
}catch(SQLException e2){
System.out.println(e2);
}
}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
	//界面布局
	response.setContentType("text/html;charset=UTF-8");
	response.setHeader("content-type","text/html;charset=utf-8");
	PrintWriter out = response.getWriter();
	out.print("
");
	out.print("
");
	out.print("输入您要查询的书籍信息
");
	out.print("

");
	out.print("");
	out.print("");
	out.print("");
	out.print("");
	out.print("");
	out.print("

");
	out.print("
");
	out.print("
");
	out.print("
");
	//返回符合条件的商品
    try{
        String sql = "select * from T_BOOK where bookname like CONCAt('%','史','%')";//查询语句决定了是否是模糊查询
        pstmt = dbconn.prepareStatement(sql);
        result = pstmt.executeQuery();
        while(result.next()){
            Book product = new Book();
            product.setBookid(result.getInt("bookid"));
            product.setBookname(result.getString("bookname"));
            product.setBookprice(result.getFloat("bookprice"));
            bookList.add(product);
        }
        if(bookList==null){
            System.out.print("数据库列表为空！");
        }
    }catch (SQLException e){
        e.printStackTrace();
    }
    //遍历输出查找到的符合条件的商品
	for (int i=0;i");
    }
}
public void destroy(){
    try{
        dbconn.close();
    }catch(Exception e){
        e.printStackTrace();
    }
}

}