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我一直在研究一个 Java Servlet，它从用户在 index.html 中输入的表中选择所有数据。但是我遇到了一个问题，因为我有一个具有许多不同 ID 的数据库，因此我还想在表中显示列名 - 现在它只显示没有任何列名的数据而且我似乎无法寻找解决方案或自己想出一个解决方案
开始.java:
package start;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
import java.sql.SQLException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class Start
*/
@WebServlet("/Start")
public class Start extends HttpServlet {
private static final long serialVersionUID = 1L;
public static void getColumnNames(ResultSet rs) throws SQLException {
if (rs == null) {
return;
}
ResultSetMetaData rsMetaData = rs.getMetaData();
int numberOfColumns = rsMetaData.getColumnCount();
for (int i = 1; i < numberOfColumns + 1; i++) {
String columnName = rsMetaData.getColumnName(i);
String tableName = rsMetaData.getTableName(i);
System.out.println("column name=" + columnName + " table=" + tableName);
}
}
/**
* @see HttpServlet#HttpServlet()
*/
public Start() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
* response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse respond) throws ServletException, IOException {
PrintWriter pw = respond.getWriter();
respond.setContentType("text/html");
String tb = request.getParameter("table");
try {
Class.forName("com.mysql.jdbc.Driver").newInstance();
Connection con = DriverManager.getConnection("jdbc:mysql://localhost/music","root","1234");
Statement st = con.createStatement();
System.out.println("connection established successfully!");
ResultSet rs = st.executeQuery("SELECT * FROM " + tb);
pw.println("<table border=1>");
while (rs.next()) {
pw.println("<tr><td>" + rs.getInt(1) + "</td>" + "<td>" + rs.getString(2) + "</td>" + "<td>" + rs.getString(3)
+ "</td></tr>");
}
pw.println("</table>");
pw.close();
} catch (Exception e) {
e.printStackTrace();
}
// TODO Auto-generated method stub
// response.getWriter().append("Served at:
// ").append(request.getContextPath());
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
* response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
结果如下:
任何帮助将不胜感激!