以下java代碼接受來自JSP文件的POST請求,並將返回的ArrayList作爲輸出返回。我遇到的問題是弄清楚如何正確地將輸出讀入Arraylist,以便他們可以從Arraylist中獲取每個元素並將其顯示在我的JSP中。使用Java將MySQL查詢結果存儲在ArrayList中
如何讀取列名作爲第一個字符串數組,然後將每行數據作爲以下字符串數組,以便我有一個巨大的數組列表,其中包含查詢的全部結果有組織的方式,並允許我將結果讀到我的JSP頁面上?
編輯: 所以我現在具有唯一的問題是執行像SELECT * FROM表的指令時;它只顯示列名。但是當我執行像SELECT columnName FROM table這樣的命令時;它完美地顯示列。下面的代碼已經更新,以反映我現在的位置。
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.sql.*;
import java.util.ArrayList;
@SuppressWarnings("serial")
public class databaseServlet extends HttpServlet {
private Connection conn;
private Statement statement;
public void init(ServletConfig config) throws ServletException {
try {
Class.forName(config.getInitParameter("databaseDriver"));
conn = DriverManager.getConnection(
config.getInitParameter("databaseName"),
config.getInitParameter("username"),
config.getInitParameter("password"));
statement = conn.createStatement();
}
catch (Exception e) {
e.printStackTrace();
}
}
protected void doPost (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
ArrayList<String[]> out = new ArrayList<String[]>();
ArrayList<String> columns = new ArrayList<String>();
String query = request.getParameter("query");
if (query.toString().toLowerCase().contains("select")) {
//SELECT Queries
//try {
ResultSet resultSet = statement.executeQuery(query.toString());
ResultSetMetaData metaData = resultSet.getMetaData();
int numberOfColumns = metaData.getColumnCount();
for(int i = 1; i<= numberOfColumns; i++){
columns.add(metaData.getColumnName(i));
}
while (resultSet.next()){
String[] row = new String[numberOfColumns];
for (int i = 0; i < numberOfColumns; i++){
row[i] = (String) resultSet.getObject(i+1);
}
out.add(row);
}
//}
//catch (Exception f) {
//f.printStackTrace();
//}
}
else if (query.toString().toLowerCase().contains("delete") || query.toLowerCase().contains("insert")) {
//DELETE and INSERT commands
//try {
conn.prepareStatement(query.toString()).executeUpdate(query.toString());
columns.add("\t\t Database has been updated!");
//}
//catch (Exception l){
//l.printStackTrace();
//}
}
else {
//Not a valid response
columns.add("\t\t Not a valid command or query!");
}
request.setAttribute("query", query);
request.setAttribute("resultSize", out.size());
request.setAttribute("queryResults", out);
request.setAttribute("queryColumns", columns);
RequestDispatcher dispatcher = request.getRequestDispatcher("/dbServlet.jsp");
dispatcher.forward(request, response);
}
}
這裏是我的.jsp文件,而現在它與什麼也沒有,當我執行命令只能打印[]。我知道由於之前的測試命令正在工作,但數組顯示不正確。
<?xml version = "1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<!-- dbServlet.html -->
<html xmlns = "http://www.w3.org/1999/xhtml">
<%@ page import="java.util.ArrayList" %>
<head>
<title>MySQL Servlet</title>
<style type="text/css">
body{background-color: green;}
</style>
</head>
<body>
<h1>This is the MySQL Servlet</h1>
<form action = "/database/database" method = "post">
<p>
<label>Enter your query and click the button to invoke a MySQL Servlet
<textarea name = "query" cols="20" rows="5"></textarea>
<input type = "submit" value = "Run MySQL Servlet" />
<input type = "reset" value = "Clear Command" />
</label>
</p>
</form>
<hr>
<TABLE id="results">
<%
ArrayList<String> columns = (ArrayList<String>)request.getAttribute("queryColumns");
ArrayList<String[]> results = (ArrayList<String[]>)request.getAttribute("queryResults");
out.println("<TR>");
if(columns != null && !columns.isEmpty()){
for(String columnName: columns){
out.println("<TD>"+columnName+"</TD>");
}
}
out.println("</TR>");
//print data
if(results != null && !results.isEmpty()){
for(String[] rowData: results){
out.println("<TR>");
for(String data: rowData){
out.println("<TD>"+data+"</TD>");
}
out.println("</TR>");
}
}
%>
</TABLE>
<%= request.getAttribute("query") %>
<%= request.getAttribute("resultSize") %>
</body>
</html>
@Animachine:在您的JSP中使用這兩個屬性,正如我在上一個問題中所建議的那樣。 –
當我嘗試在ym JSP中使用這兩個屬性時,出現錯誤,而當我僅使用queryResults時,我得到的唯一輸出是空括號「[]」。 我用我當前的代碼更新了我的問題,包括.java和.jsp – PeerPressure
@Animachine:您沒有像我在[** this answer **]中所建議的那樣使用JSP(http://stackoverflow.com/questions/13410284 /顯示MySQL的查詢 - 結果 - 從 - 的servlet到JSP/13410331#13410331)。請參閱。 –