运行 post 方法后，我无法将输出字符串打印到 .jsp 文件中。下面是我的 .java 和 .jsp 文件。我已经删除了那里的代码，因为此时我知道我所尝试的内容远非直观。我只是在我知道需要分别处理两行代码的地方留下了注释。我只是想在 servlet 执行 SQL 命令后在 .jsp 文件中打印字符串“out”。
编辑: 我终于将所有输出发送到 JSP 页面。我现在遇到的唯一问题是，我将查询结果存储在输出字符串中的不太理想的方法导致我的输出是一长行结果，而不是一个很好的间距或表格。我知道我最好循环遍历 jsp 中表格中的结果，但我似乎也无法让它工作。
dbServlet.jsp
<?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">
<head>
<title>MySQL Servlet</title>
<style type="text/css">
body{background-color: green;}
</style>
</head>
<body>
<h1>Hello World!</h1>
<h2>This is the MySQL Servlet</h2>
<form action = "/database/database" method = "post">
<p>
<label>Enter your query and click the button to invoke a MySQL Servlet
<input type = "text" name = "query" />
<input type = "submit" value = "Run MySQL Servlet" />
</label>
</p>
</form>
<hr>
<%= request.getAttribute("queryResults") %>
</body>
</html>
数据库Servlet.java
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.sql.*;
@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 {
String out = "\n";
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++){
out = out + "\t" + metaData.getColumnName(i) + "\n";
}
out = out + "\n";
while (resultSet.next()){
for (int i = 1; i <= numberOfColumns; i++){
out = out + "\t" + resultSet.getObject(i) + "\n";
}
out = out + "\n";
}
}
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());
out = "\t\t Database has been updated!";
}
catch (Exception l){
l.printStackTrace();
}
}
else {
//Not a valid response
out = "\t\t Not a valid command or query!";
}
request.setAttribute("queryResults", out);
RequestDispatcher dispatcher = request.getRequestDispatcher("/dbServlet.jsp");
dispatcher.forward(request, response);
}
}
最佳答案
您不能只执行 out.println 并在 JSP 上打印。您需要将其放入响应对象中并转发到 JSP。然后 JSP 可以获取并打印它。
关于java - 将字符串从 servlet 传递到 .jsp，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/13408115/