servlet查询MySQL

最新推荐文章于 2021-01-30 08:19:13 发布

转载最新推荐文章于 2021-01-30 08:19:13 发布 · 745 阅读

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本文详细解析了一个使用Java Servlet实现图书查询功能的案例。通过创建数据库连接、执行SQL查询并处理结果，该示例展示了如何从图书数据库中获取指定作者的图书信息，并以HTML页面形式呈现查询结果。

// Saved as "ebookshop\WEB-INF\classes\QueryServlet.java".
import java.io.*;
import java.sql.*;
import javax.servlet.*;
import javax.servlet.http.*;
 
public class QueryServlet extends HttpServlet {  // JDK 6 and above only
 
   // The doGet() runs once per HTTP GET request to this servlet.
   @Override
   public void doGet(HttpServletRequest request, HttpServletResponse response)
                     throws ServletException, IOException {
      // Set the MIME type for the response message
      response.setContentType("text/html");
      // Get a output writer to write the response message into the network socket
      PrintWriter out = response.getWriter();
 
      Connection conn = null;
      Statement stmt = null;
      try {
         // Step 1: Create a database "Connection" object
         // For MySQL
    	  Class.forName("com.mysql.jdbc.Driver").newInstance();//原文少了这一句
         conn = DriverManager.getConnection(
            "jdbc:mysql://localhost/ebookshop", "root", "");  // <<== Check
         // For MS Access
         // conn = DriverManager.getConnection("jdbc:odbc:ebookshopODBC");
 
         // Step 2: Create a "Statement" object inside the "Connection"
         stmt = conn.createStatement();
 
         // Step 3: Execute a SQL SELECT query
         String sqlStr = "SELECT * FROM books WHERE author = "
               + "'" + request.getParameter("author") + "'"
               + " AND qty > 0 ORDER BY author ASC, title ASC";
 
         // Print an HTML page as output of query
         out.println("<html><head><title>Query Results</title></head><body>");
         out.println("<h2>Thank you for your query.</h2>");
         out.println("<p>You query is: " + sqlStr + "</p>"); // Echo for debugging
         ResultSet rset = stmt.executeQuery(sqlStr); // Send the query to the server
 
         // Step 4: Process the query result
         int count = 0;
         while(rset.next()) {
            // Print a paragraph <p>...</p> for each row
            out.println("<p>" + rset.getString("author")
                  + ", " + rset.getString("title")
                  + ", $" + rset.getDouble("price") + "</p>");
            ++count;
         }
         out.println("<p>==== " + count + " records found ====</p>");
         out.println("</body></html>");
      } catch (SQLException | InstantiationException | IllegalAccessException | ClassNotFoundException ex) {
         ex.printStackTrace();
      } finally {
         out.close();
         try {
            // Step 5: Close the Statement and Connection
            if (stmt != null) stmt.close();
            if (conn != null) conn.close();
         } catch (SQLException ex) {
            ex.printStackTrace();
         }
      }
   }
}

原文：http://www.ntu.edu.sg/home/ehchua/programming/java/JavaServletCaseStudy.html

源代码：http://pan.baidu.com/share/link?shareid=16310733&uk=3878681452