Question

所以我正在编写一个简单处理我的表单的servlet。表单实际上是一个注册页面，只有附加的文件输入。因此，我需要将其作为multipart和method post。 servlet使用doPost方法来检索信息。另一方面，servlet还从其他包中的另一个类检索信息。该类是读取属性文件。我已经完成了我的研究，浏览互联网以及官方页面上的文档。任何人都可以帮助我吗？

servlet代码

package net.codejava.upload;


import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;

import readConfig.readConfig;

@WebServlet("/uploadServlet")
@MultipartConfig(maxFileSize = 16177215)    // upload file's size up to   16MB
public class FileUploadDBServlet extends HttpServlet {

/**
 * 
 */
private static final long serialVersionUID = 1L;

/**
 * 
 */



    readConfig readcfg= new readConfig();

// database connection setting

String dbURL = readcfg.getProperties("conUrl");
String dbUser = readConfig.getProperties("dbUser");
String dbPass = readConfig.getProperties("dbUser");


protected void doPost(HttpServletRequest request,
        HttpServletResponse response) throws ServletException, IOException {
    // gets values of text fields
    String name = request.getParameter("name");
    String address = request.getParameter("address");
    String city = request.getParameter("city");
    String email = request.getParameter("email");
    String password = request.getParameter("password");

    System.out.println(dbURL);
    System.out.println(dbUser);
    System.out.println(dbPass);

    InputStream inputStream = null; // input stream of the upload file

    // obtains the upload file part in this multipart request
    Part filePart = request.getPart("file");
    if (filePart != null) {
        // prints out some information for debugging
        System.out.println(filePart.getName());
        System.out.println(filePart.getSize());
        System.out.println(filePart.getContentType());

        // obtains input stream of the upload file
        inputStream = filePart.getInputStream();
    }

    Connection conn = null; // connection to the database
    String message = null;  // message will be sent back to client

    try {
        // connects to the database
        DriverManager.registerDriver(new com.mysql.jdbc.Driver());
        conn = DriverManager.getConnection(dbURL, dbUser, dbPass);

        // constructs SQL statement
        String sql = "INSERT INTO ssl_user (name, address, password,city,email,file) values (?, ?, ?, ?, ?, ?)";
        PreparedStatement statement = conn.prepareStatement(sql);
        statement.setString(1, name);
        statement.setString(2, address);
        statement.setString(3, password);
        statement.setString(4, city);
        statement.setString(5, email);

        if (inputStream != null) {
            // fetches input stream of the upload file for the blob column
            statement.setBlob(6, inputStream);
        }

        // sends the statement to the database server
        int row = statement.executeUpdate();
        if (row > 0) {
            message = "File uploaded and saved into database";
        }
    } catch (SQLException ex) {
        message = "ERROR: " + ex.getMessage();
        ex.printStackTrace();
    } finally {
        if (conn != null) {
            // closes the database connection
            try {
                conn.close();
            } catch (SQLException ex) {
                ex.printStackTrace();
            }
        }
        // sets the message in request scope
        request.setAttribute("Message", message);

        // forwards to the message page
        getServletContext().getRequestDispatcher("/Message.jsp").forward(request, response);
    }
}

}

读取属性的类

package readConfig;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;
public class readConfig {
//call this method from jsp
public static String getProperties(String key) throws IOException
{
InputStream inputStream=readConfig.class.getClassLoader().getResourceAsStream("config.properties");
Properties myproperties = new Properties();
/////////////load the properties file
myproperties.load(inputStream);

return myproperties.getProperty(key);
}
}

Answer 1

您应该在错误日志中分享您所获得的内容，以便我们可以更好地帮助您。我可以假设您在尝试连接到数据库时必须获得NullPointerException。 1＆gt;在config.properties文件中，您应该为键设置值，如下所示（这只是一个示例）

dbURL=jdbc:mysql://localhost:3306/mydb 
dbUser=root
dbPass=root

2＆gt;在你的Servlet类中，我假设你在变量dbPass中设置了错误的值

从

更改

String dbPass = readConfig.getProperties("dbUser");

到

String dbPass = readConfig.getProperties("dbPass");

您在密码变量中设置用户名

3＆gt;这只是一个建议类的名称应以大写字母开头（在您的代码类readConfig中）

Answer 2

所以我想出了我的代码的错误。由于getProperties类是实现IOException，因此默认构造函数无法读取它。因此，解决方案只是移动doPost类中的数据库连接设置。哈哈，谢谢。

如何使用doPost从另一个类获取变量

2 个答案: