如何在Tomcat 7中使用Servlet和JSP在MySQL数据库中插入图像

本文介绍了如何在Tomcat 7中使用Servlet和JSP在MySQL数据库中插入图像的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我试图在Tomcat 7中使用Servlet和JSP在MySQL数据库中插入图像.当我单击保存"按钮时，它显示为空.我没有任何错误.

I'm trying to insert an image in a MySQL database using Servlet and JSP in Tomcat 7. When I click on the save button, it displays null. I am not getting any errors.

我还设置了commons-fileupload.jar文件和commons-io.jar文件.如果您有一些演示代码，请给我.

Also I set commons-fileupload.jar file and commons-io.jar file. If you have some demonstration code, please give me.

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"pageEncoding="ISO-8859-1"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
      <title>File Upload to Database Demo</title>
    </head>
    <body>
      <center>
        <h1>File Upload to Database Demo</h1>
        <form method="post" action="FileUploadDBServlet" enctype="multipart/form-data">
        <table border="0">
            <tr>
                <td>First Name: </td>
                <td><input type="text" name="firstName" size="50"/></td>
            </tr>
            <tr>
                <td>Last Name: </td>
                <td><input type="text" name="lastName" size="50"/></td>
            </tr>
            <tr>
                <td>Portrait Photo: </td>
                <td><input type="file" name="photo" size="50"/></td>
            </tr>
            <tr>
                <td colspan="2">
                    <input type="submit" value="Save">
                </td>
            </tr>
        </table
      </form>
    </center>
  </body>
</html>

FileUploadDBServlet.java :

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;

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

    // database connection settings
    private String dbURL = "jdbc:mysql://localhost:3306/AppDB";
    private String dbUser = "root";
    private String dbPass = "root";

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        // gets values of text fields
        String firstName = request.getParameter("firstName");
        String lastName = request.getParameter("lastName");

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

        // obtains the upload file part in this multipart request
        Part filePart = request.getPart("photo");
        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 {

              Class.forName("com.mysql.jdbc.Driver").newInstance();
            conn = DriverManager.getConnection(dbURL,dbUser,dbPass);


            String sql =("INSERT INTO contacts (first_name, last_name, photo) values (?, ?, ?)");
            PreparedStatement statement = conn.prepareStatement(sql);
            statement.setString(1, firstName);
            statement.setString(2, lastName);

            if (inputStream != null) {
                // fetches input stream of the upload file for the blob column
                statement.setBlob(3, inputStream);
            }

            // sends the statement to the database server
            int row = statement.executeUpdate();
            if (row > 0) {
                message = "File uploaded and saved into database";
            }
        } catch (Exception  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);
        }
    }
}

web.xml :

<web-app>
  <servlet>
    <servlet-name>FileUploadDBServlet</servlet-name>
    <servlet-class>FileUploadDBServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>FileUploadDBServlet</servlet-name>
    <url-pattern>/FileUploadDBServlet</url-pattern>
  </servlet-mapping>
</web-app>

推荐答案

以下代码说明了如何在db中存储图像或从中获取图像.

The following code explains how to store/retrieve an image to/from db.

首先使用以下代码在数据库中创建一个表

First create a table in your db using following code

CREATE TABLE contacts (
    contact_id int PRIMARY KEY AUTO_INCREMENT,
    first_name varchar(45) DEFAULT NULL,
    last_name varchar(45) DEFAULT NULL,
    photo` mediumblob);

为输入参数创建一个jsp文件.

Create a jsp file for input parameters.

Upload.jsp:

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
                    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
        <title>File Upload to Database</title>
    </head>
    <body>
        <h1>File Upload to Database</h1>
        <form name="fileform" method="post" action="uploadServlet" enctype="multipart/form-data">
            <label for="firstName">First Name:</label>
            <input type="text" name="firstName" size="50" placeholder="Enter Your FirstName" required/><br><br>
            <label for="lastName">Last Name: </label>
            <input type="text" name="lastName" size="50" placeholder="Enter Your LastName" required/><br><br>
            <label for="photo"> Portrait Photo:  </label>
            <input type="file" name="photo" size="50" placeholder="Upload Your Image" required/><br><br>
            <input type="submit" value="Save">
        </form>
    </body>
</html>

接下来创建用于上传图片的控制器.在这种情况下，我使用的是servlet.

Next create controller for uploading image. In this case, I'm using a servlet.

FileUploadDbServlet.java:

package com.fileupload.attach;

import java.io.IOException;
import java.io.InputStream;
import java.io.FileOutputStream;
import java.io.OutputStream;
import java.sql.Blob;
import java.sql.ResultSet;
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.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;

@MultipartConfig(maxFileSize = 16177215)
// upload file's size up to 16MB
public class FileUploadDBServlet extends HttpServlet {
    private static final int BUFFER_SIZE = 4096;
    // database connection settings
    private String dbURL = "jdbc:mysql://localhost:3306/mysql";
    private String dbUser = "root";
    private String dbPass = "arun";

    //naive way to obtain a connection to database
    //this MUST be improved, shown for 
    private Connection getConnection() {
        Connection conn = null;
        try {
            DriverManager.registerDriver(new com.mysql.jdbc.Driver());
            conn = DriverManager.getConnection(dbURL, dbUser, dbPass);
        } catch (Exception e) {
            //wrapping any exception and rethrowing it
            //inside a RuntimeException
            //so the method is silent to exceptions
            throw new RuntimeException("Failed to obtain database connection.", e);
        }
        return conn;
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
        //get values of text fields
        String firstName = request.getParameter("firstName");
        String lastName = request.getParameter("lastName");
        InputStream inputStream = null; // input stream of the upload file
        // obtains the upload file part in this multipart request
        Part filePart = request.getPart("photo");
        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
            //the InputStream will point to a stream that contains
            //the contents of the 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
            conn = getConnection();
            // constructs SQL statement
            String sql = "INSERT INTO contacts (first_name, last_name, photo) values (?, ?, ?)";
            //Using a PreparedStatement to save the file
            PreparedStatement pstmtSave = conn.prepareStatement(sql);
            pstmtSave.setString(1, firstName);
            pstmtSave.setString(2, lastName);

            if (inputStream != null) {
                //files are treated as BLOB objects in database
                //here we're letting the JDBC driver
                //create a blob object based on the
                //input stream that contains the data of the file
                pstmtSave.setBlob(3, inputStream);
            }
            //sends the statement to the database server
            int row = pstmtSave.executeUpdate();
            if (row > 0) {
                message = "File uploaded and saved into database";
            }

            String filepath = "D:/Dev/JavaWorkSpaceNew/FileUploadDatabase/WebContent/FromDb.jpg";
            //Obtaining the file from database
            //Using a second statement
            String sql1 = "SELECT photo FROM contacts WHERE first_name=? AND last_name=?";
            PreparedStatement pstmtSelect = conn.prepareStatement(sql1);
            pstmtSelect.setString(1, firstName);
            pstmtSelect.setString(2, lastName);
            ResultSet result = pstmtSelect.executeQuery();
            if (result.next()) {
                Blob blob = result.getBlob("photo");
                InputStream inputStream1 = blob.getBinaryStream();
                OutputStream outputStream = new FileOutputStream(filepath);
                int bytesRead = -1;
                byte[] buffer = new byte[BUFFER_SIZE];
                while ((bytesRead = inputStream1.read(buffer)) != -1) {
                    outputStream.write(buffer, 0, bytesRead);
                }
                inputStream1.close();
                outputStream.close();
                System.out.println("File saved");
            }
        } catch (SQLException ex) {
            message = "ERROR: " + ex.getMessage();
            ex.printStackTrace();
        } finally {
            if (conn != null) {
                // closes the database connection
                try {
                    conn.close();
                } catch (SQLException ex) {
                    //silent
                }
            }
            // sets the message in request scope
            request.setAttribute("message", message);

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

web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app>
    <display-name>servletFileUpload</display-name>
    <welcome-file-list>
        <welcome-file>Upload.jsp</welcome-file>
    </welcome-file-list>
    <servlet>
        <description></description>
        <display-name>FileUploadDBServlet</display-name>
        <servlet-name>FileUploadDBServlet</servlet-name>
    <servlet-class>com.fileupload.attach.FileUploadDBServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>FileUploadDBServlet</servlet-name>
        <url-pattern>/uploadServlet</url-pattern>
    </servlet-mapping>
</web-app>

Message.jsp:

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
        pageEncoding="ISO-8859-1"%>
<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
        <title>Message</title>
    </head>
    <body>
        <h3>Result of the operation: ${message}</h3>
    </body>
</html>

这篇关于如何在Tomcat 7中使用Servlet和JSP在MySQL数据库中插入图像的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！