我正在关注http://www.codejava.net/coding/upload-files-to-database-servlet-jsp-mysql中的代码。我修改了一些代码，现在正在运行。我现在的问题是，我还添加了“select * from contact”来查看上传文件的值，但是其字段中存储的值是二进制格式（数据库中的数据类型是varbinary）
是否可以将二进制数据转换为String，这样当它存储在数据库中时，该值已经是String格式？当我执行“select * from contact”时，显示的字段的值将采用String格式？
FileUploadDB.java
package com.process.web.controller;
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("/fileuploaddb.html")
@MultipartConfig(maxFileSize = 16177215)
public class FileUploadDB extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request,response);
}
private String dbURL = "jdbc:jtds:sqlserver://localhost:1433;DatabaseName=ATS;SelectMethod=cursor;";
private String dbUser = "sa";
private String dbPass = "benilde";
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 {
// connects to the database
//DriverManager.registerDriver(new com.mysql.jdbc.Driver());
//DriverManager.getConnection(dbURL);
//com.microsoft.sqlserver.jdbc.Driver
Class.forName("net.sourceforge.jtds.jdbc.Driver").newInstance();
conn = DriverManager.getConnection(dbURL, dbUser, dbPass);
if(conn!=null) {
System.out.println("Connection Successful!");
} else {
System.out.println("Error in Connection");
}
// constructs SQL statement
String sql = "INSERT INTO contact (firstname, lastname, 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.setBinaryStream(3, filePart.getInputStream(), (int)(filePart.getSize()));
}
// 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();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InstantiationException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.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);
}
}
}
这是upload.jsp
<%@ 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="fileuploaddb.html" 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>
**This is the Message.jsp**
<%@ 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>Message</title>
</head>
<body>
<center>
<h3><%=request.getAttribute("Message")%></h3>
</center>
</body>
</html>
答案 0 :(得分：1)
AbstractMethodError意味着你的JDBC驱动程序的PreparedStatements没有实现
setBlob(int, InputStream).
刚刚看到你正在使用的驱动程序，并且根据它没有采取的文档
`setBlob(int, InputStream)`
但需要
setBlob(int parameterIndex, java.sql.Blob x)
请阅读此文档http://jtds.sourceforge.net/doc/net/sourceforge/jtds/jdbc/JtdsPreparedStatement.html以获取进一步的帮助，否则我建议您更改正在使用的驱动程序。
请参阅此SO post