【发布时间】：2015-08-11 14:31:13
【问题描述】：
我正在使用 Servlet 从我的数据库中加载 PDF 文件并将其显示在页面上的 HTML <object> 上。
我的页面包含一个下载按钮，该按钮将参数传递给 servlet 并从我的数据库下载另一个文件。我的 PDF Servlet 工作正常，但没有从我的 JSP 页面获取参数以在页面上加载文件。
例如：我的 PDF Servlet 上有一个SELECT 查询以获取正确的 PDF 文件： select pdf from pdf where id = ?，问题是servlet 无法从页面中获取参数并将其放入我的? 查询中。但是，如果我像select pdf from pdf where id = 1 那样手动操作，那么我的页面会加载 PDF 文件。
这是我的 index.jsp：
<%--
Document : index
Created on : 06/08/2015, 16:14:51
Author : Henrique
--%>
<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>JSP Page</title>
</head>
<body>
<h1>Teste Download XML</h1>
<form action="${pageContext.request.contextPath}/downloadDB">
<input type="hidden" name="id" value="<%=request.getParameter("id")%>" />
<button type="submit">Download</button>
</form>
<object data="pdf" type="application/pdf" width="1000" height="1000"/>
</body>
</html>
这是我的 DisplayPDF Servlet doGet 方法：
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
int uploadId = Integer.parseInt(request.getParameter("id"));
Connection conn = null; // connection to the database
try {
// connects to the database
DriverManager.registerDriver(new com.mysql.jdbc.Driver());
conn = DriverManager.getConnection(dbURL, dbUser, dbPass);
// queries the database
String sql = "SELECT * FROM xmlNFe WHERE xml_id = ?";
PreparedStatement statement = conn.prepareStatement(sql);
statement.setInt(1, uploadId);
ResultSet result = statement.executeQuery();
if (result.next()) {
Blob blob = result.getBlob("xml_pdf");
InputStream inputStream = blob.getBinaryStream();
String fileName = result.getString("xml_chnfe");
int fileLength = inputStream.available();
System.out.println("fileLength = " + fileLength);
ServletContext context = getServletContext();
// sets MIME type for the file download
String mimeType = context.getMimeType(fileName);
if (mimeType == null) {
mimeType = "application/pdf";
}
response.setContentType(mimeType);
response.setContentLength(fileLength);
String headerKey = "Content-Disposition";
String headerValue = String.format("Content-Disposition", "inline; filename=\"" + fileName + "\"");
response.setHeader(headerKey, headerValue);
OutputStream outputStream = response.getOutputStream();
byte[] buffer = new byte[BUFFER_SIZE];
int bytesRead = -1;
while ((bytesRead = inputStream.read(buffer)) != -1) {
outputStream.write(buffer, 0, bytesRead);
}
inputStream.close();
outputStream.close();
}
} catch (SQLException ex) {
Logger.getLogger(DisplayPDF.class.getName()).log(Level.SEVERE, null, ex);
}
}
这是我在用户单击“下载”按钮时调用的另一个 servlet：
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// get upload id from URL's parameters
int uploadId = Integer.parseInt(request.getParameter("id"));
Connection conn = null; // connection to the database
try {
// connects to the database
DriverManager.registerDriver(new com.mysql.jdbc.Driver());
conn = DriverManager.getConnection(dbURL, dbUser, dbPass);
// queries the database
String sql = "SELECT * FROM xmlNFe WHERE xml_id = ?";
PreparedStatement statement = conn.prepareStatement(sql);
statement.setInt(1, uploadId);
ResultSet result = statement.executeQuery();
if (result.next()) {
// gets file name and file blob data
String fileName = result.getString("xml_chnfe");
Blob blob = result.getBlob("xml_xml");
InputStream inputStream = blob.getBinaryStream();
int fileLength = inputStream.available();
System.out.println("fileLength = " + fileLength);
ServletContext context = getServletContext();
// sets MIME type for the file download
String mimeType = context.getMimeType(fileName);
if (mimeType == null) {
mimeType = "application/octet-stream";
}
// set content properties and header attributes for the response
response.setContentType(mimeType);
response.setContentLength(fileLength);
String headerKey = "Content-Disposition";
String headerValue = String.format("attachment; filename=\"%s\"", fileName + ".xml");
response.setHeader(headerKey, headerValue);
// writes the file to the client
OutputStream outStream = response.getOutputStream();
byte[] buffer = new byte[BUFFER_SIZE];
int bytesRead = -1;
while ((bytesRead = inputStream.read(buffer)) != -1) {
outStream.write(buffer, 0, bytesRead);
}
inputStream.close();
outStream.close();
} else {
// no file found
// response.getWriter().print("File not found for the id: " + uploadId);
}
} catch (SQLException ex) {
ex.printStackTrace();
response.getWriter().print("SQL Error: " + ex.getMessage());
} catch (IOException ex) {
ex.printStackTrace();
response.getWriter().print("IO Error: " + ex.getMessage());
} finally {
if (conn != null) {
try {
conn.close();
} catch (SQLException ex) {
Logger.getLogger(BDFileDownloadServlet.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
}
如果您需要更多详细信息，请询问。
【问题讨论】：
标签： jsp servlets parameters load parameter-passing