我试图通过Java Servlet从我的服务器下载文件。 我遇到的问题是，当我直接输入servlet url（https://localhost:8443/SSP/settings?type=db_backup）时，我得到servlet来执行其代码并通过下载对话框提示我。
但我想通过Javascript调用servlets的doGet方法，用一些进度条包装它。
此处出现问题：servlet中的代码已执行但我没有获得该文件的下载提示。
我的代码到目前为止：
HTML：
<!-- Solution #1 -->
<button class="btn_do_db_backup" type="button">DB-Backup #1</button>
<!-- Solution #2 -->
<form action="/SSP/settings?type=db_backup" method="GET">
<button type="submit">DB-Backup #2</button></br>
</form>
JS：
// Solution #1
$(".btn_do_db_backup").click(function(e){
e.preventDefault();
$.get("settings?type=db_backup", function(data){
if(data != ""){
//further coding
}
});
// Having the code below works but doesnt
// give me the chance to wrap the call with a loading animation
//document.location = "/SSP/settings?type=db_backup";
});
的Servlet
@Override
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
// PART 1
// execute srcipt to generate file to download later on
StringBuffer output = new StringBuffer();
ProcessBuilder builder = new ProcessBuilder("cmd.exe", "/c", "D:\\TEMP\\sql_dump.cmd");
builder.redirectErrorStream(true);
Process p = builder.start();
BufferedReader r = new BufferedReader(new InputStreamReader(p.getInputStream()));
String line = "";
String filename = "";
int tmp = 0;
while (true) {
line = r.readLine();
if (line == null) { break; }
output.append(line + "\n");
// code for finding filename not optimal but works for now -> redo later on
if(tmp == 1){
filename = line.substring(line.indexOf("db_backup_"), line.indexOf('"', line.indexOf("db_backup_")) );
}
tmp++;
}
// PART 2
// download the file generated above
OutputStream out = response.getOutputStream();
String filepath = "D:\\TEMP\\sql_dump\\";
response.setContentType("APPLICATION/OCTET-STREAM");
response.setHeader("Content-Disposition", "attachment;filename=\"" + filename + "\"");
FileInputStream fileInputStream = new FileInputStream(filepath + filename);
int i;
while ((i = fileInputStream.read()) != -1) {
out.write(i);
}
out.close();
fileInputStream.close();
}
解决方案＃2效果很好，我得到一个弹出窗口来下载文件。
解决方案＃1调用servlet doGet方法（通过上面的JS代码，我的servlet中的代码正确执行）但我没有下载弹出窗口
我想使用解决方案＃1，因为这让我有机会用加载动画包装$.post调用。
在解决方案＃1中我缺少什么才能让下载弹出窗口进行购物？
编辑1：
我发现data函数中的$.get()填充了所需文件的内容。我现在可以在div中显示.txt文件的内容，但我想重新载入.txt文件。
编辑2：
解决了它，请参阅下面的答案以获取详细信息。如果您认为可以更好地完成评论/评论
答案 0 :(得分：0)
经过一段时间试图让它发挥作用后，我找到了一个有效的解决方案。可能会有更好的，但那就是我提出的那个。
希望这对其他人也有帮助。
我在这里做的基本解释：
所以不用多说了，这里我们使用 flow ...代码：）
<强> HTML：
<form id="form_download_db_backup">
<input type="submit" value="Create & Download DB-Backup"></br>
<a download="" id="downloadlink" style="display: none">download</a>
</form>
<div class="db_backup_result" id="db_backup_result" style="display: none;">
</br>Commandline-Output</br>
<textarea id ="txta_db_backup_result" rows="4" cols="50"></textarea>
</div>
<强> JS：
$("#form_download_db_backup").submit(function(e){
e.preventDefault();
var spinner = new Spinner().spin();
var target = document.getElementById('content');
target.appendChild(spinner.el);
$.ajax({
url:'settings?type=db_backup',
type:'get',
success:function(data){
spinner.stop();
if(data != ""){
var str_data = "" + data;
// Cut commanline output from data
var commandline_output = str_data.substring( 0, str_data.indexOf("--End") );
//show commanline output in textarea
$("#txta_db_backup_result").html(commandline_output);
// Cut content of db_backup file from data
var sql_dump_content = str_data.substring( str_data.indexOf("--sql_d_s--") + 13,str_data.indexOf("--sql_d_e--") );//|
// Cut filename from data
var filename = str_data.substring( str_data.indexOf("--sql_d_fns--") + 15,str_data.indexOf("--sql_d_fne--") - 2 );
//-------------------------------------------------------------
// Prepare download of backupfile
var link = document.getElementById('downloadlink');
var textFile = null;
var blob_data = new Blob([sql_dump_content], {type: 'text/plain'});
// FOR IE10+ Compatibility
if(window.navigator.msSaveOrOpenBlob) {
window.navigator.msSaveBlob(blob_data, filename);
}
// If we are replacing a previously generated file we need to
// manually revoke the object URL to avoid memory leaks.
if (textFile !== null) {
window.URL.revokeObjectURL(textFile);
}
textFile = window.URL.createObjectURL(blob_data);
link.href = textFile;
link.download = filename;
//link.style.display = 'block'; // Use this to make download link visible for manual download
link.click(); // Use this to start download automalically
//-------------------------------------------------------------
// show div containing commandline output & (optional) downloadlink
document.getElementById("db_backup_result").style.display = 'block';
}
}
});
});
<强>的Java小服务程序：
@Override
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
String type = request.getParameter("type");
if(null != type)switch (type) {
case "db_backup":
ServletOutputStream out = response.getOutputStream();
// Prepare multipart response
response.setContentType("multipart/x-mixed-replace;boundary=End");
// Start: First part of response ////////////////////////////////////////////////////////////////////////
// execute commandline script to backup the database
ProcessBuilder builder = new ProcessBuilder("cmd.exe", "/c", "D:\\TEMP\\sql_dump.cmd");
builder.redirectErrorStream(true);
Process p = builder.start();
BufferedReader r = new BufferedReader(new InputStreamReader(p.getInputStream()));
String line = "";
String filename = "";
int tmp = 0;
while (true) {
line = r.readLine();
if (line == null) { break; }
// code for finding filename not optimal but works for now -> redo later on
if(tmp == 1){
filename = line.substring(line.indexOf("db_backup_"), line.indexOf('"', line.indexOf("db_backup_")) );
}
else{
line = line.replace("\u201E", "\'"); // replaces the lowercase " (DOUBLE LOW-9 QUOTATION MARK)
line = line.replace("\u201C", "\'"); // replaces the uppercase " (LEFT DOUBLE QUOTATION MARK)
}
out.println(line);
tmp++;
}
// End: First part of response ////////////////////////////////////////////////////////////////////////
// Separator of firt & second part
out.println("--End");
out.flush();
// Add filename in response (name of download file)
out.println("--sql_d_fns--"); // separator for filename (used to extract filename from response data)
out.println(filename);
out.println("--sql_d_fne--"); // separator for filename (used to extract filename from response data)
// Start: Second part of response ////////////////////////////////////////////////////////////////////////
out.println("--sql_d_s--"); // separator for content of db-dump (this is the text thats going to be downloaded later on)
String filepath = "D:\\TEMP\\sql_dump\\";
FileInputStream fileInputStream = new FileInputStream(filepath + filename);
int i;
while ((i = fileInputStream.read()) != -1) {
out.write(i);
}
out.println("--sql_d_e--"); // separator for content of db-dump (this is the text thats going to be downloaded later on)
// End: Second part of response ////////////////////////////////////////////////////////////////////////
// End the multipart response
out.println("--End--");
out.flush();
break;
default:
break;
}
}
postgreSQL转储包含＆＃34;小写＆＃34; ＆安培; ＆＃34;大写＆＃34;我必须替换的引号。我在这里放了一个链接，以防有人和他们挣扎。他们对那里列出的那些角色有多种编码。