【发布时间】：2014-08-22 14:30:38
【问题描述】：
我不太熟悉如何使用 Java 将文件输出回客户端。我正在尝试创建一个 CSV 文件以发送回客户端并在 Excel 中打开。
我为服务器端创建找到了this tool。我不确定如何使用它来返回实际文件。 Here 是我用来返回 txt 文件的代码示例，我认为我可以使用部分响应，但我不再获取文件，因为我正在创建这个 CSV，所以我不确定我能用什么。
在下面的代码中，我最大的问题是我必须使用控制器返回什么以及如何完成它？我不确定在这之间以及从 CSV 编写器到控制器之间我需要返回什么。任何帮助，将不胜感激。
到目前为止，这是我的代码：
控制器：
@RequestMapping(value = "/web/csvexport", method = RequestMethod.POST)
protected void processCSV(HttpServletRequest request, HttpServletResponse response, @RequestBody String jsonRequest)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
try {
CSVWriter csvWriter = new CSVWriter();
JsonFlattener jsonFlattener = new JsonFlattener();
String fileName = "StandardQuery";
csvWriter.writeAsCSV(jsonFlattener.parseJson(jsonRequest), fileName);
} catch (Exception e) {
System.out.println("Exception: " + e);
}
}
CVS 编写器：
public class CSVWriter {
public void writeAsCSV(List<Map<String, String>> flatJson, String fileName) throws FileNotFoundException {
Set<String> headers = collectHeaders(flatJson);
String output = StringUtils.join(headers.toArray(), ",") + "\n";
for (Map<String, String> map : flatJson) {
output = output + getCommaSeperatedRow(headers, map) + "\n";
}
writeToFile(output, fileName);
}
private void writeToFile(String output, String fileName) throws FileNotFoundException {
BufferedWriter writer = null;
try {
writer = new BufferedWriter(new FileWriter(fileName));
writer.write(output);
} catch (IOException e) {
e.printStackTrace();
} finally {
close(writer);
}
}
private void close(BufferedWriter writer) {
try {
if (writer != null) {
writer.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
private String getCommaSeperatedRow(Set<String> headers, Map<String, String> map) {
List<String> items = new ArrayList<String>();
for (String header : headers) {
String value = map.get(header) == null ? "" : map.get(header).replace(",", "");
items.add(value);
}
return StringUtils.join(items.toArray(), ",");
}
private Set<String> collectHeaders(List<Map<String, String>> flatJson) {
Set<String> headers = new TreeSet<String>();
for (Map<String, String> map : flatJson) {
headers.addAll(map.keySet());
}
return headers;
}
}
Json 扁平化器：
public class JsonFlattener {
public Map<String, String> parse(JSONObject jsonObject) {
Map<String, String> flatJson = new HashMap<String, String>();
flatten(jsonObject, flatJson, "");
return flatJson;
}
public List<Map<String, String>> parse(JSONArray jsonArray) {
List<Map<String, String>> flatJson = new ArrayList<Map<String, String>>();
int length = jsonArray.length();
for (int i = 0; i < length; i++) {
JSONObject jsonObject = jsonArray.getJSONObject(i);
Map<String, String> stringMap = parse(jsonObject);
flatJson.add(stringMap);
}
return flatJson;
}
public List<Map<String, String>> parseJson(String json) throws Exception {
List<Map<String, String>> flatJson = null;
try {
JSONObject jsonObject = new JSONObject(json);
flatJson = new ArrayList<Map<String, String>>();
flatJson.add(parse(jsonObject));
} catch (JSONException je) {
flatJson = handleAsArray(json);
}
return flatJson;
}
private List<Map<String, String>> handleAsArray(String json) throws Exception {
List<Map<String, String>> flatJson = null;
try {
JSONArray jsonArray = new JSONArray(json);
flatJson = parse(jsonArray);
} catch (Exception e) {
throw new Exception("Json might be malformed");
}
return flatJson;
}
private void flatten(JSONArray obj, Map<String, String> flatJson, String prefix) {
int length = obj.length();
for (int i = 0; i < length; i++) {
if (obj.get(i).getClass() == JSONArray.class) {
JSONArray jsonArray = (JSONArray) obj.get(i);
if (jsonArray.length() < 1) continue;
flatten(jsonArray, flatJson, prefix + i);
} else if (obj.get(i).getClass() == JSONObject.class) {
JSONObject jsonObject = (JSONObject) obj.get(i);
flatten(jsonObject, flatJson, prefix + (i + 1));
} else {
String value = obj.getString(i);
if (value != null)
flatJson.put(prefix + (i + 1), value);
}
}
}
private void flatten(JSONObject obj, Map<String, String> flatJson, String prefix) {
Iterator iterator = obj.keys();
while (iterator.hasNext()) {
String key = iterator.next().toString();
if (obj.get(key).getClass() == JSONObject.class) {
JSONObject jsonObject = (JSONObject) obj.get(key);
flatten(jsonObject, flatJson, prefix);
} else if (obj.get(key).getClass() == JSONArray.class) {
JSONArray jsonArray = (JSONArray) obj.get(key);
if (jsonArray.length() < 1) continue;
flatten(jsonArray, flatJson, key);
} else {
String value = obj.getString(key);
if (value != null && !value.equals("null"))
flatJson.put(prefix + key, value);
}
}
}
}
这是我从中调用控制器的服务。我之前用它来返回一个 .txt 文件，所以我不确定它的可用性如何，但我认为如果我将文件流回它会处理它......：
getFile: function(jsonObj, fileName) {
var _defer = $q.defer();
$http.post("/web/csvexport/", jsonObj).success(function(data, status, headers) {
var octetStreamMime = "application/octet-stream";
// Get the headers
headers = headers();
// Get the filename from the x-filename header or default to "download.bin"
//var filename = headers["x-filename"] || "logfile.log";
var filename = fileName;
// Determine the content type from the header or default to "application/octet-stream"
var contentType = headers["content-type"] || octetStreamMime;
if(navigator.msSaveBlob)
{
// Save blob is supported, so get the blob as it's contentType and call save.
var blob = new Blob([data], { type: contentType });
navigator.msSaveBlob(blob, filename);
console.log("SaveBlob Success");
}
else
{
// Get the blob url creator
var urlCreator = window.URL || window.webkitURL || window.mozURL || window.msURL;
if(urlCreator)
{
// Try to use a download link
var link = document.createElement("a");
if("download" in link)
{
// Prepare a blob URL
var blob = new Blob([data], { type: contentType });
var url = urlCreator.createObjectURL(blob);
link.setAttribute("href", url);
// Set the download attribute (Supported in Chrome 14+ / Firefox 20+)
link.setAttribute("download", filename);
// Simulate clicking the download link
var event = document.createEvent('MouseEvents');
event.initMouseEvent('click', true, true, window, 1, 0, 0, 0, 0, false, false, false, false, 0, null);
link.dispatchEvent(event);
console.log("Download link Success");
} else {
// Prepare a blob URL
// Use application/octet-stream when using window.location to force download
var blob = new Blob([data], { type: octetStreamMime });
var url = urlCreator.createObjectURL(blob);
window.location = url;
console.log("window.location Success");
}
} else {
console.log("Not supported");
}
}
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标签： java json angularjs csv servlets