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Return a zip (or any file) from the server on the client browser (REST)

So I am using Java for my Server and Angular for the Client. I am currently working on a feature where you can select multiple files from a table and when you press on download, it generates a zip file and downloads it to your browser. As of right now, the server now creates the zip file and I can access it in the server files. All that is left to do is to make it download on the client's browser. (the zip file is deleted after the client downloads it)
After doing some research, I found out that you can use a fileOutputStream to do this. I also saw some tools like retrofit... I am using REST and this is what my code looks like. How would I achieve my goal as simply as possible?
Angular
httpGetDownloadZip(target: string[]): Observable<ServerAnswer> {
const params = new HttpParams().set('target', String(target)).set('numberOfFiles', String(target.length));
const headers = new HttpHeaders().set('token', this.tokenService.getStorageToken());
const options = {
headers,
params,
};
return this.http
.get<ServerAnswer>(this.BASE_URL + '/files/downloadZip', options)
.pipe(catchError(this.handleError<ServerAnswer>('httpGetZip')));
}
Java zipping method
public void getDownloadZip(String[] files, String folderName) throws IOException {
[...] // The method is huge but basically I generate a folder called "Download/" in the server
// Zipping the "Download/" folder
ZipUtil.pack(new File("Download"), new File("selected-files.zip"));
// what do I return ???
return;
}
Java context
server.createContext("/files/downloadZip", new HttpHandler() {
#Override
public void handle(HttpExchange exchange) throws IOException {
if (!handleTokenPreflight(exchange)) { return; }
System.out.println(exchange.getRequestURI());
Map<String, String> queryParam = parseQueryParam(exchange.getRequestURI().getQuery());
String authToken = exchange.getRequestHeaders().getFirst("token");
String target = queryParam.get("target") + ",";
String[] files = new String[Integer.parseInt(queryParam.get("numberOfFiles"))];
[...] // I process the data in this entire method and send it to the previous method that creates a zip
Controller.getDownloadZip(files, folderName);
// what do I return to download the file on the client's browser ????
return;
}
});

A possible approach to successfully download your zip file can be the described in the following paragraphs.
First, consider returning a reference to the zip file obtained as the compression result in your downloadZip method:
public File getDownloadZip(String[] files, String folderName) throws IOException {
[...] // The method is huge but basically I generate a folder called "Download/" in the server
// Zipping the "Download/" folder
File selectedFilesZipFile = new File("selected-files.zip")
ZipUtil.pack(new File("Download"), selectedFilesZipFile);
// return the zipped file obtained as result of the previous operation
return selectedFilesZipFile;
}
Now, modify your HttpHandler to perform the download:
server.createContext("/files/downloadZip", new HttpHandler() {
#Override
public void handle(HttpExchange exchange) throws IOException {
if (!handleTokenPreflight(exchange)) { return; }
System.out.println(exchange.getRequestURI());
Map<String, String> queryParam = parseQueryParam(exchange.getRequestURI().getQuery());
String authToken = exchange.getRequestHeaders().getFirst("token");
String target = queryParam.get("target") + ",";
String[] files = new String[Integer.parseInt(queryParam.get("numberOfFiles"))];
[...] // I process the data in this entire method and send it to the previous method that creates a zip
// Get a reference to the zipped file
File selectedFilesZipFile = Controller.getDownloadZip(files, folderName);
// Set the appropiate Content-Type
exchange.getResponseHeaders().set("Content-Type", "application/zip");
// Optionally, if the file is downloaded in an anchor, set the appropiate content disposition
// exchange.getResponseHeaders().add("Content-Disposition", "attachment; filename=selected-files.zip");
// Download the file. I used java.nio.Files to copy the file contents, but please, feel free
// to use other option like java.io or the Commons-IO library, for instance
exchange.sendResponseHeaders(200, selectedFilesZipFile.length());
try (OutputStream responseBody = httpExchange.getResponseBody()) {
Files.copy(selectedFilesZipFile.toPath(), responseBody);
responseBody.flush();
}
}
});
Now the problem is how to deal with the download in Angular.
As suggested in the previous code, if the resource is public or you have a way to manage your security token, including it as a parameter in the URL, for instance, one possible solution is to not use Angular HttpClient but an anchor with an href that points to your ever backend handler method directly.
If you need to use Angular HttpClient, perhaps to include your auth tokens, then you can try the approach proposed in this great SO question.
First, in your handler, encode to Base64 the zipped file contents to simplify the task of byte handling (in a general use case, you can typically return from your server a JSON object with the file content and metadata describing that content, like content-type, etcetera):
server.createContext("/files/downloadZip", new HttpHandler() {
#Override
public void handle(HttpExchange exchange) throws IOException {
if (!handleTokenPreflight(exchange)) { return; }
System.out.println(exchange.getRequestURI());
Map<String, String> queryParam = parseQueryParam(exchange.getRequestURI().getQuery());
String authToken = exchange.getRequestHeaders().getFirst("token");
String target = queryParam.get("target") + ",";
String[] files = new String[Integer.parseInt(queryParam.get("numberOfFiles"))];
[...] // I process the data in this entire method and send it to the previous method that creates a zip
// Get a reference to the zipped file
File selectedFilesZipFile = Controller.getDownloadZip(files, folderName);
// Set the appropiate Content-Type
exchange.getResponseHeaders().set("Content-Type", "application/zip");
// Download the file
byte[] fileContent = Files.readAllBytes(selectedFilesZipFile.toPath());
byte[] base64Data = Base64.getEncoder().encode(fileContent);
exchange.sendResponseHeaders(200, base64Data.length);
try (OutputStream responseBody = httpExchange.getResponseBody()) {
// Here I am using Commons-IO IOUtils: again, please, feel free to use other alternatives for writing
// the base64 data to the response outputstream
IOUtils.write(base64Data, responseBody);
responseBody.flush();
}
}
});
After that, use the following code in you client side Angular component to perform the download:
this.downloadService.httpGetDownloadZip(['target1','target2']).pipe(
tap((b64Data) => {
const blob = this.b64toBlob(b64Data, 'application/zip');
const blobUrl = URL.createObjectURL(blob);
window.open(blobUrl);
})
).subscribe()
As indicated in the aforementioned question, b64toBlob will look like this:
private b64toBlob(b64Data: string, contentType = '', sliceSize = 512) {
const byteCharacters = atob(b64Data);
const byteArrays = [];
for (let offset = 0; offset < byteCharacters.length; offset += sliceSize) {
const slice = byteCharacters.slice(offset, offset + sliceSize);
const byteNumbers = new Array(slice.length);
for (let i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
const byteArray = new Uint8Array(byteNumbers);
byteArrays.push(byteArray);
}
const blob = new Blob(byteArrays, {type: contentType});
return blob;
}
Probably you will need to slightly modify the httpGetDownloadZip method in your service to take into account the returned base 64 data - basically, change ServerAnswer to string as the returned information type:
httpGetDownloadZip(target: string[]): Observable<string> {
const params = new HttpParams().set('target', String(target)).set('numberOfFiles', String(target.length));
const headers = new HttpHeaders().set('token', this.tokenService.getStorageToken());
const options = {
headers,
params,
};
return this.http
.get<string>(this.BASE_URL + '/files/downloadZip', options)
.pipe(catchError(this.handleError<ServerAnswer>('httpGetZip')));
}

You could try using responseType as arraybuffer.
Eg:
return this.http.get(URL_API_REST + 'download?filename=' + filename, {
responseType: 'arraybuffer'
});

In My Project including both front end (angular) and back end (java).
We used the below solution ( hope it work for you ):
Angular:
https://github.com/eligrey/FileSaver.js
let observable = this.downSvc.download(opts);
this.handleData(observable, (data) => {
let content = data;
const blob = new Blob([content], { type: 'application/pdf' });
saveAs(blob, file);
});
Java:
public void download(HttpServletRequest request,HttpServletResponse response){
....
response.setHeader("Content-Disposition",
"attachment;filename=\"" + fileName + "\"");
try (
OutputStream os = response.getOutputStream();
InputStream is = new FileInputStream(file);) {
byte[] buf = new byte[1024];
int len = 0;
while ((len = is.read(buf)) > -1) {
os.write(buf, 0, len);
}
os.flush();
}

You can still use HttpServletRequest on the server...
Then get its OutputStream and write to it.
#RequestMapping(method = RequestMethod.POST , params="action=downloadDocument")
public String downloadDocument(#RequestParam(value="documentId", required=true) String documentId,
HttpServletRequest request,
HttpServletResponse response )
{
try {
String docName = null;
String documentSavePath = getDocumentSavePath();
PDocument doc = mainService.getDocumentById(iDocumentId);
if(doc==null){
throw new RuntimeException("document with id: " + documentId + " not found!");
}
docName = doc.getName();
String path = documentSavePath + ContextUtils.fileSeperator() + docName;
response.setHeader("Content-Disposition", "inline;filename=\"" + docName + "\"");
OutputStream out = response.getOutputStream();
response.setContentType("application/word");
FileInputStream stream = new FileInputStream(path);
IOUtils.copy(stream, out);
out.flush();
out.close();
} catch(FileNotFoundException fnfe){
logger.error("Error downloading document! - document not found!!!! " + fnfe.getMessage() , fnfe);
} catch (IOException e) {
logger.error("Error downloading document!!! " + e.getMessage(),e);
}
return null;
}

Crystal reports creating report from XML and exporting it to PDF without needing path to original XML

I have a Java web application that exports pdf files.
I have to use Crystal Reports 11. I can already export pdfs, the issue is that it only works locally because the .rpt file has a reference to an XML file in my machine.
So, when I want to export a report and the .rpt file can't find the file, even though I'm giving it a new dataset to work with it still throws a not found exception. I tried changing the file's connection programmatically but it always throws an exception related to the connection.
public InputStream export() throws ReportSDKException, IOException, IllegalArgumentException, IllegalAccessException {
ReportClientDocument reportClientDoc = new ReportClientDocument();
reportClientDoc.setLocale(Locale.forLanguageTag(localeTag));
reportClientDoc.open(reportPath, OpenReportOptions._discardSavedData);
DatabaseController databaseController = reportClientDoc.getDatabaseController();
IConnectionInfo oldConn = databaseController.getConnectionInfos(null).get(0);
IConnectionInfo newConn = resolveConnection(reportClientDoc).get(0);
int replaceParams = DBOptions._ignoreCurrentTableQualifiers | DBOptions._doNotVerifyDB;
databaseController.replaceConnection(oldConn, newConn, null,replaceParams);
reportClientDoc.getDatabaseController().setDataSource(this.dataset);
ParameterFieldController parameterController = reportClientDoc.getDataDefController()
.getParameterFieldController();
for (Param<Double> p : doubleParams) {
parameterController.setCurrentValue(p.subReportName, p.fieldName, p.value);
}
for (Param<Object> p : objectParams) {
parameterController.setCurrentValue(p.subReportName, p.fieldName, p.value);
}
return reportClientDoc.getPrintOutputController().export(this.format);
}
private ConnectionInfos resolveConnection(ReportClientDocument reportClientDoc) throws ReportSDKException {
IConnectionInfo oldConnection = new ConnectionInfo();
DatabaseController dbController = reportClientDoc.getDatabaseController();
oldConnection = dbController.getConnectionInfos(null).getConnectionInfo(0);
String xsdPath = Paths.get(this.xsdPath).toAbsolutePath().toString();
final String SERVER_NAME = dummyXmlPath + " " + xsdPath;
final String DATABASE_DLL = oldConnection.getAttributes().getStringValue("Database DLL");
final String LOCAL_SCHEMA_FILE = xsdPath;
final String SERVER_TYPE = "XML";
final String PREQESERVERNAME = SERVER_NAME;
final String PREQESERVERTYPE = "XML";
final String LOCAL_XML_FILE = dummyXmlPath;
PropertyBag newAttributes = new PropertyBag();
newAttributes.put("Server Name", SERVER_NAME);
newAttributes.put("Database DLL", DATABASE_DLL);
newAttributes.put("Local Schema File", LOCAL_SCHEMA_FILE);
newAttributes.put("PreQEServerName", PREQESERVERNAME);
newAttributes.put("PreQEServerType", PREQESERVERTYPE);
newAttributes.put("Server Type", SERVER_TYPE);
newAttributes.put("Local XML File", LOCAL_XML_FILE);
IConnectionInfo newConnection = (IConnectionInfo) oldConnection.clone(true);
newConnection.setAttributes(newAttributes);
newConnection.setKind(oldConnection.getKind());
ConnectionInfos connectionInfos = new ConnectionInfos();
connectionInfos.add(newConnection);
return connectionInfos;
}

I was able to fix this by adding the Subreport data to the subreports.
SubreportController subreportController = reportClientDoc.getSubreportController();
for (String string : subreportController.querySubreportNames()) {
subreportController.setDataSource(string, dataset);
}

Formatting header field for bean generator - Java

I have written a program that parses a csv file and creates a bean from the data to be put into a database. Everything works perfectly however now that this will be moved out of a testing environment, the real header names from the csv's will have to be added. These headers contain spaces and /. I am searching for a way to allow my parser to read these headers. When I define the header names, I have to use camelCasing and I am unable to insert spaces or other characters. Is there anyway to alter this?
Here is my constructor(integrationTeam needs to be Integration Team, softwareHardware needs to be Hardware/Software -- as is in csv header)
public class BeanGen {
public BeanGen(
final String name,
final String manufacturer,
final String model,
final String owner,
final String integrationTeam,
final String shipping,
final String hardwareSoftware,
final String subsystem,
final String plane,
final String integrationStandalone,
final String integrationInterface,
final String function,
final String helpLinks,
final String installationInstructions,
final String testSteps,
final String leadEngineer)
{
this.name = name;
this.manufacturer = manufacturer;
this.model = model;
this.owner = owner;
this.integrationTeam = integrationTeam;
this.shipping = shipping;
this.hardwareSoftware = hardwareSoftware;
this.subsystem = subsystem;
this.plane = plane;
this.integrationStandalone = integrationStandalone;
this.integrationInterface = integrationInterface;
this.function = function;
this.helpLinks = helpLinks;
this.installationInstructions = installationInstructions;
this.testSteps = testSteps;
this.leadEngineer = leadEngineer;
}
Here is the parser that handles the constructor
public class ParseHandler {
private static CellProcessor[] getProcessors() {
final CellProcessor[] processors = new CellProcessor[] {
new Optional(),
new Optional(),
new Optional(),
new Optional(),
new Optional(),
new Optional(),
new Optional(),
new Optional(),
new Optional(),
new Optional(),
new Optional(),
new Optional(),
new Optional(),
new Optional(),
new Optional(),
new Optional(),
};
return processors;
}
public static BeanGen readWithCsvBeanReader(Path path) throws IOException {
ICsvBeanReader beanReader = null;
BeanGen projectBean = null;
System.out.println("Processing File: " + path);
try {
beanReader = new CsvBeanReader(new FileReader(path.toString()), CsvPreference.STANDARD_PREFERENCE);
// the header elements are used to map the values to the bean (names
// must match)
final String[] header = beanReader.getHeader(true);
final CellProcessor[] processors = getProcessors();
if ((projectBean = beanReader.read(BeanGen.class, header, processors)) != null) {
System.out.println(String.format("%s", projectBean.toString()));
}
} finally {
if (beanReader != null) {
beanReader.close();
}
} return projectBean;
}
}

See the Super CSV documentation, section Reading with CsvBeanReader:
This relies on the fact that the column names in the header of the CSV file [...] match up exactly with the bean's field names, and the bean has the appropriate setters defined for each field.
If your header doesn't match (or there is no header), then you can simply define your own name mapping array.
You read the header and pass it to beanReader.read() as the second parameter. But according to the API reference the second parameter is a string array containing the bean property names. So you should pass something like
new String[] { "name", "manufacturer", "model", "owner", "integrationTeam", ... }
as the second parameter. So the first CSV column matches to bean field name, the second field matches to bean field manufacturer, etc.

Post multipart form with google-http-java-client

It's not clear from the google-http-java-client* docs how you would go about posting a form that has a file field.
For example I'm trying to print a document using the Google Cloud Print API:
HttpRequestFactory httpRequestFactory = getHttpRequestFactory();
Map<String, Object> parameters = Maps.newHashMap();
parameters.put("printerId", printRequest.getPrinterId());
parameters.put("title", printRequest.getTitle());
parameters.put("contentType", printRequest.getContentType());
parameters.put("ticket", new Gson().toJson(printRequest.getOptions()));
MultipartContent content = new MultipartContent();
content.addPart(new MultipartContent.Part(new UrlEncodedContent(parameters)));
content.addPart(new MultipartContent.Part(
new FileContent(printRequest.getContentType(), printRequest.getFile())));
try {
HttpResponse response = httpRequestFactory.buildPostRequest(
SubmitUrl, content).execute();
System.out.println(IOUtils.toString(response.getContent()));
} catch (IOException e) {
String message = String.format();
System.out.println("Error submitting print job: " + e.getMessage());
}
Unfortunately this doesn't work. The API returns the error "Printer Id required for this request." which seems to me like the request isn't properly formed.
What am I doing wrong?
* I'm specifically using the google-http-java-client as it handles automatic refreshing of OAuth tokens etc for me. Please don't reply with solutions that involve using other HTTP clients.

So it looks like I misunderstood how form fields are added to multipart messages. The working code now looks like this
HttpRequestFactory httpRequestFactory = getHttpRequestFactory(username);
Map<String, String> parameters = Maps.newHashMap();
parameters.put("printerid", printRequest.getPrinterId());
parameters.put("title", printRequest.getTitle());
parameters.put("contentType", printRequest.getContentType());
// Map print options into CJT structure
Map<String, Object> options = Maps.newHashMap();
options.put("version", "1.0");
options.put("print", printRequest.getOptions());
parameters.put("ticket", new Gson().toJson(options));
// Add parameters
MultipartContent content = new MultipartContent().setMediaType(
new HttpMediaType("multipart/form-data")
.setParameter("boundary", "__END_OF_PART__"));
for (String name : parameters.keySet()) {
MultipartContent.Part part = new MultipartContent.Part(
new ByteArrayContent(null, parameters.get(name).getBytes()));
part.setHeaders(new HttpHeaders().set(
"Content-Disposition", String.format("form-data; name=\"%s\"", name)));
content.addPart(part);
}
// Add file
FileContent fileContent = new FileContent(
printRequest.getContentType(), printRequest.getFile());
MultipartContent.Part part = new MultipartContent.Part(fileContent);
part.setHeaders(new HttpHeaders().set(
"Content-Disposition",
String.format("form-data; name=\"content\"; filename=\"%s\"", printRequest.getFile().getName())));
content.addPart(part);
try {
HttpResponse response = httpRequestFactory.buildPostRequest(
SubmitUrl, content).execute();
System.out.println(IOUtils.toString(response.getContent()));
} catch (IOException e) {
...
}
The most important parts above were overriding the default HttpMediaType to specify "multipart/form-data" and adding each field as its own part with a "Content-Disposition" header to designate the form field name.

Spring - validate that all message resources are well configured

We need to add some code to be executed on application load in order to validate that all the messages.properties elements are well defined for all languages.
Is this possible?
Steps: dynamically read on application load all the spring message codes from JSP or java classes then pass through all message resources properties files and validate that nothing is missing from them.

We ended up doing this manually but without using any library.
Steps:
have all the keys used in Java classes or JSP defined in a constant file
Read them using Java .class properties:
Field[] fields = Constants.class.getFields();
String filed[i].get(Constants.class);
Read all messageResources.properties file names from the project using:
String pathToThisClass = MessageResourcesValidator.class.getProtectionDomain().getCodeSource().getLocatin().getPath();
File filePath = new File(pathToThisClass);
String[] list = filePath.list(new DirFilter("(messages).*\\.(properties)"));
DirFilter is a normal class implementing Java's FileNameFilter
Create a class that read the properties from a file using its file name:
public class PropertiesFile{
private Properties prop;
public PropertiesFile(String fileName) throws Exception
{
init(fileName);
}
private void init(String fileName) throws Exception
{
prop = new Properties();
try (InputStream input = getClass().getClassLoader().getResourceAsStream(fileName);)
{
if(input == null)
{
throw new Exception("Enable to load properties file " + fileName);
}
prop.load(input);
}
catch(IOException e)
{
throw new Exception("Error loading properties file " + fileName);
}
}
public List<String> getPropertiesKeysList()
{
List<String> result = new ArrayList<>();
Enumeration<?> e = prop.propertyNames();
while(e.hasMoreElements())
{
result.add((String) e.nextElement());
// String value = prop.getProperty(key);
}
return result;
}
}
The part that does the comparison should be something as the following code that calls the above methods:
List<String> msgResourcesFiles = getMessageResourcesFileNames();
List<String> codeKeys = getListOfCodeMessageResources();
PropertiesFile file = null;
List<String> propKeys = null;
for(String fileName : msgResourcesFiles)
{
file = new PropertiesFile(fileName);
propKeys = file.getPropertiesKeysList();
for(String key : codeKeys)
{
if(!propKeys.contains(key))
{
throw new Exception("Missing key " + key);
}
}
}
Note: or another workaround would be to compare all message resources files to a default one and this way we minimize the code needed from the above explanation.