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How to output a temporary file in API service in Java, and delete it in the end?

I am writing an API service that fetches data from a stream, and outputs it in a file. I can't output it as a stream because I use Swagger (now OpenAPI) 2.0, which doesn't support output streams (Swagger 3.0 does, but i can't use it).
What would be the cleanest way to make a file, output it via the service, and then make sure it gets deleted?
I initially thought I might use a temp file and delete in finally clause. However, there is no guarantee that the file finished downloading on the client side before that clause is reached and file is deleted.
Am I right? Wrong? Is there a better way to do this?

I was talking about using a closeable in the comments. This is it.
Usage:
try (TempFile file = new TempFile("tempfile", ".txt")) {
// do stuff with file
} catch (IOException e) {
// error handling.
// file should be automatically deleted.
}
TempFile:
public class TempFile implements AutoCloseable {
private final File file;
public TempFile(String prefix, String suffix) {
this.file = File.createTempFile(prefix, suffix);
}
public File getFile() {
return this.file;
}
#Override
public void close() throws IOException {
this.file.delete();
}
}

File transfer over HTTP using camel

I'm trying to set up a Camel route for transferring files over HTTP. I'm also trying to understand the concept as I'm new to this.
When I code something like below, does that mean I'm routing a simple message over HTTP? Could I call Jetty the consumer in this case? I'm able to run the below code and call the browser and see the message successfully.
from("jetty://http://localhost:32112/greeting")
.setBody(simple("Hello, world!"));
However, I want to send a simple message(eventually an XML) over HTTP following which I would want to save it on disk and analyse it further. Should the code like below work?
CamelContext context = new DefaultCamelContext();
ProducerTemplate template = context.createProducerTemplate();
template.sendBody("direct:start", "This is a test message");
from("direct:start")
.to("jetty://localhost:32112/greeting");
from("jetty://http://localhost:32112/greeting")
.to("direct:end");
Should I be not using direct:start here for parsing XMLs?
Thanks a lot for the help.

first you have to create your routes and start your context. Then you can send messages via your template.
The route could look like this
from("jetty:http://0.0.0.0:32112/greeting")
.routeId("xml-converter-route").autoStartup(false)
.bean(xmlConverterBean, "convertXmlMethodToBeCalledInBean()")
;

If you just want to transfer data and nothing else use restlet or netty-http4. More lightweight than jetty.
from("restlet:/http://localhost:32112/greeting").convertBodyTo(String.class).log(LoggingLevel.INFO, "filetransfer", "log of body: ${body} and headers ${headers}").to("file://C:/test?fileName=body.txt");

Here's a camel test which may help you understand how these components work.
public class CamelRESTExampleTest extends CamelTestSupport {
Logger LOG = LoggerFactory.getLogger(CamelRESTExampleTest.class);
#Override
protected RouteBuilder createRouteBuilder() {
return new RouteBuilder() {
public void configure() {
// Create a service listening on port 8080
from("restlet:http://localhost:8080/xmlFileService?restletMethod=post")
.process(new Processor() {
public void process(Exchange exchange) throws Exception {
String rawXML = exchange.getIn().getBody(String.class);
LOG.info("rawXML=" + rawXML);
}
});
// Read files from the local directory and send to the service.
// Create a test.xml file in this directory and it will be read in
from("file:src/test/resources/data?noop=true")
.to("restlet:http://localhost:8080/xmlFileService?restletMethod=post");
}
};
}
#Test
public void test() throws InterruptedException {
// Give the route time to complete
TimeUnit.SECONDS.sleep(5);
}
}

'File#renameTo()' does not work in java

I'm trying to rename an existing file using File#renameTo(), but it doesn't seem to work.
The following code represents what I am trying to do:
public class RenameFileDirectory {
public static void main(String[] args) throws IOException {
new RenameFileDirectory();
}
public RenameFileDirectory() throws IOException {
File file = new File("C:\\Users\\User-PC\\Desktop\\Nouveau dossier2\\file.png");
File desFile = new File ("C:\\Users\\User-PC\\Desktop\\Nouveau dossier2\\file2.png");
if (file.renameTo(desFile)) {
System.out.println("successful rename");
} else {
System.out.println("error");
}
}
}

Try using Files.move instead. If you read the javadocs for renameTo, it states that:
Many aspects of the behavior of this method are inherently platform-dependent: The rename operation might not be able to move a file from one filesystem to another, it might not be atomic, and it might not succeed if a file with the destination abstract pathname already exists. The return value should always be checked to make sure that the rename operation was successful.

How to watch file for new content and retrieve that content

I have a file with name foo.txt. This file contains some text. I want to achieve following functionality:
I launch program
write something to the file (for example add one row: new string in foo.txt)
I want to get ONLY NEW content of this file.
Can you clarify the best solution of this problem? Also I want resolve related issues: in case if I modify foo.txt I want to see diff.
The closest tool which I found in Java is WatchService but if I understood right this tool can only detect type of event happened on filesystem (create file or delete or modify).

Java Diff Utils is designed for that purpose.
final List<String> originalFileContents = new ArrayList<String>();
final String filePath = "C:/Users/BackSlash/Desktop/asd.txt";
FileListener fileListener = new FileListener() {
#Override
public void fileDeleted(FileChangeEvent paramFileChangeEvent)
throws Exception {
// use this to handle file deletion event
}
#Override
public void fileCreated(FileChangeEvent paramFileChangeEvent)
throws Exception {
// use this to handle file creation event
}
#Override
public void fileChanged(FileChangeEvent paramFileChangeEvent)
throws Exception {
System.out.println("File Changed");
//get new contents
List<String> newFileContents = new ArrayList<String> ();
getFileContents(filePath, newFileContents);
//get the diff between the two files
Patch patch = DiffUtils.diff(originalFileContents, newFileContents);
//get single changes in a list
List<Delta> deltas = patch.getDeltas();
//print the changes
for (Delta delta : deltas) {
System.out.println(delta);
}
}
};
DefaultFileMonitor monitor = new DefaultFileMonitor(fileListener);
try {
FileObject fileObject = VFS.getManager().resolveFile(filePath);
getFileContents(filePath, originalFileContents);
monitor.addFile(fileObject);
monitor.start();
} catch (InterruptedException ex) {
ex.printStackTrace();
} catch (FileNotFoundException e) {
//handle
e.printStackTrace();
} catch (IOException e) {
//handle
e.printStackTrace();
}
Where getFileContents is :
void getFileContents(String path, List<String> contents) throws FileNotFoundException, IOException {
contents.clear();
BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(path), "UTF-8"));
String line = null;
while ((line = reader.readLine()) != null) {
contents.add(line);
}
}
What I did:
I loaded the original file contents in a List<String>.
I used Apache Commons VFS to listen for file changes, using FileMonitor. You may ask, why? Because WatchService is only available starting from Java 7, while FileMonitor works with at least Java 5 (personal preference, if you prefer WatchService you can use it). note: Apache Commons VFS depends on Apache Commons Logging, you'll have to add both to your build path in order to make it work.
I created a FileListener, then I implemented the fileChanged method.
That method load new contents form the file, and uses Patch.diff to retrieve all differences, then prints them
I created a DefaultFileMonitor, which basically listens for changes to a file, and I added my file to it.
I started the monitor.
After the monitor is started, it will begin listening for file changes.

Camel file unit test

I am new to Apache Camel, I have written a simple route to scan a directory (/test), file will be processed when it was copied into the directory. Anyone has an idea on how to write a camel unit test to test the following route? Is there a way to mock the process of copying the file into the /test directory so that the route will be triggered.
public void configure() {
from( "file:/test?preMove=IN_PROGRESS" +
"&move=completed/${date:now:yyyyMMdd}/${file:name}" +
"&moveFailed=FAILED/${file:name.noext}-${date:now:yyyyMMddHHmmssSSS}.${file:ext}" )
.process(new Processor() {
public void process(Exchange exchange) throws IOException {
File file = (File) exchange.getIn().getBody();
// read file content ......
}
});
}

You have done the routing by one of many correct ways. But there exist some more important pieces to make your code run - you should create a context, create a router with this your configure(), add it to a context, and run this context.
Sorry, I prefer beans to processors, so you have also to register a bean. And make you processing a normal named method in a named class.
I think, the most compact info is here. JUnit test is a standalone app and you need to run Camel as a standalone app for JUnit testing.

I think the basic idea is that you mock the end endpoint so you can check what is coming out your route. There are a few different ways, but you could test your route as follows:
public class MyRouteTest extends CamelSpringTestSupport {
private static final String INPUT_FILE = "myInputFile.xml";
private static final String URI_START = "direct:start";
private static final String URI_END = "mock:end";
#Override
public boolean isUseAdviceWith() {
return true;
}
#Override
protected AbstractApplicationContext createApplicationContext() {
return new AnnotationConfigApplicationContext(CamelTestConfig.class); // this is my Spring test config, where you wire beans
}
#Override
protected RouteBuilder createRouteBuilder() {
MyRoute route = new MyRoute();
route.setFrom(URI_START); // I have added getter and setters to MyRoute so I can mock 'start' and 'end'
route.setTo(URI_END);
return route;
}
#Test
public void testMyRoute() throws Exception {
MockEndpoint result = getMockEndpoint(URI_END);
context.start();
// I am just checking I receive 5 messages, but you should actually check the content with expectedBodiesReceived() depending on what your processor does to the those files.
result.expectedMessageCount(5);
// I am just sending the same file 5 times
for (int i = 0; i < 5; i++) {
template.sendBody(URI_START, getInputFile(INPUT_FILE));
}
result.assertIsSatisfied();
context.stop();
}
private File getInputFile(String name) throws URISyntaxException, IOException {
return FileUtils.getFile("src", "test", "resources", name);
}
I am sure you already solved your issue is 2013, but this is how I would solve it in 2017. Regards