What I'm trying to do is to convert an object to xml, then use a String to transfer it via Web Service so another platform (.Net in this case) can read the xml and then deparse it into the same object. I've been reading this article:
http://simple.sourceforge.net/download/stream/doc/tutorial/tutorial.php#start
And I've been able to do everything with no problems until here:
Serializer serializer = new Persister();
PacienteObj pac = new PacienteObj();
pac.idPaciente = "1";
pac.nomPaciente = "Sonia";
File result = new File("example.xml");
serializer.write(pac, result);
I know this will sound silly, but I can't find where Java creates the new File("example.xml"); so I can check the information.
And I wanna know if is there any way to convert that xml into a String instead of a File, because that's what I need exactly. I can't find that information at the article.
Thanks in advance.
And I wanna know if is there any way to convert that xml into a String instead of a File, because that's what I need exactly. I can't find that information at the article.
Check out the JavaDoc. There is a method that writes to a Writer, so you can hook it up to a StringWriter (which writes into a String):
StringWriter result = new StringWriter(expectedLength);
serializer.write(pac, result)
String s = result.toString();
You can use an instance of StringWriter:
Serializer serializer = new Persister();
PacienteObj pac = new PacienteObj();
pac.idPaciente = "1";
pac.nomPaciente = "Sonia";
StringWriter result = new StringWriter();
serializer.write(pac, result);
String xml = result.toString(); // xml now contains the serialized data
Log or print the below statement will tell you where the file is on the file system.
result.getAbsolutePath()
Related
I am trying to use Jackson streaming API to deserialize huge objects from XML. The idea is to combine streaming API and ObjectMapper to parse XML(or JSON) by small chunks. However I see some inconsistent behavior with XML Parser.
With this code snippet:
try {
String xml1 = "<?xml version=\"1.0\" encoding=\"UTF-8\"?><foo></foo>";
String xml2 = "<?xml version=\"1.0\" encoding=\"UTF-8\"?><foo><bar></bar></foo>";
XmlFactory xmlFactory = new XmlFactory();
JsonParser jp = xmlFactory.createParser(new ByteArrayInputStream(xml1.getBytes()));
JsonToken token = jp.nextToken();
while (token != null) {
System.out.println("xml1 token=" + token);
token = jp.nextToken();
}
jp = xmlFactory.createParser(new ByteArrayInputStream(xml2.getBytes()));
token = jp.nextToken();
while (token != null) {
System.out.println("xml2 token=" + token);
token = jp.nextToken();
}
} catch (IOException e) {
e.printStackTrace();
}
I am getting:
xml1 token=START_OBJECT
xml1 token=END_OBJECT
xml2 token=START_OBJECT
xml2 token=FIELD_NAME
xml2 token=VALUE_NULL
xml2 token=END_OBJECT
Why is the FIELD_NAME token missing for xml1? Why is there just one START_OBJECT token for the second xml? Is there any setting that would allow me to see FIELD_NAME of outer tag?
Problem is quite simple: XML module is different from most other Jackson dataformat modules in that direct access via Streaming API is not supported.
This is mentioned on project README (along with mention that "tree model" is similarly not supported).
Not supported does not necessarily mean "can not be used at all", just that its behavior is different from handling for JSON so callers really need to know what they are doing above and beyond API used for JSON content (and Smile, CBOR, YAML -- even CSV content is represented in a way that is compatible with JSON access).
While you can try to use XmlFactory and streaming parser/generator, its behavior is controlled by XmlMapper based on metadata from Java classes, to make things works correctly via databinding API (that is, XmlMapper).
With that, the reason for observed tokens is that such translation is necessary to map to expected Java object structure:
public class Foo {
public Bar bar;
}
which would map to JSON like:
json
{
"bar" : null
}
as well as XML of
xml
<foo>
<bar></bar>
</foo>
Another way to put this is that XML and JSON data models are fundamentally different, and they can not be trivially translated. Since Jackson's token model is based on JSON, some work is needed to translated XML elements and attributes into structure that equivalent JSON would have.
Above is not to say that what you try to do is impossible. There are 2 ways you might be able to make things work:
Knowing translation that XmlParser does, call getToken() expecting translation
Instead of using XmlParser directly, construct XMLStreamReader (Stax low-level streaming parser), read "raw" tokens, and construct separate XmlParser (via XmlFactory) at expected location, use that for reading.
I hope this helps.
A kid with a hammer...
I don't know much about Jackson; in fact, I just started using it, thinking of using JSON or YAML instead of XML. But for XML, we have been using XStream with success.
//Consumer side
FileInputStream fis = new FileInputStream(filename);
XStream xs = new XStream();
Object obj = xs.fromXML(fis);
fis.close();
Also, if the case is that you are also originating the serialization and it is from Java, you could use Java serialization altogether for a lower footprint and faster operation.
//producer side
FileOutputStream fos = new FileOutputStream(filename);
ObjectOutputStream oos = new ObjectOutputStream(new BufferedOutputStream(fos));
oos.writeObject(yourVeryComplexObjectStructure); //I am writing a list of ten 1MB objects
oos.flush();
oos.close();
fos.close();
//Consumer side
final FileInputStream fin = new FileInputStream(filename);
final ObjectInputStream ois = new ObjectInputStream(new BufferedInputStream(fin));
#SuppressWarnings("unchecked")
final YourVeryComplexObjectStructureType object = (YourVeryComplexObjectStructureType) ois.readObject();
ois.close();
fin.close();
Let's say I have a json that looks like this:
{"body":"abcdef","field":"fgh"}
Now suppose the value of the 'body' element is huge(~100 MB or more). I would like to stream out the value of the body element instead of storing it in a String.
How can I do this? Is there any Java library I could use for this?
This is the line of code that fails with an OutOfMemoryException when a large json value comes in:
String inputStreamString = (String) JsonPath.read(textValue.toString(), "$.body");
'textValue' here is a hadoop.io.Text object.
I'm assuming that the OutOfMemory error occurs because we try to do method calls like toString() (which creates a new object), and JsonPath.read(), all of which are done in-memory. I need to know if there is an approach I could take while handling large-sized textValue objects.
Please let me know if you need additional info.
JsonSurfer is good for processing very large JSON data with selective extraction.
Example how to surf in JSON data collecting matched values in the listeners:
BufferedReader reader = new BufferedReader(new FileReader(jsonFile));
JsonSurfer surfer = new JsonSurfer(GsonParser.INSTANCE, GsonProvider.INSTANCE);
SurfingConfiguration config = surfer.configBuilder().bind("$.store.book[*]", new JsonPathListener() {
#Override
public void onValue(Object value, ParsingContext context) throws Exception {
JsonObject book = (JsonObject) value;
}
}).build();
surfer.surf(reader, config);
Jackson offers a streaming API for generating and processing JSON data.
Am working with GWT application and integrated with Simple framework to parse objects into XML, I have POJO classes on client side and use the parser on server side. I need to write the serialized object to String variable instead of file cause files not allowed in GWT App engine https://groups.google.com/forum/?fromgroups=#!topic/google-web-toolkit/M7Zo3U7CKD8.
Current code I have in the server side on GWT RPC ServiceImpl
File result = new File("c:/myXMLFile.xml");
Serializer serializer = new Persister();
MyBeanToSerialize beanToSerialize = new MyBeanToSerialize("firstName","LastName");
serializer.write(beanToSerialize, result);
I found the solution for returning String from the XML parser by using the writer object instead of File the code is as the following:-
String parser(){
StringWriter writer = new StringWriter();
Serializer serializer = new Persister();
MyBeanToSerialize beanToSerialize = new MyBeanToSerialize("firstName","LastName");
serializer.write(beanToSerialize, writer);
return writer.getBuffer().toString();
)
I want convert json to xml
here is code
public class ConvertJSONtoXML {
public static void main(String[] args) throws Exception {
InputStream is = ConvertJSONtoXML.class.getResourceAsStream("demo1.txt");
String jsonData = IOUtils.toString(is);
XMLSerializer serializer = new XMLSerializer();
JSON json = JSONSerializer.toJSON(jsonData);
String xml = serializer.write((JSON) json);
System.out.println(xml);
Here is demo1.txt
{"name":"naveed" }
It reads demo1.txt file and convert into xml but i m trying to pass json as string.
String jsonString="{\"name\":\"naveed\" }";
InputStream is = ConvertJSONtoXML.class.getResourceAsStream(jsonString);
but it wont work for string..
i thing getResourceAsStream(jsonString) doesnt work for string....
please suggest any reference
The method getResourceAsStream() actually looks on the file system for resource identified by the input string and open an input stream for it.
You should rather use something like
InputStream is = new ByteArrayInputStream( jsonString.getBytes() );
Also, you should take care of using compatible charsets.
I'm starting to design an application, that will, in part, run through a directory of files and compare their extensions to their file headers.
Does anyone have any advice as to the best way to approach this? I know I could simply have a lookup table that will contain the file's header signature. e.g., JPEG: \xFF\xD8\xFF\xE0
I was hoping there might be a simper way.
Thanks in advance for your help.
I'm afraid it'll have to be more complicated than that. Not every file type has a header at all, and some (such as RAR) have their characteristic data structures at the end rather than at the beginning.
You may want to take a look at the Unix file command, which does the same job:
http://linux.die.net/man/1/file
http://linux.die.net/man/5/magic
If you don't need to do dirty work on these values (and you don't have linux) you could simply use an external program, like TrID, that is able to do this thing for you.
Maybe you can just work on its output without caring to doing it by yourself.. in anycase if you have just around 20 kinds of files that you will have to manage having a simple lookup table (eg. HashMap<String,byte[]>) is not that bad. Of cours this will work only if desidered file format has a magic number, otherwise you are on your own (or with an external program).
Because of the problem with the missing significant header for some file types (thanks #Michael) I would create a map of extension to a kind of type checker with a simple API like
public interface TypeCheck throws IOException {
public boolean isValid(InputStream data);
}
Now you can code something like
File toBeTested = ...;
Map<String,TypeCheck> typeCheckByExtension = ...;
TypeCheck check = typeCheckByExtension.get(getExtension(toBeTested.getName()));
if (check != null) {
InputStream in = new FileInputStream(toBeTested);
if (check.isValid(in)) {
// process valid file
} else {
// process invalid file
}
in.close();
} else {
// process unknown file
}
The Header check for JPEG for example may look like
public class JpegTypeCheck implements TypeCheck {
private static final byte[] HEADER = new byte[] {0xFF, 0xD8, 0xFF, 0xE0};
public boolean isValid(InputStream data) throws IOException {
byte[] header = new byte[4];
return data.read(header) == 4 && Arrays.equals(header, HEADER);
}
}
For other types with no significant header you can implement completly other type checks.
You can extract the mime type for each file and compare this to a map of mimetype/extension (Map<String, List<String>>, the first String is the mime type, the second is a list of valid extensions).
Resources :
Get the Mime Type from a File
JMimeMagic
On the same topic :
Java - HowTo extract MimeType from a byte[]
Getting A File's Mime Type In Java
You can know the file type of file reading the header using apache tika. Following code need apache tika jar.
InputStream is = MainApp.class.getResourceAsStream("/NetFx20SP1_x64.txt");
BufferedInputStream bis = new BufferedInputStream(is);
AutoDetectParser parser = new AutoDetectParser();
Detector detector = parser.getDetector();
Metadata md = new Metadata();
md.add(Metadata.RESOURCE_NAME_KEY,MainApp.class.getResource("/NetFx20SP1_x64.txt").getPath());
MediaType mediaType = detector.detect(bis, md);
System.out.println("MIMe Type of File : " + mediaType.toString());