Develop Reference

Generate and parse text files in Java

I'm looking for a library/framework to generate/parse TXT files from/into Java objects.
I'm thinking in something like Castor or JAXB, where the mapping between the file and the objects can be defined programmatically or with XML/annotations. The TXT file is not homogeneous and has no separators (fixed positions). The size of the file is not big, therefore DOM-like handling is allowed, no streaming required.
For instance:
TextWriter.write(Collection objects) -> FileOutputStream
TextReader.read(FileInputStream fis) -> Collection

I suggest you use google's protocol buffers
Protocol buffers are a flexible, efficient, automated mechanism for
serializing structured data – think XML, but smaller, faster, and
simpler. You define how you want your data to be structured once, then
you can use special generated source code to easily write and read
your structured data to and from a variety of data streams and using a
variety of languages. You can even update your data structure without
breaking deployed programs that are compiled against the "old" format.
Protobuf messages can be exported/read in binary or text format.
Other solutions would depend on what you call text file : if base64 is texty enough for you, you could simply use java standard serialization with base64 encoding of the binary stream.

You can do this using Jackson serialize to JSON and back
http://jackson.codehaus.org/

Just generate and parse it with XML or JSON formats, there's a whole load of libraries out there that will do all the work for you.

Ruby object to Java object

I want to create an object from a Ruby program and store it in an SQL database as a blob. I then want to be able to read this blob directly into a Java program at a later date. I understand that these blobs will probably be incompatible. How can I go about making a Java-readable blob from Ruby?

You can use json (xml, yaml) format to store object as string. And parse it in java.

Serialize ruby object to YAML (or JSON, XML etc)
Save it in the DB
Deserialize it from YAML to Java object

You should use thrift, it is much faster than (de)serializing json. See the benchmark here

Send ArrayList over the network - Convert Java ArrayList to XML String

I'm new to Java. I want to send an array (ArrayList) of objects over the network via Java Web Service to my Silverlight app. This ArrayList contains custom class objects:
ArrayList<SVNSearchResult> results
so I'm thinking the best way is to serialize this to an XML String and on the Silverlight part, use LinQ to parse it. If there's a better way to send it please let me know. Thanks.

XML is a good fit for this. JSON would be one of the other usual suspects these days.
Whatever format you end up choosing, make sure you get the encoding right.

For a starter, try JSON. It has a network-efficient format, and is supported by any major language in the world.
XML is only my second choice as it is more complicated to generate/parse and is more verbose.

How to deserialize in PHP an object serialized in Java

Is there any way to deserialize in PHP an object serialized in Java? IE If I have a Java class that implements Serialization and I use an ObjectOutputStream to write the object, and convert the result to a string, is there a way in PHP to take that string and create a similar object representation from it?
What does the Java Serialized data look like?
Response:
���sr�com.site.entity.SessionV3Data���������xpsr�java.util.HashMap���`��F�
loadFactorI� thresholdxp?#�����w������t� sessionIdt�0NmViMzUxYWItZDRmZC00MWY4LWFlMmUtZjg2YmZjZGUxNjg5xx
:)

I would heavily recommend you don't do this. Java serialization is meant for a Java instance to both save and load the data (for either transmission to another Java application or persistence between invocations of the same application). It was not at all meant to be a cross-platform protocol.
I would advise you to make an API adapter layer between the two. Output the contents of your Java object to a format you can work with in PHP, be it XML, YAML, or even a binary format (where you could use DataOutputStream).

What is the easiest way to eat soup with chopsticks when the soup was put in a bowl with a ladle? Put the soup in a cup and discard your chopsticks, because chopsticks are a poor choice for aiding in the consumption of soup. A cup (ubiquitous) eliminates external dependencies except for "mouth" and "opposable thumbs", both of which come with the standard library of humans.
A more elegant solution would be to encode that Java object with a JSON Serializer or XML serializer. Protocol Buffers or any other intentionally cross-language serialization technique would work fine plus Protocol Buffers can efficiently encode binary data.

Some time ago i did something simillar. However i didn't make PHP read "Java serialize" format. I did the oposite, that is, made Java serialize itself to a "PHP serialize" format. This is actually quite easy. Have look at PHPSerializedResponseWriter class that is a part of Solr package:
https://github.com/terrancesnyder/solr-analytics/blob/master/solr/core/src/java/org/apache/solr/response/PHPSerializedResponseWriter.java
...then all you have to do is just read the string and call:
$result = unserialize($string);

From comments in the online PHP manual, there is a Java class that serializes to the PHP serialization format that you can look into. Then you can unserialize the data using the standard PHP functionality.

Is it possible to use one of the more common cross platform data formats like JSON to communicate between your Java app and PHP? PHP has plenty of parsers for those formats. Check out json_decode for an example.

Is there any way to deserialize in PHP
an object serialized in Java?
Yes. The question is, should you? Exporting the Java object as XML or JSON probably makes more sense.
The following SO question might also help.
Dynamically create PHP object based on string

understanding json

JSON stands for JavaScript Object Notation. But how come languages like php, java, c etc can also communication each other with json.
What I want to know is that, am i correct to say that json is not limited to js only, but served as a protocol for applications to communicate with each other over the network, which is the same purpose as XML?

JSON cannot handle complex data hierarchies like XML can (attributes, namespaces, etc.), but on the other hand you don't get the same overhead with JSON as you get with XML (if you don't need the complex data structures).
Since JSON is plain text with a special notation for JS to interpret, it's an easy protocol to adopt in other languages.

It is easy for a JS script to parse JSON, since it can be done using 'eval' in which the JS enginge can use its full power.
On the other hand, it is more complicated to generate JSON from within JS. Usually one uses the JSON package from www.json.org in which an object can easily be serialised using JSON.stringify, but it is implemented in JS so its not running with optimal performance.
So serialising JSON is about the same complexity using JS as when using Java, PHP or any other server side language.
Therefore, in my opinion, JSON is best suited when there is asymmetry between produce/consumer e.g. a web server that generates a lot of data that is consumed by the web application. Not the other way around.
But! When one choses JSON as data format it should be used in both directions, not XML<>JSON. Except for when simple get requests are used to retrieve JSON data.

yes, JSON is also wildly used as a data exchange protocol much like XML.
Typically a program (not written in JavaScript) needs a JSON library to parse and create JSON objects (although you can probably create them even without one).

Your right - it's a light weight data interchange format -- more details at: http://www.json.org

You are completely correct. JSON definition of how data should be formatted. It is more light weight than XML and therefore well suited to things like AJAX where you want to send data back and forth to the server quickly.