Andres Almiray's Weblog

Yikes! been so busy at work that missed Json-lib's second anniversary by two days. Don't have exact download stats as sourceforge.net decided to give broken links for projects statistics for over a week now, last time I checked we were over the 78K mark

20 releases, 71 bug reports, 72 feature requests, 6 patches, 123 forum messages and countless direct emails we are still up and going strong. Thanks to everybody that has contributed to the project, and to the users too, we wouldn't be here if it wasn't because of you.

java json json-lib

Dear JRoller Community,
I'm pleased to announce that Json-lib version 2.2.2 has been released.

Download | Documentation | Faq | Changes

JSON-lib is a java library for transforming beans, maps and XML to JSON and back again to beans and DynaBeans. It is based on the work by Douglas Crockford in http://www.json.org/java.

Changelog:

announcement java json json-lib release

I just discovered by accident that Json-lib was mentioned during JavaOne 2008 at BOF-5361 The Long Tail Treasure Trove (look for project #14 of 30). Considering that heavy hitters as ASM, CGLib, Selenium and XOM are also in the list, all I can say is wow! Thanks Brian and Gianugo!

I would have been there if it wasn't because I had a BOF of my own at the same time slot.

java javaone javaone2008 json json-lib

Another year has come and go writing this blog. An interesting shift in the content can be noticed as I wrote more and more about Groovy than Java (wait, isn't Groovy Java too? ), I hope I haven't bored my readership (albeit small) to tears with my Groovy ramblings. Following the spirit of last year's anniversary post, here are the 12 most viewed entries on this blog (ah, the memories) And the three runner ups of this year are: Looks like I was quite active during summer and winter...

groovy java json

Last week I received a rather interesting message from a GWT user, asking if it was possible to return a top level JSONArray from JSONView instead of a top level JSONObject, because it seems that in some cases GWT expects the data to be contained in an array and not an object. I thought that adding a flag would be enough, but maven's transitive dependency management (I have a strong love/hate relationship with maven, more love than hate) complicated things a little bit, hence the recent JsTester release.

The good news is that all problems are solved now and the flag has been added, just remember to call setForceTopLevelArray on the view before you render the JSON output and you are in business. You may download the jar file from Json-lib's download page.

Feedback is always appreciated.

java json json-lib spring

One of the driving goals of Json-lib since the very beginning has been simplifying Java-to-JSON conversions, no matter how complex the data may be. Many users have reported that they are developing applications that expose hibernated domains, but due to Hibernate using CGLib to do its magic there were some unexpected gotchas, which prompted some tweaks into Json-lib. The following is a list of tips and hints that may come in handy when using both libraries.

The first gotcha is that hibernated objects are really proxies, and as such they expose more properties than the ones you wrote, so let's make sure Json-lib only serializes those properties you are interested in. This task may be accomplished in 4 different ways, depending on your needs

1. Implementing JSONString is the most invasive option as it ties your code to Json-lib's APIs (don't worry it won't go away) and gives you full responsibility on how the class should be represented in a valid JSON string. Here is an example of how it may look:

public class Person implements JSONString { private String name; private String lastname; private Address address; // getters & setters public String toJSONString() { return "{name:'"+name+"',lastname:'"+lastname+"'}"; } }

2. The next option allows a higher level of configuration as you can add/update properties to be excluded at will by registering a String array with JsonConfig

public class Person { private String name; private String lastname; private Address address; // getters & setters } JsonConfig jsonConfig = new JsonConfig(); jsonConfig.setExclusions( new String[]{ "address" } ); Person bean = /* initialize */; JSON json = JSONSerializer.toJSON( bean, jsonConfig );

Be aware that this option does not discriminate the source of the properties, which means that if you have 2 beans with an address property, that property will be omitted in both cases, this "inconvenience" leads to the netx option.

3. Use a PropertyFilter, allowing you a finer detail on both the source and properties to be excluded. You must pay attention on how you register a PropertyFilter as the same mechanism is used when transforming from JSON to Java.

public class Person { private String name; private String lastname; private Address address; // getters & setters } JsonConfig jsonConfig = new JsonConfig(); jsonConfig.setJsonPropertyFilter( new PropertyFilter(){ public boolean apply( Object source, String name, Object value ){ // return true to skip name return source instanceof Person && name.equals("address"); } }); Person bean = /* initialize */; JSON json = JSONSerializer.toJSON( bean, jsonConfig );

4. Lastly you may use a JsonBeanProcessor, which works like JSONString in the sense that it must return a valid JSONObject that represents the whole bean but it is not as invasive.

public class Person { private String name; private String lastname; private Address address; // getters & setters } JsonConfig jsonConfig = new JsonConfig(); jsonConfig.registerJsonBeanProcessor( Person.class, new JsonBeanProcessor(){ public JSONObject processBean( Object bean, JsonConfig jsonConfig ){ if( !(bean instanceof Person) ){ return new JSONObject(true); } Person person = (Person) bean; return new JSONObject() .element( "name", person.getName() ) .element( "lastname", person.getLastname() ); } }); Person bean = /* initialize */; JSON json = JSONSerializer.toJSON( bean, jsonConfig );

And it is here with JsonBeanProcessors where we encounter the second gotcha related to CGlib. As you noticed we registered the processor using Person as target class, but Hibernate returns a Proxy that is not exactly a Person but a subclass (if possible) of Person. The default matching algorithm used by Json-lib will try to match the exact class (using equals), meaning that your processor will not be called when you expect it to be,this is why JsonBeanProcessorMatcher was introduced, now you are be able to write the following code

public class Person { private String name; private String lastname; private Address address; // getters & setters } JsonConfig jsonConfig = new JsonConfig(); jsonConfig.registerJsonBeanProcessor( Person.class, new JsonBeanProcessor(){ public JSONObject processBean( Object bean, JsonConfig jsonConfig ){ if( !(bean instanceof Person) ){ return new JSONObject(true); } Person person = (Person) bean; return new JSONObject() .element( "name", person.getName() ) .element( "lastname", person.getLastname() ); } }); jsonConfig.registerJsonBeanProcessorMatcher( new JsonBeanProcessorMatcher(){ public Object getMatch( Class target, Set/* */ matches ){ for( Object match : matches ){ if( ((Class)match).isAssignableFrom(target) ){ return match; } } return null; } }); Person bean = /* initialize */; JSON json = JSONSerializer.toJSON( bean, jsonConfig );

I hope these examples help dispel some doubts, in any case please feel free to drop by Json-lib's forum and mailing lists.

java json json-lib

It's been a while since I blogged about Json-lib so here goes what has happened since last time. One of the most sought features for 2.2.1 (besides generics) was handling XML -> JSON conversion as expected when encountering a "top level" object that happened to have 1 single child. Problem is that that XML is also a valid top level array, so an artificial way to differentiate both cases had to be implemented, thanks to a simple flag the job was done, or was it? turns out the feature was not completely done, but I'm happy to say that now it finally is (thanks to some users pointing out a missing corner case).

Json-lib supports both Groovy and JRuby for quite a while, perhaps you saw in the news that JRuby 1.1 was released a couple of weeks ago, well Groovy 1.5.5 was released today, that prompt me to download both versions and upgrade Json-lib's dependencies along the way. Speaking of Groovy, previously to version 2.2.1 Json-lib would automatically enhance classes to use the as keyword to perform type conversions, but as Kohsuke noted, it broke Hudson in unexpected ways (MetaClass magic gone bad) so from that release onward it no longer enhances classes unless you tell it so, which by the way is quite easy

GJson.enhanceClasses() def json = "{name:'Duke'}" as JSON

There have been other issues that have been solved as well but I think these are the more relevant to mention for now, as I'm still looking for a way to add generics to the library.

features java json json-lib

Dear JRoller Community,
I'm pleased to announce that Json-lib version 2.2.1 has been released.

Download | Documentation | Faq | Changes

JSON-lib is a java library for transforming beans, maps and XML to JSON and back again to beans and DynaBeans. It is based on the work by Douglas Crockford in http://www.json.org/java.

Changelog: This release upgrades to Groovy 1.5.4 and removes autoregistering custom metaClasses for String, List and Map.

announcement java json json-lib release

According to Sourceforge's stats Json-lib reached the 50k download mark today, hurray! this measure doesn't take into account downloads from maven's central repo though, so the real download mark should be above that number.

Thanks to everybody that have come forward with suggestions, bug reports and questions, you all helped in making Json-lib a better project. Stay tunned for more Json-lib news.

json json-lib

It's been a long while since I posted about JsonView (more than a year and a half ago), recently I received a couple of messages from users that would like to have it updated, because things at SPR-2010 look a little bleak I decided to release it as an extension of Json-lib (something I should have done since the beginning I think). The package is available here.

announcement json json-lib release spring

Among the new features available in Json-lib 2.2 you'll fine a new page on the projects' site showing quick examples of how to use the library.

The page was long overdue since 2.0 as by that time the library already had enough options, but with filters, processors, strategies, Groovy and JRuby support it now has become the most complete JSON parsing library (its only possible thanks to users' suggestions), thus making it little bit difficult to keep track on how to configure all the options.

the information displayed on the page is in no way complete and will be constantly updated with examples of the most recent features and with new ones as they are added.

Speaking of which, generics support was at some point introduced into 2.2-SNAPSHOT thanks to Matt Small, and his employer Wavemaker, but was left out due to some backport problems with jdk5/jdk3 versions (I really wish to let go of the jdk3 version), I'll be targeting 2.3 to be full generics compliant.

If you have a code example suggestion please feel free to drop by the user list or the project's forum at https://sourceforge.net/projects/json-lib.

Feedback is always appreciated.

json json-lib

Dear JRoller Community,
I'm pleased to announce that Json-lib version 2.2 has been released.

Download | Documentation | Faq | Changes

JSON-lib is a java library for transforming beans, maps and XML to JSON and back again to beans and DynaBeans. It is based on the work by Douglas Crockford in http://www.json.org/java.

Changelog: Fixes

java json json-lib release

I was browsing through Json-lib's user list and issue tracker to see if there was a show-stopper for the next release (coming soon!) and lo and behold, some users would like to see XPath-like expressions in the library.

Being a Groovy fan myself I know its a matter of switching to hip-language-with-the-cool-name, use GPath and get on with life. Alas not everybody can switch languages so the question remains, how to enable XPath-like expressions in JSON while using Java.

Seems like Stefan Gössner had the same need and created JSONPath. It looks nice at first but my main gripe with that project is that even though it lets you access JSON with XPath constructs, they are not the same XPath constructs you may already use today with XML, meaning you'll have to learn a mini-language to understand those expressions (and no Java version yet).

I needed another solution, so I started thinking that I would have to cook my own XPath-for-JSON thing when a quick google search reminded me that JXPath existed, what a time saver! I did some quick tests with simple and nested expressions and all of them passed, with zero (that's right, zero!) lines of code to get it working, turns out JXPath is Map friendly, so is Json-lib.

JXPath is only one of the many projects available at the Apache Commons umbrella project, and I'm glad that those projects are still with us (some would say commons-collections, commons-lang or commons-beanutils are useless or half useless since Java5, I disagree). So the next time you feel like "reinventing the wheel" in Java take a look a Apache Commons, chances are you may find something that already provides what you need.

apache commons java json json-lib xpath

Its just been a couple of days after Json-lib 2.1 was released and feature requests are already pouring in. The first one ask for custom handling of default values when a null reference is encountered. Per the JSON spec if a value is null Json-lib applies the following rules But what if you would like to return 'null' if an Integer reference is null? (yes I know that would against the spec), or if a MyCoolBean reference is null you'd like to return '{ empty: true }' instead of simply 'null'? that's the reason why DefaultValueProcessor is now available, along with DefaultValueProcessorMatcher (for the same reasons shown here).

The second feature caught me by surprise as I didn't understand the usefulness of it at first sight, the thing is that a user has a bean which uses a composed Map for its property representation, but that bean does not implements Map nor it is a DynaBean, so he would like to call internalMap.put() instead of going to trough the usual PropertyUtils.setProperty(), which depending on the client code can be sometimes a performance bottleneck. After a quick message exchange and a prompt patch PropertySetStrategy is ready.

These features have a default implementation already plugged into JsonConfig, which is the place where you would also plug-in your custom implementations.

The third one is related to JSON <-> serialization. As you may probably know, XMLSerializer will output type hints (unless configured otherwise) to an XML string, using those hints again when transforming back to JSON. The hints use reserved keywords as attributes [type,class,params,null] but it may be the case for some users that some of those keywords must have business meaning instead of just 'framework' meaning, how do we cope with that? by adding a 'json_' prefix to the reserved keywords. In order to maintain backward compatibility there is a flag on XMLSerializer (typeHintsCompatibility) that when set to false will enable the prefix, when true it will disregard it.

The code is already on the cvs along with a couple of quick bug fixes. Keep posted for more Json-lib updates.

features json json-lib xml

Dear JRoller Community,
I'm pleased to announce that Json-lib version 2.1 has been released.

Download | Documentation | Faq | Changes

JSON-lib is a java library for transforming beans, maps and XML to JSON and back again to beans and DynaBeans. It is based on the work by Douglas Crockford in http://www.json.org/java.

Changelog: Remember that you can also configure json-lib's maven2 repo at http://json-lib.sourceforge.net/m2/repo/release.

features json json-lib release