Hello,

Since Nuxeo 5.6 (the nuxeo-automation-client you chose is a 5.6 date-based version, aka a milestone waiting for 5.6 release), json-lib is being replaced with jackson.

When you want some information about the third-party libraries' versions used/recommended in Nuxeo, you should look at our corporate POM org.nuxeo:nuxeo-ecm. Here is dependency information about json-lib and jackson:

<!-- deprecated - use jackson instead -->
<dependency>
  <groupId>net.sf.json-lib</groupId>
  <artifactId>json-lib</artifactId>
  <version>2.4</version>
  <classifier>jdk15</classifier>
</dependency>
<dependency>
  <groupId>org.codehaus.jackson</groupId>
  <artifactId>jackson-core-asl</artifactId>
  <version>1.8.1</version>
</dependency>
<dependency>
  <groupId>org.codehaus.jackson</groupId>
  <artifactId>jackson-mapper-asl</artifactId>
  <version>1.8.1</version>
</dependency>

When you encounter a java.lang.ClassNotFoundException (or java.lang.NoClassDefFoundError), first look into our Maven repository for the artifacts providing the wanted class, then find in our corporate POM which artifact matches the previous list.

Note if your project is built with Maven, you can automatically retrieve the dependencyManagement from the Nuxeo corporate POM version corresponding to the automation client you use (or any POM inheriting from org.nuxeo:nuxeo-ecm such as org.nuxeo:nuxeo-addons-parent or org.nuxeo.ecm.distribution:nuxeo-distribution). For instance, in your case, you would set the following in your project POM:

<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>org.nuxeo.ecm.distribution</groupId>
      <artifactId>nuxeo-distribution</artifactId>
      <version>5.6-I20120428_0115</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
  </dependencies>
</dependencyManagement>
<dependencies>
  <dependency>
    <groupId>org.nuxeo.ecm.automation</groupId>
    <artifactId>nuxeo-automation-client</artifactId>
  </dependency>
  <dependency>
    <groupId>org.codehaus.jackson</groupId>
    <artifactId>jackson-core-asl</artifactId>
  </dependency>
  <dependency>
    <groupId>org.codehaus.jackson</groupId>
    <artifactId>jackson-mapper-asl</artifactId>
  </dependency>
  <dependency>
    <groupId>net.sf.ezmorph</groupId>
    <artifactId>ezmorph</artifactId>
  </dependency>
  <dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
  </dependency>
  <dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpcore</artifactId>
  </dependency>
  <dependency>
    <groupId>javax.mail</groupId>
    <artifactId>mail</artifactId>
  </dependency>
</dependencies>

That way, you don't have to worry about versions and you can easily upgrade Nuxeo.