DDevelopment & Design

Writing JAXB in Groovy

Suppose you want write a jaxb class in groovy. Why? Because you do not have to write these all getters, setters and other methods. You only have to write your fields down.@XmlRootElement@HashCodeAndEquals@ToStringclass Person { String firstName String …

Suppose you want write a jaxb class in groovy. Why? Because you do not have to write these all getters, setters and other methods. You only have to write your fields down.

@XmlRootElement 
@HashCodeAndEquals 
@ToString 
class Person {
    String firstName String lastName Integer age
}

 

Lets check if we could unmarshal xml to Person class:

def 'should unmarshall person xml to object'(){
    given:
        JAXBContext jc = JAXBContext.newInstance(Person)
        String xml = 'JohnSmith20' 
    expect:
        jc.createUnmarshaller().unmarshal(new StringReader(xml)) == new Person(firstName: 'John', lastName: 'Smith', age: 20)
}

 

When we try this, then we obtain an eception:

com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException: 1 counts of IllegalAnnotationExceptions
groovy.lang.MetaClass is an interface, and JAXB can't handle interfaces.
 this problem is related to the following location:
  at groovy.lang.MetaClass
  at public groovy.lang.MetaClass com.blogspot.przybyszd.jaxbingroovy.Person.getMetaClass()
  at com.blogspot.przybyszd.jaxbingroovy.Person

 at com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException$Builder.check(IllegalAnnotationsException.java:91)
 at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getTypeInfoSet(JAXBContextImpl.java:445)
 at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.(JAXBContextImpl.java:277)
 at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.(JAXBContextImpl.java:124)
 at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl$JAXBContextBuilder.build(JAXBContextImpl.java:1123)
 at com.sun.xml.internal.bind.v2.ContextFactory.createContext(ContextFactory.java:147)
 at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:247)
 at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:234)
 at javax.xml.bind.ContextFinder.find(ContextFinder.java:462)
 at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:641)
 at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:584)
 at com.blogspot.przybyszd.jaxbingroovy.PersonJaxbTest.should unmarshall person xml to object(PersonJaxbTest.groovy:10)

It is because groovy defines getMetaClass method for us. Marshaller and Unmarshaller use by default

XmlAccessType.PUBLIC_MEMBER what means that public getters and setters should be used during marshalling/unmarshalling. To solve this just add XmlAccessorType annotatnio with XmlAccessType.FIELD on jaxb class:

@XmlRootElement @EqualsAndHashCode @XmlAccessorType(XmlAccessType.FIELD) class Person {
    String firstName String lastName Integer age
}

 

Of course if you want to apply this rule for each jaxb class in package, then you could put XmlAccessorType in pacakge-info.java file.

@XmlAccessorType(XmlAccessType.FIELD) package com.blogspot.przybyszd.jaxbingroovy;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;

 

Great, it works. Now let’s check out marshaller:

def 'should marshall person'() {
    given:
        JAXBContext jc = JAXBContext.newInstance(Person)
        Person p = new Person(firstName: 'John', lastName: 'Smith', age: 20)
        StringWriter sw = new StringWriter()
    when:
        jc.createMarshaller().marshal(p, sw)
    then:
        String xml = sw.toString()
        GPathResult gPathResult = new XmlSlurper().parseText(xml)
        gPathResult.name() == 'person'
        gPathResult.firstName == 'John'
        gPathResult.lastName == 'Smith'
        gPathResult.age == '20'
}

 

And it also works. Source is available here.

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DDevelopment & Design

Need to make a quick json fixes – JSONPath for rescue

From time to time I have a need to do some fixes in my json data. In a world of flat files I do this with grep/sed/awk tool chain. How to handle it for JSON? Searching for a solution I came across the JSONPath. It quite mature tool (from 2007) but I haven't hear about it so I decided to share my experience with others.

First of all you can try it without pain online: http://jsonpath.curiousconcept.com/. Full syntax is described at http://goessner.net/articles/JsonPath/



But also you can download python binding and run it from command line:
$ sudo apt-get install python-jsonpath-rw
$ sudo apt-get install python-setuptools
$ sudo easy_install -U jsonpath

After that you can use inside python or with simple cli wrapper:
#!/usr/bin/python
import sys, json, jsonpath

path = sys.argv[1]

result = jsonpath.jsonpath(json.load(sys.stdin), path)
print json.dumps(result, indent=2)

… you can use it in your shell e.g. for json:
{
"store": {
"book": [
      {
"category": "reference",
"author": "Nigel Rees",
"title": "Sayings of the Century",
"price": 8.95
      },
      {
"category": "fiction",
"author": "Evelyn Waugh",
"title": "Sword of Honour",
"price": 12.99
      },
      {
"category": "fiction",
"author": "Herman Melville",
"title": "Moby Dick",
"isbn": "0-553-21311-3",
"price": 8.99
      },
      {
"category": "fiction",
"author": "J. R. R. Tolkien",
"title": "The Lord of the Rings",
"isbn": "0-395-19395-8",
"price": 22.99
      }
    ],
"bicycle": {
"color": "red",
"price": 19.95
    }
  }
}

You can print only book nodes with price lower than 10 by:
$ jsonpath '$..book[?(@.price

Result:
[
  {
"category": "reference",
"price": 8.95,
"title": "Sayings of the Century",
"author": "Nigel Rees"
  },
  {
"category": "fiction",
"price": 8.99,
"title": "Moby Dick",
"isbn": "0-553-21311-3",
"author": "Herman Melville"
  }
]

Have a nice JSON hacking!From time to time I have a need to do some fixes in my json data. In a world of flat files I do this with grep/sed/awk tool chain. How to handle it for JSON? Searching for a solution I came across the JSONPath. It quite mature tool (from 2007) but I haven't hear about it so I decided to share my experience with others.