components/camel-xmljson/src/main/docs/xmljson-dataformat.adoc

## XML JSon DataFormat

*Available as of Camel version 2.10*

Camel already supports a number of data formats to perform XML and
JSON-related conversions, but all of them require a POJO either as an
input (for marshalling) or produce a POJO as output (for unmarshalling).
This data format provides the capability to convert from XML to JSON and
vice-versa directly, without stepping through intermediate POJOs.

This data format leverages the
http://json-lib.sourceforge.net/[Json-lib] library to achieve direct
conversion. In this context, XML is considered the high-level format,
while JSON is the low-level format. Hence, the marshal/unmarshal
semantics are assigned as follows:

* marshalling => converting from XML to JSON
* unmarshalling => converting from JSON to XML.

### Options

// dataformat options: START
The XML JSon dataformat supports 13 options which are listed below.



[width="100%",cols="2s,1m,1m,6",options="header"]
|=======================================================================
| Name | Default | Java Type | Description
| encoding |  | String | Sets the encoding. Used for unmarshalling (JSON to XML conversion).
| elementName |  | String | Specifies the name of the XML elements representing each array element. Used for unmarshalling (JSON to XML conversion).
| arrayName |  | String | Specifies the name of the top-level XML element. Used for unmarshalling (JSON to XML conversion). For example when converting 1 2 3 it will be output by default as 123. By setting this option or rootName you can alter the name of element 'a'.
| forceTopLevelObject | false | Boolean | Determines whether the resulting JSON will start off with a top-most element whose name matches the XML root element. Used for marshalling (XML to JSon conversion). If disabled XML string 12 turns into 'x: '1' 'y': '2' . Otherwise it turns into 'a': 'x: '1' 'y': '2' .
| namespaceLenient | false | Boolean | Flag to be tolerant to incomplete namespace prefixes. Used for unmarshalling (JSON to XML conversion). In most cases json-lib automatically changes this flag at runtime to match the processing.
| rootName |  | String | Specifies the name of the top-level element. Used for unmarshalling (JSON to XML conversion). If not set json-lib will use arrayName or objectName (default value: 'o' at the current time it is not configurable in this data format). If set to 'root' the JSON string 'x': 'value1' 'y' : 'value2' would turn into value1value2 otherwise the 'root' element would be named 'o'.
| skipWhitespace | false | Boolean | Determines whether white spaces between XML elements will be regarded as text values or disregarded. Used for marshalling (XML to JSon conversion).
| trimSpaces | false | Boolean | Determines whether leading and trailing white spaces will be omitted from String values. Used for marshalling (XML to JSon conversion).
| skipNamespaces | false | Boolean | Signals whether namespaces should be ignored. By default they will be added to the JSON output using xmlns elements. Used for marshalling (XML to JSon conversion).
| removeNamespacePrefixes | false | Boolean | Removes the namespace prefixes from XML qualified elements so that the resulting JSON string does not contain them. Used for marshalling (XML to JSon conversion).
| expandableProperties |  | List | With expandable properties JSON array elements are converted to XML as a sequence of repetitive XML elements with the local name equal to the JSON key for example: number: 123 normally converted to: 123 (where e can be modified by setting elementName) would instead translate to 123 if number is set as an expandable property Used for unmarshalling (JSON to XML conversion).
| typeHints |  | String | Adds type hints to the resulting XML to aid conversion back to JSON. Used for unmarshalling (JSON to XML conversion).
| contentTypeHeader | false | Boolean | Whether the data format should set the Content-Type header with the type from the data format if the data format is capable of doing so. For example application/xml for data formats marshalling to XML or application/json for data formats marshalling to JSon etc.
|=======================================================================
// dataformat options: END

### Basic Usage with Java DSL

#### Explicitly instantiating the data format

Just instantiate the `XmlJsonDataFormat` from package
`org.apache.camel.dataformat.xmljson`. Make sure you have installed the
`camel-xmljson` feature (if running on OSGi) or that you've included
`camel-xmljson-{version}.jar` and its transitive dependencies in your
classpath. Example initialization with a default configuration:

[source,java]
----
XmlJsonDataFormat xmlJsonFormat = new XmlJsonDataFormat();
----

To tune the behaviour of the data format as per the options above, use
the appropriate setters:

[source,java]
----
XmlJsonDataFormat xmlJsonFormat = new XmlJsonDataFormat();
xmlJsonFormat.setEncoding("UTF-8");
xmlJsonFormat.setForceTopLevelObject(true);
xmlJsonFormat.setTrimSpaces(true);
xmlJsonFormat.setRootName("newRoot");
xmlJsonFormat.setSkipNamespaces(true);
xmlJsonFormat.setRemoveNamespacePrefixes(true);
xmlJsonFormat.setExpandableProperties(Arrays.asList("d", "e"));
----

Once you've instantiated the data format, the next step is to actually
use the it from within the `marshal()` and `unmarshal()` DSL elements:

[source,java]
----
// from XML to JSON
from("direct:marshal").marshal(xmlJsonFormat).to("mock:json");
// from JSON to XML
from("direct:unmarshal").unmarshal(xmlJsonFormat).to("mock:xml");
----

#### Defining the data format in-line

Alternatively, you can define the data format inline by using the
`xmljson()` DSL element:

[source,java]
----
// from XML to JSON - inline dataformat
from("direct:marshalInline").marshal().xmljson().to("mock:jsonInline");
// from JSON to XML - inline dataformat
from("direct:unmarshalInline").unmarshal().xmljson().to("mock:xmlInline");
----

If you wish, you can even pass in a `Map<String, String>` to the inline
methods to provide custom options:

[source,java]
----
Map<String, String> xmlJsonOptions = new HashMap<String, String>();
xmlJsonOptions.put(org.apache.camel.model.dataformat.XmlJsonDataFormat.ENCODING, "UTF-8");
xmlJsonOptions.put(org.apache.camel.model.dataformat.XmlJsonDataFormat.ROOT_NAME, "newRoot");
xmlJsonOptions.put(org.apache.camel.model.dataformat.XmlJsonDataFormat.SKIP_NAMESPACES, "true");
xmlJsonOptions.put(org.apache.camel.model.dataformat.XmlJsonDataFormat.REMOVE_NAMESPACE_PREFIXES, "true");
xmlJsonOptions.put(org.apache.camel.model.dataformat.XmlJsonDataFormat.EXPANDABLE_PROPERTIES, "d e");

// from XML to JSON - inline dataformat w/ options
from("direct:marshalInlineOptions").marshal().xmljson(xmlJsonOptions).to("mock:jsonInlineOptions");
// form JSON to XML - inline dataformat w/ options
from("direct:unmarshalInlineOptions").unmarshal().xmljson(xmlJsonOptions).to("mock:xmlInlineOptions");
----

### Basic usage with Spring or Blueprint DSL

Within the `<dataFormats>` block, simply configure an `xmljson` element
with unique IDs:

[source,xml]
----
<dataFormats>
    <xmljson id="xmljson"/>
    <xmljson id="xmljsonWithOptions" forceTopLevelObject="true" trimSpaces="true" rootName="newRoot" skipNamespaces="true"
             removeNamespacePrefixes="true" expandableProperties="d e"/>
</dataFormats>
----

Then you simply refer to the data format object within your
`<marshal />` and `<unmarshal />` DSLs:

[source,xml]
----
<route>
    <from uri="direct:marshal"/>
    <marshal ref="xmljson"/>
    <to uri="mock:json" />
</route>

<route>
    <from uri="direct:unmarshalWithOptions"/>
    <unmarshal ref="xmljsonWithOptions"/>
    <to uri="mock:xmlWithOptions"/>
</route>
----

Enabling XML DSL autocompletion for this component is easy: just refer
to the appropriate http://camel.apache.org/xml-reference.html[Schema
locations], depending on whether you're using
http://camel.apache.org/schema/spring/[Spring] or
http://camel.apache.org/schema/blueprint/[Blueprint] DSL. Remember that
this data format is available from Camel 2.10 onwards, so only schemas
from that version onwards will include these new XML elements and
attributes.

The syntax with link:using-osgi-blueprint-with-camel.html[Blueprint] is
identical to that of the Spring DSL. Just ensure the correct namespaces
and schemaLocations are in use.

### Namespace mappings

XML has namespaces to fully qualify elements and attributes; JSON
doesn't. You need to take this into account when performing XML-JSON
conversions.

To bridge the gap, http://json-lib.sourceforge.net/[Json-lib] has an
option to bind namespace declarations in the form of prefixes and
namespace URIs to XML output elements while unmarshalling (i.e.
converting from JSON to XML). For example, provided the following JSON
string:

[source,json]
----
{ "pref1:a": "value1", "pref2:b": "value2" }
----

you can ask Json-lib to output namespace declarations on elements
`pref1:a` and `pref2:b` to bind the prefixes `pref1` and `pref2` to
specific namespace URIs.

To use this feature, simply create
`XmlJsonDataFormat.NamespacesPerElementMapping` objects and add them to
the `namespaceMappings` option (which is a `List`).

The `XmlJsonDataFormat.NamespacesPerElementMapping` holds an element
name and a Map of [prefix => namespace URI]. To facilitate mapping
multiple prefixes and namespace URIs, the
`NamespacesPerElementMapping(String element, String pipeSeparatedMappings)`
constructor takes a String-based pipe-separated sequence of [prefix,
namespaceURI] pairs in the following way:
`|ns2|http://camel.apache.org/personalData|ns3|http://camel.apache.org/personalData2|`.

In order to define a default namespace, just leave the corresponding key
field empty:
`|ns1|http://camel.apache.org/test1||http://camel.apache.org/default|`.

Binding namespace declarations to an element name = empty string will
attach those namespaces to the root element.

The full code would look like that:

[source,java]
----
XmlJsonDataFormat namespacesFormat = new XmlJsonDataFormat();
List<XmlJsonDataFormat.NamespacesPerElementMapping> namespaces = new ArrayList<XmlJsonDataFormat.NamespacesPerElementMapping>();
namespaces.add(new XmlJsonDataFormat.
                       NamespacesPerElementMapping("", "|ns1|http://camel.apache.org/test1||http://camel.apache.org/default|"));
namespaces.add(new XmlJsonDataFormat.
                       NamespacesPerElementMapping("surname", "|ns2|http://camel.apache.org/personalData|" +
                           "ns3|http://camel.apache.org/personalData2|"));
namespacesFormat.setNamespaceMappings(namespaces);
namespacesFormat.setRootElement("person");
----

And you can achieve the same in Spring DSL.

#### Example

Using the namespace bindings in the Java snippet above on the following
JSON string:

[source,json]
----
{ "name": "Raul", "surname": "Kripalani", "f": true, "g": null}
----

 

Would yield the following XML:

[source,xml]
----
<person xmlns="http://camel.apache.org/default" xmlns:ns1="http://camel.apache.org/test1">
    <f>true</f>
    <g null="true"/>
    <name>Raul</name>
    <surname xmlns:ns2="http://camel.apache.org/personalData" xmlns:ns3="http://camel.apache.org/personalData2">Kripalani</surname>
</person>
----

Remember that the JSON spec defines a JSON object as follows:

_________________________________________________________
An object is an unordered set of name/value pairs. [...].
_________________________________________________________

That's why the elements are in a different order in the output XML.

### Dependencies

To use the link:xmljson.html[XmlJson] dataformat in your camel routes
you need to add the following dependency to your pom:

[source,xml]
----
<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-xmljson</artifactId>
  <version>x.x.x</version>
  <!-- Use the same version as camel-core, but remember that this component is only available from 2.10 onwards -->
</dependency>

<!-- And also XOM must be included. XOM cannot be included by default due to an incompatible
license with ASF; so add this manually -->
<dependency>
  <groupId>xom</groupId>
  <artifactId>xom</artifactId>
  <version>1.2.5</version>
</dependency>
----

### See Also

* link:data-format.html[Data Format]
* http://json-lib.sourceforge.net/[json-lib]