XStream DataFormat

Available as of Camel version 1.3

XStream is a Data Format which uses the XStream library to marshal and unmarshal Java objects to and from XML.

To use XStream in your camel routes you need to add the a dependency on camel-xstream which implements this data format.

Maven users will need to add the following dependency to their pom.xml for this component:

<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-xstream</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>

Options

The XStream dataformat supports 10 options, which are listed below.

Name Default Java Type Description

permissions

String

Adds permissions that controls which Java packages and classes XStream is allowed to use during unmarshal from xml/json to Java beans. A permission must be configured either here or globally using a JVM system property. The permission can be specified in a syntax where a plus sign is allow, and minus sign is deny. Wildcards is supported by using . as prefix. For example to allow com.foo and all subpackages then specfy com.foo.. Multiple permissions can be configured separated by comma, such as com.foo.,-com.foo.bar.MySecretBean. The following default permission is always included: -,java.lang.,java.util. unless its overridden by specifying a JVM system property with they key org.apache.camel.xstream.permissions.

encoding

String

Sets the encoding to use

driver

String

To use a custom XStream driver. The instance must be of type com.thoughtworks.xstream.io.HierarchicalStreamDriver

driverRef

String

To refer to a custom XStream driver to lookup in the registry. The instance must be of type com.thoughtworks.xstream.io.HierarchicalStreamDriver

mode

String

Mode for dealing with duplicate references The possible values are: NO_REFERENCES ID_REFERENCES XPATH_RELATIVE_REFERENCES XPATH_ABSOLUTE_REFERENCES SINGLE_NODE_XPATH_RELATIVE_REFERENCES SINGLE_NODE_XPATH_ABSOLUTE_REFERENCES

converters

List

List of class names for using custom XStream converters. The classes must be of type com.thoughtworks.xstream.converters.Converter

aliases

Map

Alias a Class to a shorter name to be used in XML elements.

omitFields

Map

Prevents a field from being serialized. To omit a field you must always provide the declaring type and not necessarily the type that is converted.

implicitCollections

Map

Adds a default implicit collection which is used for any unmapped XML tag.

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.

Spring Boot Auto-Configuration

When using Spring Boot make sure to use the following Maven dependency to have support for auto configuration:

<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-xstream-starter</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>

The component supports 30 options, which are listed below.

Name Description Default Type

camel.dataformat.json-xstream.allow-jms-type

Used for JMS users to allow the JMSType header from the JMS spec to specify a FQN classname to use to unmarshal to.

false

Boolean

camel.dataformat.json-xstream.allow-unmarshall-type

If enabled then Jackson is allowed to attempt to use the CamelJacksonUnmarshalType header during the unmarshalling. This should only be enabled when desired to be used.

false

Boolean

camel.dataformat.json-xstream.collection-type-name

Refers to a custom collection type to lookup in the registry to use. This option should rarely be used, but allows to use different collection types than java.util.Collection based as default.

String

camel.dataformat.json-xstream.content-type-header

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.

false

Boolean

camel.dataformat.json-xstream.disable-features

Set of features to disable on the Jackson com.fasterxml.jackson.databind.ObjectMapper. The features should be a name that matches a enum from com.fasterxml.jackson.databind.SerializationFeature, com.fasterxml.jackson.databind.DeserializationFeature, or com.fasterxml.jackson.databind.MapperFeature Multiple features can be separated by comma

String

camel.dataformat.json-xstream.enable-features

Set of features to enable on the Jackson com.fasterxml.jackson.databind.ObjectMapper. The features should be a name that matches a enum from com.fasterxml.jackson.databind.SerializationFeature, com.fasterxml.jackson.databind.DeserializationFeature, or com.fasterxml.jackson.databind.MapperFeature Multiple features can be separated by comma

String

camel.dataformat.json-xstream.enable-jaxb-annotation-module

Whether to enable the JAXB annotations module when using jackson. When enabled then JAXB annotations can be used by Jackson.

false

Boolean

camel.dataformat.json-xstream.enabled

Enable json-xstream dataformat

true

Boolean

camel.dataformat.json-xstream.include

If you want to marshal a pojo to JSON, and the pojo has some fields with null values. And you want to skip these null values, you can set this option to NON_NULL

String

camel.dataformat.json-xstream.json-view

When marshalling a POJO to JSON you might want to exclude certain fields from the JSON output. With Jackson you can use JSON views to accomplish this. This option is to refer to the class which has JsonView annotations

Class

camel.dataformat.json-xstream.module-class-names

To use custom Jackson modules com.fasterxml.jackson.databind.Module specified as a String with FQN class names. Multiple classes can be separated by comma.

String

camel.dataformat.json-xstream.module-refs

To use custom Jackson modules referred from the Camel registry. Multiple modules can be separated by comma.

String

camel.dataformat.json-xstream.object-mapper

Lookup and use the existing ObjectMapper with the given id when using Jackson.

String

camel.dataformat.json-xstream.permissions

Adds permissions that controls which Java packages and classes XStream is allowed to use during unmarshal from xml/json to Java beans. A permission must be configured either here or globally using a JVM system property. The permission can be specified in a syntax where a plus sign is allow, and minus sign is deny. Wildcards is supported by using . as prefix. For example to allow com.foo and all subpackages then specfy com.foo.. Multiple permissions can be configured separated by comma, such as com.foo.,-com.foo.bar.MySecretBean. The following default permission is always included: -,java.lang.,java.util. unless its overridden by specifying a JVM system property with they key org.apache.camel.xstream.permissions.

String

camel.dataformat.json-xstream.pretty-print

To enable pretty printing output nicely formatted. Is by default false.

false

Boolean

camel.dataformat.json-xstream.timezone

If set then Jackson will use the Timezone when marshalling/unmarshalling. This option will have no effect on the others Json DataFormat, like gson, fastjson and xstream.

String

camel.dataformat.json-xstream.unmarshal-type-name

Class name of the java type to use when unarmshalling

String

camel.dataformat.json-xstream.use-default-object-mapper

Whether to lookup and use default Jackson ObjectMapper from the registry.

true

Boolean

camel.dataformat.json-xstream.use-list

To unarmshal to a List of Map or a List of Pojo.

false

Boolean

camel.dataformat.xstream.aliases

Alias a Class to a shorter name to be used in XML elements.

Map

camel.dataformat.xstream.content-type-header

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.

false

Boolean

camel.dataformat.xstream.converters

List of class names for using custom XStream converters. The classes must be of type com.thoughtworks.xstream.converters.Converter

List

camel.dataformat.xstream.driver

To use a custom XStream driver. The instance must be of type com.thoughtworks.xstream.io.HierarchicalStreamDriver

String

camel.dataformat.xstream.driver-ref

To refer to a custom XStream driver to lookup in the registry. The instance must be of type com.thoughtworks.xstream.io.HierarchicalStreamDriver

String

camel.dataformat.xstream.enabled

Enable xstream dataformat

true

Boolean

camel.dataformat.xstream.encoding

Sets the encoding to use

String

camel.dataformat.xstream.implicit-collections

Adds a default implicit collection which is used for any unmapped XML tag.

Map

camel.dataformat.xstream.mode

Mode for dealing with duplicate references The possible values are: NO_REFERENCES ID_REFERENCES XPATH_RELATIVE_REFERENCES XPATH_ABSOLUTE_REFERENCES SINGLE_NODE_XPATH_RELATIVE_REFERENCES SINGLE_NODE_XPATH_ABSOLUTE_REFERENCES

String

camel.dataformat.xstream.omit-fields

Prevents a field from being serialized. To omit a field you must always provide the declaring type and not necessarily the type that is converted.

Map

camel.dataformat.xstream.permissions

Adds permissions that controls which Java packages and classes XStream is allowed to use during unmarshal from xml/json to Java beans. A permission must be configured either here or globally using a JVM system property. The permission can be specified in a syntax where a plus sign is allow, and minus sign is deny. Wildcards is supported by using . as prefix. For example to allow com.foo and all subpackages then specfy com.foo.. Multiple permissions can be configured separated by comma, such as com.foo.,-com.foo.bar.MySecretBean. The following default permission is always included: -,java.lang.,java.util. unless its overridden by specifying a JVM system property with they key org.apache.camel.xstream.permissions.

String

ND

Using the Java DSL

// lets turn Object messages into XML then send to MQSeries
from("activemq:My.Queue").
  marshal().xstream().
  to("mqseries:Another.Queue");

If you would like to configure the XStream instance used by the Camel for the message transformation, you can simply pass a reference to that instance on the DSL level.

XStream xStream = new XStream();
xStream.aliasField("money", PurchaseOrder.class, "cash");
// new Added setModel option since Camel 2.14
xStream.setModel("NO_REFERENCES");
...

from("direct:marshal").
  marshal(new XStreamDataFormat(xStream)).
  to("mock:marshaled");

XMLInputFactory and XMLOutputFactory

The XStream library uses the javax.xml.stream.XMLInputFactory and javax.xml.stream.XMLOutputFactory, you can control which implementation of this factory should be used.

The Factory is discovered using this algorithm: 1. Use the javax.xml.stream.XMLInputFactory , javax.xml.stream.XMLOutputFactory system property. 2. Use the lib/xml.stream.properties file in the JRE_HOME directory. 3. Use the Services API, if available, to determine the classname by looking in the META-INF/services/javax.xml.stream.XMLInputFactory, META-INF/services/javax.xml.stream.XMLOutputFactory files in jars available to the JRE. 4. Use the platform default XMLInputFactory,XMLOutputFactory instance.

How to set the XML encoding in Xstream DataFormat?

You can set the encoding of XML in Xstream DataFormat by setting the Exchange’s property with the key Exchange.CHARSET_NAME, or setting the encoding property on Xstream from DSL or Spring config.

from("activemq:My.Queue").
  marshal().xstream("UTF-8").
  to("mqseries:Another.Queue");

Setting the type permissions of Xstream DataFormat

In Camel, one can always use its own processing step in the route to filter and block certain XML documents to be routed to the XStream’s unmarhall step. You can set XStream’s type permissions to automatically allow or deny the instantiation of certain types.

The default type permissions setting used by Camel denies all types except for those from java.lang and java.util packages. This setting can be changed by setting System property org.apache.camel.xstream.permissions. Its value is a string of comma-separated permission terms, each representing a type being allowed or denied, depending on whether the term is prefixed with '' (note '' may be omitted) or with '-', respectively.

Each term may contain a wildcard character ''. For example, value "-,java.lang.,java.util." indicates denying all types except for java.lang.* and java.util.* classes. Setting this value to an empty string "" reverts to the default XStream’s type permissions handling which denies certain blacklisted classes and allow others.

The type permissions setting can be extended at an individual XStream DataFormat instance by setting its type permissions property.

    <dataFormats>
        <xstream id="xstream-default"
                 permissions="org.apache.camel.samples.xstream.*"/>
        ...