Chapter 188. JSon XStream DataFormat
Available as of Camel version 2.0
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>
188.1. Options
The JSon XStream dataformat supports 19 options, which are listed below.
| Name | Default | Java Type | Description |
|---|---|---|---|
| objectMapper |
| Lookup and use the existing ObjectMapper with the given id when using Jackson. | |
| useDefaultObjectMapper |
|
| Whether to lookup and use default Jackson ObjectMapper from the registry. |
| prettyPrint |
|
| To enable pretty printing output nicely formatted. Is by default false. |
| library |
|
| Which json library to use. |
| unmarshalTypeName |
| Class name of the java type to use when unarmshalling | |
| jsonView |
| 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 | |
| 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 | |
| allowJmsType |
|
| Used for JMS users to allow the JMSType header from the JMS spec to specify a FQN classname to use to unmarshal to. |
| collectionTypeName |
| 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. | |
| useList |
|
| To unarmshal to a List of Map or a List of Pojo. |
| enableJaxbAnnotationModule |
|
| Whether to enable the JAXB annotations module when using jackson. When enabled then JAXB annotations can be used by Jackson. |
| moduleClassNames |
| 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. | |
| moduleRefs |
| To use custom Jackson modules referred from the Camel registry. Multiple modules can be separated by comma. | |
| enableFeatures |
| 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 | |
| disableFeatures |
| 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 | |
| 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. | |
| allowUnmarshallType |
|
| 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. |
| 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. | |
| contentTypeHeader |
|
| 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. |
188.2. 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");188.3. 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.
188.4. How to set the XML encoding in Xstream DataFormat?
From Camel 2.2.0, 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");188.5. 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. From Camel 2.16.1, 2.15.5, 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.*"/>
...