Converters
The core of XStream consists of a registry of Converters. The responsibility of a Converter is to provide a strategy for converting particular types of objects found in the object graph, to and from XML.
XStream is provided with Converters for common types such as primitives, String, File, Collections, arrays, and Dates. The following table lists any converter delivered with XStream and documents, if they are registered by default with which priority.
java.lang (and core special types) |
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| Converter | Supported types | Example | Notes | Prio |
|---|---|---|---|---|
| NullConverter | null values | <null/> | Usually, null fields are left out of the XML, however when used in arrays or the root object they have to be explicitly marked. | very high |
| ArrayConverter | any kind of array |
<string-array> <string>apple</string> <string>banana</string> <string>cabbage</string> <string-array> |
This supports arrays of primitives as well as objects. It also supports multi-dimensional arrays, even if they are non-rectangular. | normal |
| BooleanConverter | boolean java.lang.Boolean |
<boolean>true</boolean> | Can also be registered locally using different values. | normal |
| ByteConverter | byte java.lang.Byte |
<byte>22</byte> | The byte is represented as an integer. | normal |
| EncodedByteArrayConverter | byte[] | <byte-array>AHiEFiEABQ==</byte-array> | Uses Base64 encoding to store binary data in XML. Converter can be registered globally or locally. | normal |
| CharConverter | char java.lang.Character |
<char>X</char> <char null="true"/> |
The '\0' character is invalid in XML. | normal |
| CharArrayConverter | char[] | <char-array>hello<char-array> | Joins all characters into a single String. | normal |
| DoubleConverter | double java.lang.Double |
<double>456774543443.4553435</double> | normal | |
| FloatConverter | float java.lang.Float |
<float>4563443.435</float> | normal | |
| IntConverter | int java.lang.Integer |
<int>12345678</int> | normal | |
| LongConverter | long java.lang.Long |
<long>2344556678888786</long> | normal | |
| NamedArrayConverter | any kind of array |
<string-array> <product>apple</product> <product>banana</product> <product>cabbage</product> <string-array> |
This supports arrays of primitives as well as objects. It also supports multi-dimensional arrays, even if they are non-rectangular. Should be registered locally or for an individual array type. | |
| ShortConverter | short java.lang.Short |
<short>1445</short> | normal | |
| StringConverter | java.lang.String | <string>hello world</string> | This converter can be registered with different caching strategies. | normal |
| StringBufferConverter | java.lang.StringBuffer | <string-buffer>hello world</string-buffer> | normal | |
| StringBuilderConverter | java.lang.StringBuilder | <string-builder>hello world</string-builder> | Available under Java 1.5 or greater. | normal |
| ThrowableConverter | java.lang.Throwable java.lang.Exception java.lang.RuntimeException java.lang.Error ...and all subclasses of these. |
<java.io.IOException> <detailMessage>No file</detailMessage> <stack-trace> <trace>com.x.Foo.stuff(Foo.java:22)</trace> <trace>com.x.Foo.blah(Foo.java:31)</trace> <trace>com.x.Foo.main(Foo.java:43)</trace> </stack-trace> </java.io.IOException> |
This is only available under Java 1.4 or greater. It retains the full stack trace, including that of any nested exceptions. The stack trace elements are handled by the StackTraceElementConverter. | normal |
| EnumConverter | java.lang.Enum | <java.lang.annotation.RetentionPolicy> CLASS </java.lang.annotation.RetentionPolicy> |
Available under Java 1.5 or greater. | normal |
| EnumToStringConverter | java.lang.Enum | The Converter must be initialized with an Enum type and an optional mapping between strings and enum values. By default it will use the Enum's string representation as value. | Available under Java 1.5 or greater. Must be registered explicitly for the Enum type or locally. | |
java.util |
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| Converter | Supported types | Example | Notes | Prio |
| CollectionConverter | java.util.ArrayList java.util.LinkedList java.util.HashSet java.util.Vector java.util.LinkedHashSet |
<linked-list> <string>apple</string> <string>banana</string> <big-decimal>12345.4555</big-decimal> </linked-list> |
The objects inside the collection can be any type of objects, including nested collections. Can be registered for an individual Collection type or locally, suppression of implicit type might be necessary. | normal |
| MapConverter | java.util.HashMap java.util.Hashtable java.util.LinkedHashMap java.util.concurrent.ConcurrentHashMap |
<map> <entry> <string>apple</string> <float>123.553</float> </entry> <entry> <string>orange</string> <float>55.4</float> </entry> </map> |
Both key and values can be any type of objects. Can be registered for an individual Map type or locally, suppression of implicit type might be necessary. | normal |
| NamedCollectionConverter | java.util.ArrayList java.util.LinkedList java.util.HashSet java.util.Vector java.util.LinkedHashSet |
<fruits> <fruit>apple</fruit> <fruit>banana</fruit> <fruit>orange</fruit> </fruits> |
The objects inside the collection can be of any type shared between the objects. Should be registered locally or for an individual Collection type. | |
| NamedMapConverter | java.util.HashMap java.util.Hashtable java.util.LinkedHashMap java.util.concurrent.ConcurrentHashMap |
<map> <fruit> <name>apple</name> <price>123.553</price> </fruit> <fruit> <name>orange</name> <price>55.4</price> </fruit> </map> |
Both key and values can be any type of objects. If key or value are written as attributes or if the value is written as text of the entry element, those types must be handled by a SingleValueConverter. Should be registered locally or for an individual Map type. | |
| PropertiesConverter | java.util.Properties |
<properties> <property name="host" value="localhost"/> <property name="port" value="888"/> </properties> |
Because the Properties class only accepts Strings for keys and values, the XML can be more concise.
If the Properties instance includes a set of default Properties, these are serialized in a nested <defaults> element. |
normal |
| SingletonCollectionConverter | java.util.Collections.singletonList().getClass() java.util.Collections.singleton().getClass() |
<singleton-set> <string>apple</string> </singleton-set> |
The objects inside the singleton collection can be any type of objects, including nested collections. | normal |
| SingletonMapConverter | java.util.Collections.singletonMap().getClass() |
<singleton-map> <entry> <string>apple</string> <float>123.553</float> </entry> </singleton-map> |
The objects inside the singleton collection can be any type of objects, including nested collections. | normal |
| TreeMapConverter | java.util.TreeMap |
<tree-map> <comparator class="com.blah.MyComparator"/> <entry> <string>apple</string> <float>123.553</float> </entry> <entry> <string>orange</string> <float>55.4</float> </entry> </tree-map> |
This is similar to MapConverter with an additional field for storing the java.util.Comparator associated with the TreeMap. | normal |
| TreeSetConverter | java.util.TreeSet |
<tree-set> <comparator class="com.blah.MyComparator"/> <string>apple</string> <string>banana</string> <string>cabbage</string> </tree-set> |
This is similar to CollectionConverter with an additional field for storing the java.util.Comparator associated with the TreeSet. | normal |
| BitSetConverter | java.util.BitSet | <bit-set>0,1,3,5,6,8,10</bit-set> | Stores a comma separated list of which bits are set. Designed to be readable without taking up too much space. | normal |
| DateConverter | java.util.Date | <date>2004-02-22 15:16:04.0 UTC</date> | Can be registered with different formats, locales or time zone globally or locally. | normal |
| GregorianCalendarConverter | java.util.Calendar java.util.GregorianCalendar |
<gregorian-calendar> <time>555454646</time> </gregorian-calendar> |
normal | |
| ISO8601DateConverter | java.util.Date | <date>2006-07-28T12:06:17.654-03:00</date> | Not automatically registered, can be used globally or locally. Implementation needs joda-time. | |
| ISO8601GregorianCalendarConverter | java.util.GregorianCalendar |
<gregorian-calendar> 2006-07-28T12:07:02.788-03:00 </gregorian-calendar> |
Not automatically registered, can be used globally or locally. Implementation needs joda-time. | |
| LocaleConverter | java.util.Locale | <locale>en_GB</locale> | normal | |
| CurrencyConverter | java.util.Currency | <currency>USD</currency> | Available under Java 1.4 or greater. | normal |
| UUIDConverter | java.util.UUID | <uuid>ca05f023-e07f-4956-a6ef-14ddd23df47b</uuid> | Available under Java 1.5 or greater. | normal |
| EnumMapConverter | java.util.EnumMap |
<enum-map enum-type="simple"> <entry> <simple>GREEN</simple> <string>grass</string> </entry> <entry> <simple>BLUE</simple> <string>sky</string> </entry> </enum-map> |
Available under Java 1.5 or greater. | normal |
| EnumSetConverter | java.util.EnumSet |
<enum-set enum-type="simple"> GREEN,BLUE </enum-set> |
Available under Java 1.5 or greater. | normal |
| RegexPatternConverter | java.util.regex.Pattern |
<java.util.regex.Pattern> <pattern>.*</pattern> <flags>0</flags> </java.util.regex.Pattern> |
Available under Java 1.4 or greater. | normal |
java.sql |
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| Converter | Supported types | Example | Notes | Prio |
| SqlDateConverter | java.sql.Date | <sql-date>1978-08-25</sql-date> | Only automatically registered if runtime has JDBC support. | normal |
| SqlTimeConverter | java.sql.Time | <sql-time>14:07:33</sql-time> | Only automatically registered if runtime has JDBC support. | normal |
| SqlTimestampConverter | java.sql.Timestamp | <sql-timestamp>1970-01-01 00:00:01.234</sql-timestamp> | Only automatically registered if runtime has JDBC support. | normal |
| ISO8601SqlTimestampConverter | java.sql.Timestamp | <sql-timestamp>2006-07-28T12:06:17.654000000-03:00</sql-timestamp> | Not automatically registered, can be used globally or locally. Implementation needs joda-time. | |
java.math |
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| Converter | Supported types | Example | Notes | Prio |
| BigDecimalConverter | java.math.BigDecimal | <big-decimal>342346.445332</big-decimal> | normal | |
| BigIntegerConverter | java.math.BigInteger | <big-int>23434224556</big-int> | normal | |
java.net |
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| Converter | Supported types | Example | Notes | Prio |
| URIConverter | java.net.URI | <uri>mailto:xstream-user.codehaus.org</uri> | normal | |
| URLConverter | java.net.URL | <url>http://codehaus.org/blah</url> | normal | |
java.io |
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| Converter | Supported types | Example | Notes | Prio |
| FileConverter | java.io.File | <file>/stuff/hello.txt</file> | normal | |
| SerializableConverter | java.io.Serializable | See description at Generalized Converters. | low | |
| ExternalizableConverter | java.io.Externalizable |
<externalizable-type> <string>apple</string> <int>42</int> <big-decimal>12345.4555</big-decimal> </externalizable-type> |
See description at Generalized Converters. | low |
java.nio |
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| Converter | Supported types | Example | Notes | Prio |
| CharsetConverter | java.nio.charset.Charset | <charset>US-ASCII</charset> | Available under Java 1.4 or greater. | normal |
| PathConverter | java.nio.file.Path | <path>../dir/file.txt</path> | Available under Java 1.7 or greater. | normal |
java.lang.reflect |
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| Converter | Supported types | Example | Notes | Prio |
| JavaClassConverter | java.lang.Class | <class>com.foo.MyThing</class> | This converter uses the ClassLoaderReference of the XStream insatance. Can be regisreted with Mapper globally or locally to respect type aliases. | normal |
| JavaFieldConverter | java.lang.reflect.Field |
<field> <name>myField</name> <class>com.foo.MyThing</class> </field> |
This converter uses the ClassLoaderReference of the XStream insatance. Can be regisreted with Mapper globally or locally to respect type aliases. | normal |
| JavaMethodConverter | java.lang.reflect.Method java.lang.reflect.Constructor |
<method> <class>com.foo.MyThing</class> <name>doStuff</name> <parameter-types> <class>java.lang.String</class> <class>java.util.Iterator</class> </parameter-types> </method> |
The enclosing element for this tag will either by <method> or <constructor>. This converter uses the ClassLoaderReference of the XStream insatance. Can be regisreted with Mapper globally or locally to respect type aliases. | normal |
| DynamicProxyConverter | Any dynamic proxy generated by java.lang.reflect.Proxy |
<dynamic-proxy> <interface>com.foo.Blah</interface> <interface>com.foo.Woo</interface> <handler class="com.foo.MyHandler"> <something>blah</something> </handler> </dynamic-proxy> |
The dynamic proxy itself is not serialized, however the interfaces it implements and the actual InvocationHandler instance are serialized. This allows the proxy to be reconstructed after deserialization. | normal |
java.awt |
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| Converter | Supported types | Example | Notes | Prio |
| ColorConverter | java.awt.Color |
<awt-color> <red>255</red> <green>255</green> <blue>255</blue> <alpha>255</alpha> </awt-color> |
Only automatically registered if runtime has AWT support. Warning: The AWT toolkit is definitely initialized when a Color is deserialized. |
normal |
| FontConverter | java.awt.Font javax.swing.plaf.FontUIResource |
<awt-font> <family class="string">Arial</family> <size class="float">20.0</size> <width class="null"/> <posture class="null"/> <weight class="float">2.0</weight> <superscript class="null"/> </awt-font> |
Only automatically registered if runtime has AWT support. Warning: The AWT toolkit is definitely initialized when a Font is deserialized. |
normal |
java.awt.font |
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| Converter | Supported types | Example | Notes | Prio |
| TextAttributeConverter | java.awt.font.TextAttribute | <awt-text-attribute>family</awt-text-attribute> | Only automatically registered if runtime has AWT support. Warning: The AWT toolkit is definitely initialized when a TextAttribute is deserialized. |
normal |
java.awt.font |
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| Converter | Supported types | Example | Notes | Prio |
| ActivationDataFlavorConverter | javax.activation.ActivationDataFlavor |
<activation-data-flavor> <mimeType>application/x-junit</mimeType> <humanRepresentableName>JUnit</humanRepresentableName> <representationClass>java.io.InputStream</representationClass> </activation-data-flavor> |
Available under Java 1.6 or greater. Only automatically registered if runtime has AWT support. | normal |
javax.swing |
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| Converter | Supported types | Example | Notes | Prio |
| LookAndFeelConverter | javax.swing.LookAndFeel implementations | Only automatically registered if runtime has Swing support. | normal | |
javax.security.auth |
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| Converter | Supported types | Example | Notes | Prio |
| SubjectConverter | javax.security.auth.Subject |
<auth-subject> <principals> <com.thoughtworks.xstream.Admin/> </principals> <readOnly>false</readOnly> </auth-subject> |
Available under Java 1.4 or greater. This converter does not serialize any credentials but only the principals. | normal |
javax.xml.datatype |
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| Converter | Supported types | Example | Notes | Prio |
| DurationConverter | javax.xml.datatype.Duration | <duration>PT1H2M</duration> | Available under Java 1.5 or greater. | normal |
Generalized Converters |
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| Converter | Supported types | Explanation | Notes | Prio |
| ReflectionConverter | Any type | The Converter is used as fallback. It uses reflection to examine the class and will serialize its fields. | very low | |
| AnnotationReflectionConverter | Any type | The Converter is used as fallback. It uses reflection to examine the class and will serialize its fields and supports annotations for local converters. | Needs JDK 1.5, default for JDK 1.5. Deprecated since XStream 1.3 and must be registered now explicitly. | |
| SerializableConverter | java.io.Serializable or types with one of the serializable methods readObject or writeObject | The Converter is used for any JDK-serializable types, if not handled by a specialized Converter. | low | |
| ExternalizableConverter | java.io.Externalizable | The Converter is used for any JDK-externalizable types, if not handled by a specialized Converter. | low | |
| LambdaConverter | For serializable and non-serializable lambda types. Noon-serialzable lambda instances will be mapped to null, since they contain no information for recreation. Serializable lambda types have such info, but it is specific to compiler vendor and occurrence in the code. Never assume that you can deserialize such an element when you use a different version of your code or a different compiler. | Only automatically registered for Java 8. | normal | |
| ToAttributedValueConverter | Any type with all fields to be represented by a single string but one. | The Converter is used to write all but one fields of the type as attributes. The left over field is then used as current value. | Must be registered globally or locally for the appropriate type. | |
| ToStringConverter | Any type with natural String representation | The Converter must be initialized with a type, that provides a complete String representation with its toString() method and is able to be recreated by a constructor taking a single String argument. | Must be registered globally or locally for the appropriate type. | |
| JavaBeanConverter | Java beans | The Converter handles any type as Java bean. It expects the type to convert to have a public default constructor and appropriate getter and setters. | Must be registered globally or locally. Can be used as fallback with priority very low. | |
| PropertyEditorCapableConverter | Any type with a PropertyEditor implementation | The Converter can handles any type that provides a PropertyEditor implementation. The PropertyEditor's methods getAsText() and setAsText() are used to convert between object and string representation. | Must be registered globally or locally for the appropriate type. | |
Converters for 3rd party classes |
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| Converter | Supported types | Explanation | Notes | Add-On |
| CGLIBEnhancedConverter | Proxies generated by the CGLIB Enhancer | The Converter handles proxies generated by the CGLIB Enhancer, if there were not multiple callbacks registered. A proxy with multiple callbacks can currently not be handled at all. | Must be registered globally and in combination with the CGLIBMapper. See FAQ. | xstream |
| HibernatePersistentCollectionConverter | org.hibernate.collection.internal.PersistentBag org.hibernate.collection.internal.PersistentList org.hibernate.collection.internal.PersistentSet org.hibernate.envers.entities.mapper.relation.lazy.proxy.ListProxy org.hibernate.envers.entities.mapper.relation.lazy.proxy.SetProxy |
The Converter handles Hibernate 4 (or 3) standard collections and Envers proxies. It will handle any element of the collection. | Must be registered explicitly in combination with the HibernateMapper and all the other Hibernate converters. See package description. | xstream-hibernate |
| HibernatePersistentMapConverter | org.hibernate.collection.internal.PersistentMap org.hibernate.envers.entities.mapper.relation.lazy.proxy.MapProxy |
The Converter handles unsorted Hibernate 4 (or 3) maps or Envers proxy. It will handle any key and value of the map. | Must be registered explicitly in combination with the HibernateMapper and all the other Hibernate converters. See package description. | xstream-hibernate |
| HibernatePersistentSortedMapConverter | org.hibernate.collection.internal.PersistentSortedMap org.hibernate.envers.entities.mapper.relation.lazy.proxy.SortedMapProxy |
The Converter handles sorted Hibernate 4 (or 3) maps or Envers proxy. It will handle any key and value of the map. | Must be registered explicitly in combination with the HibernateMapper and all the other Hibernate converters. See package description. | xstream-hibernate |
| HibernatePersistentSortedSetConverter | org.hibernate.collection.intrernal.PersistentSortedSet org.hibernate.envers.entities.mapper.relation.lazy.proxy.SortedSetProxy |
The Converter handles sorted Hibernate 4 (or 3) sets or Envers proxy. It will handle any element of the set. | Must be registered explicitly in combination with the HibernateMapper and all the other Hibernate converters. See package description. | xstream-hibernate |
| HibernateProxyConverter | org.hibernate.proxy.HibernateProxy | The Converter handle any element that is wrapped by a Hibernate proxy. | Must be registered explicitly in combination with the HibernateMapper and all the other Hibernate converters. See package description. | xstream-hibernate |