Package org.apache.struts2.conversion.impl

Class XWorkConverter

java.lang.Object
org.apache.struts2.conversion.impl.DefaultTypeConverter
org.apache.struts2.conversion.impl.XWorkConverter
All Implemented Interfaces:
TypeConverter
public class XWorkConverter extends DefaultTypeConverter

XWorkConverter is a singleton used by many of the Struts 2's Ognl extension points, such as InstantiatingNullHandler, XWorkListPropertyAccessor etc to do object conversion.

Type conversion is great for situations where you need to turn a String in to a more complex object. Because the web is type-agnostic (everything is a string in HTTP), Struts 2's type conversion features are very useful. For instance, if you were prompting a user to enter in coordinates in the form of a string (such as "3, 22"), you could have Struts 2 do the conversion both from String to Point and from Point to String.

Using this "point" example, if your action (or another compound object in which you are setting properties on) has a corresponding ClassName-conversion.properties file, Struts 2 will use the configured type converters for conversion to and from strings. So turning "3, 22" in to new Point(3, 22) is done by merely adding the following entry to ClassName-conversion.properties (Note that the PointConverter should impl the TypeConverter interface):

point = com.acme.PointConverter

Your type converter should be sure to check what class type it is being requested to convert. Because it is used for both to and from strings, you will need to split the conversion method in to two parts: one that turns Strings in to Points, and one that turns Points in to Strings.

After this is done, you can now reference your point (using <s:property value="point"/> in JSP or ${point} in FreeMarker) and it will be printed as "3, 22" again. As such, if you submit this back to an action, it will be converted back to a Point once again.

In some situations you may wish to apply a type converter globally. This can be done by editing the file xwork-conversion.properties in the root of your class path (typically WEB-INF/classes) and providing a property in the form of the class name of the object you wish to convert on the left hand side and the class name of the type converter on the right hand side. For example, providing a type converter for all Point objects would mean adding the following entry:

com.acme.Point = com.acme.PointConverter

Type conversion should not be used as a substitute for i18n. It is not recommended to use this feature to print out properly formatted dates. Rather, you should use the i18n features of Struts 2 (and consult the JavaDocs for JDK's MessageFormat object) to see how a properly formatted date should be displayed.

Any error that occurs during type conversion may or may not wish to be reported. For example, reporting that the input "abc" could not be converted to a number might be important. On the other hand, reporting that an empty string, "", cannot be converted to a number might not be important - especially in a web environment where it is hard to distinguish between a user not entering a value vs. entering a blank value.

By default, all conversion errors are reported using the generic i18n key xwork.default.invalid.fieldvalue, which you can override (the default text is Invalid field value for field "xxx", where xxx is the field name) in your global i18n resource bundle.

However, sometimes you may wish to override this message on a per-field basis. You can do this by adding an i18n key associated with just your action (Action.properties) using the pattern invalid.fieldvalue.xxx, where xxx is the field name.

It is important to know that none of these errors are actually reported directly. Rather, they are added to a map called conversionErrors in the ActionContext. There are several ways this map can then be accessed and the errors can be reported accordingly.

Version:
$Date$ $Id$
Author:
Pat Lightbody, Rainer Hermanns, Alexandru Popescu, tm_jee
See Also:

  • Field Details

  • Constructor Details

    • XWorkConverter

      protected XWorkConverter()

  • Method Details

    • setDefaultTypeConverter

      public void setDefaultTypeConverter(XWorkBasicConverter converter)

    • setFileManagerFactory

      public void setFileManagerFactory(FileManagerFactory fileManagerFactory)

    • setReloadingConfigs

      public void setReloadingConfigs(String reloadingConfigs)

    • setConversionFileProcessor

      public void setConversionFileProcessor(ConversionFileProcessor fileProcessor)

    • setConversionAnnotationProcessor

      public void setConversionAnnotationProcessor(ConversionAnnotationProcessor annotationProcessor)

    • setTypeConverterHolder

      public void setTypeConverterHolder(TypeConverterHolder converterHolder)

    • getConversionErrorMessage

      public static String getConversionErrorMessage(String propertyName, Class toClass, ValueStack stack)

    • buildConverterFilename

      public String buildConverterFilename(Class clazz)

    • convertValue

      public Object convertValue(Map<String,Object> map, Object o, Class aClass)
      Overrides:
      convertValue in class DefaultTypeConverter

    • convertValue

      public Object convertValue(Map<String,Object> context, Object target, Member member, String property, Object value, Class toClass)
      Convert value from one form to another. Minimum requirement of arguments:
      • supplying context, toClass and value
      • supplying context, target and value.
      Specified by:
      convertValue in interface TypeConverter
      Overrides:
      convertValue in class DefaultTypeConverter
      Parameters:
      context - context under which the conversion is being done
      target - target object in which the property is being set
      member - member (Constructor, Method or Field) being set
      property - property name being set
      value - value to be converted
      toClass - type to which value is converted
      Returns:
      Converted value of type toType or TypeConverter.NoConversionPossible to indicate that the conversion was not possible.
      See Also:

    • lookup

      public TypeConverter lookup(String className, boolean isPrimitive)
      Looks for a TypeConverter in the default mappings.
      Parameters:
      className - name of the class the TypeConverter must handle
      isPrimitive - is primitive?
      Returns:
      a TypeConverter to handle the specified class or null if none can be found

    • lookup

      public TypeConverter lookup(Class clazz)
      Looks for a TypeConverter in the default mappings.
      Parameters:
      clazz - the class the TypeConverter must handle
      Returns:
      a TypeConverter to handle the specified class or null if none can be found

    • getConverter

      protected Object getConverter(Class clazz, String property)

    • handleConversionException

      protected void handleConversionException(Map<String,Object> context, String property, Object value, Object object, Class toClass)

    • registerConverter

      public void registerConverter(String className, TypeConverter converter)

    • registerConverterNotFound

      public void registerConverterNotFound(String className)

    • addConverterMapping

      protected void addConverterMapping(Map<String,Object> mapping, Class clazz)
      Looks for converter mappings for the specified class and adds it to an existing map. Only new converters are added. If a converter is defined on a key that already exists, the converter is ignored.
      Parameters:
      mapping - an existing map to add new converter mappings to
      clazz - class to look for converter mappings for

    • buildConverterMapping

      protected Map<String,Object> buildConverterMapping(Class clazz) throws Exception
      Looks for converter mappings for the specified class, traversing up its class hierarchy and interfaces and adding any additional mappings it may find. Mappings lower in the hierarchy have priority over those higher in the hierarchy.
      Parameters:
      clazz - the class to look for converter mappings for
      Returns:
      the converter mappings
      Throws:
      Exception - in case of any errors