# Transformer
Date: 2013-02-18

## org.simpleframework.xml.transform
Class Transformer

    java.lang.Object
      org.simpleframework.xml.transform.Transformer

    public class Transformer

extends java.lang.Object

The `Transformer` object is used to convert strings to and from object instances. This is used during the serialization and deserialization process to transform types from the Java class libraries, as well as other types which do not contain XML schema annotations. Typically this will be used to transform primitive types to and from strings, such as `int` values.

        @Element
        private String[] value;

For example taking the above value the array of strings needs to be converted in to a single string value that can be inserted in to the element in such a way that in can be read later. In this case the serialized value of the string array would be as follows.

        <value>one, two, three</value>

Here each non-null string is inserted in to a comma separated list of values, which can later be deserialized. Just to note the above array could be annotated with `ElementList` just as easily, in which case each entry would have its own element. The choice of which annotation to use is up to the developer. A more obvious benefit to transformations like this can be seen for values annotated with the `Attribute` annotation.

Author:
  Niall Gallagher

Constructor Summary
`Transformer(Matcher matcher)` Constructor for the `Transformer` object.

Method Summary
`java.lang.Object` `read(java.lang.String value, java.lang.Class type)` This method is used to convert the string value given to an appropriate representation.
`boolean` `valid(java.lang.Class type)` This method is used to determine if the type specified can be transformed.
`java.lang.String` `write(java.lang.Object value, java.lang.Class type)` This method is used to convert the provided value into an XML usable format.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### Transformer

    public Transformer(Matcher matcher)

  Constructor for the `Transformer` object. This is used to create a transformer which will transform specified types using transforms loaded from the class path. Transforms are matched to types using the specified matcher object.

  Parameters:
    `matcher` - this is used to match types to transforms

Method Detail

### read

    public java.lang.Object read(java.lang.String value,
                                 java.lang.Class type)
                          throws java.lang.Exception

  This method is used to convert the string value given to an appropriate representation. This is used when an object is being deserialized from the XML document and the value for the string representation is required.

  Parameters:
    `value` - this is the string representation of the value
    `type` - this is the type to convert the string value to
  Returns:
    this returns an appropriate instanced to be used
  Throws:
    `java.lang.Exception`

### write

    public java.lang.String write(java.lang.Object value,
                                  java.lang.Class type)
                           throws java.lang.Exception

  This method is used to convert the provided value into an XML usable format. This is used in the serialization process when there is a need to convert a field value in to a string so that that value can be written as a valid XML entity.

  Parameters:
    `value` - this is the value to be converted to a string
    `type` - this is the type to convert to a string value
  Returns:
    this is the string representation of the given value
  Throws:
    `java.lang.Exception`

### valid

    public boolean valid(java.lang.Class type)
                  throws java.lang.Exception

  This method is used to determine if the type specified can be transformed. This will use the `Matcher` to find a suitable transform, if one exists then this returns true, if not then this returns false. This is used during serialization to determine how to convert a field or method parameter.

  Parameters:
    `type` - the type to determine whether its transformable
  Returns:
    true if the type specified can be transformed by this
  Throws:
    `java.lang.Exception`