Package 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.

Field Summary

Fields

Modifier and Type	Field	Description
private Cache<Transform>	cache	This is used to cache all transforms matched to a given type.
private Cache<java.lang.Object>	error	This is used to cache the types that to not have a transform.
private Matcher	matcher	This is used to perform the matching of types to transforms.

Constructor Summary

Constructors

Constructor	Description
Transformer(Matcher matcher)	Constructor for the Transformer object.

Method Summary

Modifier and Type	Method	Description
private Transform	lookup(java.lang.Class type)	This method is used to acquire a Transform for the the specified type.
private Transform	match(java.lang.Class type)	This method is used to acquire a Transform for the the specified type.
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

Field Detail

cache

private final Cache<Transform> cache

This is used to cache all transforms matched to a given type.

error

private final Cache<java.lang.Object> error

This is used to cache the types that to not have a transform.

matcher

private final Matcher matcher

This is used to perform the matching of types to transforms.

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

lookup

private Transform lookup(java.lang.Class type)
                  throws java.lang.Exception

This method is used to acquire a Transform for the the specified type. If there is no transform for the type then this will return null. Once acquired once the transform is cached so that subsequent lookups will be performed faster.

Parameters:

type - the type to determine whether its transformable

Returns:

this will return a transform for the specified type

Throws:

java.lang.Exception

match

private Transform match(java.lang.Class type)
                 throws java.lang.Exception

This method is used to acquire a Transform for the the specified type. If there is no transform for the type then this will return null. Once acquired once the transform is cached so that subsequent lookups will be performed faster.

Parameters:

type - the type to determine whether its transformable

Returns:

this will return a transform for the specified type

Throws:

java.lang.Exception