Package org.apache.commons.configuration2.beanutils

# Class XMLBeanDeclaration

java.lang.Object
org.apache.commons.configuration2.beanutils.XMLBeanDeclaration

All Implemented Interfaces:
  `BeanDeclaration`

Direct Known Subclasses:
  `ConfigurationDeclaration`

public class XMLBeanDeclaration extends Object implements BeanDeclaration

An implementation of the `BeanDeclaration` interface that is suitable for XML configuration files.

This class defines the standard layout of a bean declaration in an XML configuration file. Such a declaration must look like the following example fragment:

       ...
       <personBean config-class="my.model.PersonBean"
           lastName="Doe" firstName="John">
           <config-constrarg config-value="ID03493" config-type="java.lang.String"/>
           <address config-class="my.model.AddressBean"
               street="21st street 11" zip="1234"
               city="TestCity"/>
       </personBean>

The bean declaration can be contained in an arbitrary element. Here it is the `personBean` element. In the attributes of this element there can occur some reserved attributes, which have the following meaning:

`config-class`
  Here the full qualified name of the bean's class can be specified. An instance of this class will be created. If this attribute is not specified, the bean class must be provided in another way, for example as the `defaultClass` passed to the `BeanHelper` class.
`config-factory`
  This attribute can contain the name of the `BeanFactory` that should be used for creating the bean. If it is defined, a factory with this name must have been registered at the `BeanHelper` class. If this attribute is missing, the default bean factory will be used.
`config-factoryParam`
  With this attribute a parameter can be specified that will be passed to the bean factory. This may be useful for custom bean factories.

All further attributes starting with the `config-` prefix are considered as meta data and will be ignored. All other attributes are treated as properties of the bean to be created, i.e. corresponding setter methods of the bean will be invoked with the values specified here.

If the bean to be created has also some complex properties (which are itself beans), their values cannot be initialized from attributes. For this purpose nested elements can be used. The example listing shows how an address bean can be initialized. This is done in a nested element whose name must match the name of a property of the enclosing bean declaration. The format of this nested element is exactly the same as for the bean declaration itself, i.e. it can have attributes defining meta data or bean properties and even further nested elements for complex bean properties.

If the bean should be created using a specific constructor, the constructor arguments have to be specified. This is done by an arbitrary number of nested `<config-constrarg>` elements. Each element can either have the `config-value` attribute - then it defines a simple value - or must be again a bean declaration (conforming to the format defined here) defining the complex value of this constructor argument.

A `XMLBeanDeclaration` object is usually created from a `HierarchicalConfiguration`. From this it will derive a `SubnodeConfiguration`, which is used to access the needed properties. This subnode configuration can be obtained using the `getConfiguration()` method. All of its properties can be accessed in the usual way. To ensure that the property keys used by this class are understood by the configuration, the default expression engine will be set.

Since:
  1.3

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `static final String`
  `ATTR_BEAN_CLASS`
  Constant for the bean class attribute.
  `static final String`
  `ATTR_BEAN_FACTORY`
  Constant for the bean factory attribute.
  `static final String`
  `ATTR_FACTORY_PARAM`
  Constant for the bean factory parameter attribute.
  `static final String`
  `ATTR_PREFIX`
  Constant for the prefix for reserved attributes.
  `static final String`
  `RESERVED_PREFIX`
  Constant for the prefix of reserved attributes.

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `XMLBeanDeclaration(HierarchicalConfiguration<T> config)`
  Constructs a new instance of `XMLBeanDeclaration` and initializes it from the given configuration.
  `XMLBeanDeclaration(HierarchicalConfiguration<T> config, String key)`
  Constructs a new instance of `XMLBeanDeclaration` and initializes it from the given configuration.
  `XMLBeanDeclaration(HierarchicalConfiguration<T> config, String key, boolean optional)`
  Constructs a new instance of `XMLBeanDeclaration` and initializes it from the given configuration supporting optional declarations.
  `XMLBeanDeclaration(HierarchicalConfiguration<T> config, String key, boolean optional, String defBeanClsName)`
  Constructs a new instance of `XMLBeanDeclaration` and initializes it from the given configuration supporting optional declarations and a default bean class name.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `protected Set<String>`
  `getAttributeNames()`
  Gets a set with the names of the attributes of the configuration node holding the data of this bean declaration.
  `String`
  `getBeanClassName()`
  Gets the name of the class of the bean to be created.
  `String`
  `getBeanFactoryName()`
  Gets the name of the bean factory.
  `Object`
  `getBeanFactoryParameter()`
  Gets a parameter for the bean factory.
  `Map<String,Object>`
  `getBeanProperties()`
  Gets a map with the bean's (simple) properties.
  `HierarchicalConfiguration<?>`
  `getConfiguration()`
  Gets the configuration object this bean declaration is based on.
  `Collection<ConstructorArg>`
  `getConstructorArgs()`
  Gets a collection with constructor arguments.
  `String`
  `getDefaultBeanClassName()`
  Gets the name of the default bean class.
  `Map<String,Object>`
  `getNestedBeanDeclarations()`
  Gets a map with bean declarations for the complex properties of the bean to be created.
  `protected Object`
  `interpolate(Object value)`
  Performs interpolation for the specified value.
  `protected boolean`
  `isReservedAttributeName(String name)`
  Tests if the specified attribute name is reserved and thus does not point to a property of the bean to be created.
  `protected boolean`
  `isReservedChildName(String name)`
  Tests if the specified child node name is reserved and thus should be ignored.
  `protected boolean`
  `isReservedName(String name)`
  Tests if the specified name of a node or attribute is reserved and thus should be ignored.

  ### Methods inherited from class java.lang.Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Field Details

  - ### RESERVED_PREFIX

    public static final String RESERVED_PREFIX
    Constant for the prefix of reserved attributes.
    See Also:
      - Constant Field Values

  - ### ATTR_PREFIX

    public static final String ATTR_PREFIX
    Constant for the prefix for reserved attributes.
    See Also:
      - Constant Field Values

  - ### ATTR_BEAN_CLASS

    public static final String ATTR_BEAN_CLASS
    Constant for the bean class attribute.
    See Also:
      - Constant Field Values

  - ### ATTR_BEAN_FACTORY

    public static final String ATTR_BEAN_FACTORY
    Constant for the bean factory attribute.
    See Also:
      - Constant Field Values

  - ### ATTR_FACTORY_PARAM

    public static final String ATTR_FACTORY_PARAM
    Constant for the bean factory parameter attribute.
    See Also:
      - Constant Field Values

- ## Constructor Details

  - ### XMLBeanDeclaration

    public XMLBeanDeclaration(HierarchicalConfiguration<T> config)
    Constructs a new instance of `XMLBeanDeclaration` and initializes it from the given configuration. The configuration's root node must contain the bean declaration.
    Type Parameters:
      `T` - the node type of the configuration
    Parameters:
      `config` - the configuration with the bean declaration

  - ### XMLBeanDeclaration

    public XMLBeanDeclaration(HierarchicalConfiguration<T> config, String key)
    Constructs a new instance of `XMLBeanDeclaration` and initializes it from the given configuration. The passed in key points to the bean declaration.
    Type Parameters:
      `T` - the node type of the configuration
    Parameters:
      `config` - the configuration (must not be null)
      `key` - the key to the bean declaration (this key must point to exactly one bean declaration or a `IllegalArgumentException` exception will be thrown)
    Throws:
      `IllegalArgumentException` - if required information is missing to construct the bean declaration

  - ### XMLBeanDeclaration

    public XMLBeanDeclaration(HierarchicalConfiguration<T> config, String key, boolean optional)
    Constructs a new instance of `XMLBeanDeclaration` and initializes it from the given configuration supporting optional declarations.
    Type Parameters:
      `T` - the node type of the configuration
    Parameters:
      `config` - the configuration (must not be null)
      `key` - the key to the bean declaration
      `optional` - a flag whether this declaration is optional; if set to true, no exception will be thrown if the passed in key is undefined
    Throws:
      `IllegalArgumentException` - if required information is missing to construct the bean declaration

  - ### XMLBeanDeclaration

    public XMLBeanDeclaration(HierarchicalConfiguration<T> config, String key, boolean optional, String defBeanClsName)
    Constructs a new instance of `XMLBeanDeclaration` and initializes it from the given configuration supporting optional declarations and a default bean class name. The passed in key points to the bean declaration. If the key does not exist and the boolean argument is true, the declaration is initialized with an empty configuration. It is possible to create objects from such an empty declaration if a default class is provided. If the key on the other hand has multiple values or is undefined and the boolean argument is false, a `IllegalArgumentException` exception will be thrown. It is possible to set a default bean class name; this name is used if the configuration does not contain a bean class.
    Type Parameters:
      `T` - the node type of the configuration
    Parameters:
      `config` - the configuration (must not be null)
      `key` - the key to the bean declaration
      `optional` - a flag whether this declaration is optional; if set to true, no exception will be thrown if the passed in key is undefined
      `defBeanClsName` - a default bean class name
    Throws:
      `IllegalArgumentException` - if required information is missing to construct the bean declaration
    Since:
      2.0

- ## Method Details

  - ### getAttributeNames

    protected Set<String> getAttributeNames()
    Gets a set with the names of the attributes of the configuration node holding the data of this bean declaration.
    Returns:
      the attribute names of the underlying configuration node

  - ### getBeanClassName

    public String getBeanClassName()
    Gets the name of the class of the bean to be created. This information is obtained from the `config-class` attribute.
    Specified by:
      `getBeanClassName` in interface `BeanDeclaration`
    Returns:
      the name of the bean's class

  - ### getBeanFactoryName

    public String getBeanFactoryName()
    Gets the name of the bean factory. This information is fetched from the `config-factory` attribute.
    Specified by:
      `getBeanFactoryName` in interface `BeanDeclaration`
    Returns:
      the name of the bean factory

  - ### getBeanFactoryParameter

    public Object getBeanFactoryParameter()
    Gets a parameter for the bean factory. This information is fetched from the `config-factoryParam` attribute.
    Specified by:
      `getBeanFactoryParameter` in interface `BeanDeclaration`
    Returns:
      the parameter for the bean factory

  - ### getBeanProperties

    public Map<String,Object> getBeanProperties()
    Gets a map with the bean's (simple) properties. The properties are collected from all attribute nodes, which are not reserved.
    Specified by:
      `getBeanProperties` in interface `BeanDeclaration`
    Returns:
      a map with the bean's properties

  - ### getConfiguration

    public HierarchicalConfiguration<?> getConfiguration()
    Gets the configuration object this bean declaration is based on.
    Returns:
      the associated configuration

  - ### getConstructorArgs

    public Collection<ConstructorArg> getConstructorArgs()
    Gets a collection with constructor arguments. This data is used to determine the constructor of the bean class to be invoked. The values of the arguments are passed to the constructor. An implementation can return null or an empty collection; then the standard constructor of the bean class is called. This implementation processes all child nodes with the name `config-constrarg`. If such a node has a `config-class` attribute, it is considered a nested bean declaration; otherwise it is interpreted as a simple value. If no nested constructor argument declarations are found, result is an empty collection.
    Specified by:
      `getConstructorArgs` in interface `BeanDeclaration`
    Returns:
      a collection with the arguments to be passed to the bean class's constructor

  - ### getDefaultBeanClassName

    public String getDefaultBeanClassName()
    Gets the name of the default bean class. This class is used if no bean class is specified in the configuration. It may be null if no default class was set.
    Returns:
      the default bean class name
    Since:
      2.0

  - ### getNestedBeanDeclarations

    public Map<String,Object> getNestedBeanDeclarations()
    Gets a map with bean declarations for the complex properties of the bean to be created. These declarations are obtained from the child nodes of this declaration's root node.
    Specified by:
      `getNestedBeanDeclarations` in interface `BeanDeclaration`
    Returns:
      a map with bean declarations for complex properties

  - ### interpolate

    protected Object interpolate(Object value)
    Performs interpolation for the specified value. This implementation will interpolate against the current subnode configuration's parent. If sub classes need a different interpolation mechanism, they should override this method.
    Parameters:
      `value` - the value that is to be interpolated
    Returns:
      the interpolated value

  - ### isReservedAttributeName

    protected boolean isReservedAttributeName(String name)
    Tests if the specified attribute name is reserved and thus does not point to a property of the bean to be created. This method is called when processing the attributes of this bean declaration. It is then possible to ignore some attributes with a specific meaning. This implementation delegates to `isReservedName(String)`.
    Parameters:
      `name` - the name of the attribute to be checked
    Returns:
      a flag whether this name is reserved
    Since:
      2.0

  - ### isReservedChildName

    protected boolean isReservedChildName(String name)
    Tests if the specified child node name is reserved and thus should be ignored. This method is called when processing child nodes of this bean declaration. It is then possible to ignore some nodes with a specific meaning. This implementation delegates to `isReservedName(String)`.
    Parameters:
      `name` - the name of the child node to be checked
    Returns:
      a flag whether this name is reserved
    Since:
      2.0

  - ### isReservedName

    protected boolean isReservedName(String name)
    Tests if the specified name of a node or attribute is reserved and thus should be ignored. This method is called per default by the methods for checking attribute and child node names. It checks whether the passed in name starts with the reserved prefix.
    Parameters:
      `name` - the name to be checked
    Returns:
      a flag whether this name is reserved