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, e.g. 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 Details

  • 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