XMLCatalog (Apache Ant API)
Date: 2016-04-24

org.apache.tools.ant.types

## Class XMLCatalog

- java.lang.Object
- - org.apache.tools.ant.ProjectComponent
  - - org.apache.tools.ant.types.DataType
    - - org.apache.tools.ant.types.XMLCatalog

- All Implemented Interfaces:
    java.lang.Cloneable, javax.xml.transform.URIResolver, org.xml.sax.EntityResolver

      public class XMLCatalog
      extends DataType
      implements java.lang.Cloneable, org.xml.sax.EntityResolver, javax.xml.transform.URIResolver

  This data type provides a catalog of resource locations (such as DTDs and XML entities), based on the OASIS "Open Catalog" standard. The catalog entries are used both for Entity resolution and URI resolution, in accordance with the `EntityResolver` and `URIResolver` interfaces as defined in the Java API for XML Processing Specification.

  Resource locations can be specified either in-line or in external catalog file(s), or both. In order to use an external catalog file, the xml-commons resolver library ("resolver.jar") must be in your classpath. External catalog files may be either plain text format or XML format. If the xml-commons resolver library is not found in the classpath, external catalog files, specified in `<catalogpath>` paths, will be ignored and a warning will be logged. In this case, however, processing of inline entries will proceed normally.

  Currently, only `<dtd>` and `<entity>` elements may be specified inline; these correspond to OASIS catalog entry types `PUBLIC` and `URI` respectively.

  The following is a usage example:

  `<xmlcatalog>
  <dtd publicId="" location="/path/to/file.jar" />
  <dtd publicId="" location="/path/to/file2.jar" />
  <entity publicId="" location="/path/to/file3.jar" />
  <entity publicId="" location="/path/to/file4.jar" />
  <catalogpath>
  <pathelement location="/etc/sgml/catalog"/>
  </catalogpath>
  <catalogfiles dir="/opt/catalogs/" includes="**\catalog.xml" />
  </xmlcatalog>
  `

  Tasks wishing to use `<xmlcatalog>` must provide a method called `createXMLCatalog` which returns an instance of `XMLCatalog`. Nested DTD and entity definitions are handled by the XMLCatalog object and must be labeled `dtd` and `entity` respectively.

  The following is a description of the resolution algorithm: entities/URIs/dtds are looked up in each of the following contexts, stopping when a valid and readable resource is found:

  1. In the local filesystem
  2. In the classpath
  3. Using the Apache xml-commons resolver (if it is available)
  4. In URL-space

  See `XMLValidateTask` for an example of a task that has integrated support for XMLCatalogs.

  Possible future extension could provide for additional OASIS entry types to be specified inline.

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static java.lang.String` | `APACHE_RESOLVER` The name of the bridge to the Apache xml-commons resolver class, used to determine whether resolver.jar is present in the classpath.
    `static java.lang.String` | `CATALOG_RESOLVER` Resolver base class

    - ### Fields inherited from class org.apache.tools.ant.types.DataType

      `checked, ref`

    - ### Fields inherited from class org.apache.tools.ant.ProjectComponent

      `description, location, project`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `XMLCatalog()` Default constructor

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `addConfiguredXMLCatalog(XMLCatalog catalog)` Loads a nested `<xmlcatalog>` into our definition.
    `void` | `addDTD(ResourceLocation dtd)` Creates the nested `<dtd>` element.
    `void` | `addEntity(ResourceLocation entity)` Creates the nested `<entity>` element.
    `Path` | `createCatalogPath()` Creates a nested `<catalogpath>` element.
    `Path` | `createClasspath()` Allows nested classpath elements.
    `protected void` | `dieOnCircularReference(java.util.Stack<java.lang.Object> stk, Project p)` Check to see whether any DataType we hold references to is included in the Stack (which holds all DataType instances that directly or indirectly reference this instance, including this instance itself).
    `Path` | `getCatalogPath()` Returns the catalog path in which to attempt to resolve DTDs.
    `javax.xml.transform.Source` | `resolve(java.lang.String href, java.lang.String base)` Implements the URIResolver.resolve() interface method.
    `org.xml.sax.InputSource` | `resolveEntity(java.lang.String publicId, java.lang.String systemId)` Implements the EntityResolver.resolveEntity() interface method.
    `void` | `setCatalogPathRef(Reference r)` Allows catalogpath reference.
    `void` | `setClasspath(Path classpath)` Allows simple classpath string.
    `void` | `setClasspathRef(Reference r)` Allows classpath reference.
    `void` | `setRefid(Reference r)` Makes this instance in effect a reference to another XMLCatalog instance.

    - ### Methods inherited from class org.apache.tools.ant.types.DataType

      `checkAttributesAllowed, checkChildrenAllowed, circularReference, clone, dieOnCircularReference, dieOnCircularReference, getCheckedRef, getCheckedRef, getCheckedRef, getCheckedRef, getDataTypeName, getRefid, invokeCircularReferenceCheck, isChecked, isReference, noChildrenAllowed, pushAndInvokeCircularReferenceCheck, setChecked, tooManyAttributes, toString`

    - ### Methods inherited from class org.apache.tools.ant.ProjectComponent

      `getDescription, getLocation, getProject, log, log, setDescription, setLocation, setProject`

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

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

- - ### Field Detail

    - #### APACHE_RESOLVER

          public static final java.lang.String APACHE_RESOLVER

      The name of the bridge to the Apache xml-commons resolver class, used to determine whether resolver.jar is present in the classpath.
      See Also:
        Constant Field Values

    - #### CATALOG_RESOLVER

          public static final java.lang.String CATALOG_RESOLVER

      Resolver base class
      See Also:
        Constant Field Values

  - ### Constructor Detail

    - #### XMLCatalog

          public XMLCatalog()

      Default constructor

  - ### Method Detail

    - #### createClasspath

          public Path createClasspath()

      Allows nested classpath elements. Not allowed if this catalog is itself a reference to another catalog -- that is, a catalog cannot both refer to another and contain elements or other attributes.
      Returns:
        a Path instance to be configured.

    - #### setClasspath

          public void setClasspath(Path classpath)

      Allows simple classpath string. Not allowed if this catalog is itself a reference to another catalog -- that is, a catalog cannot both refer to another and contain elements or other attributes.
      Parameters:
        `classpath` - the classpath to use to look up entities.

    - #### setClasspathRef

          public void setClasspathRef(Reference r)

      Allows classpath reference. Not allowed if this catalog is itself a reference to another catalog -- that is, a catalog cannot both refer to another and contain elements or other attributes.
      Parameters:
        `r` - an Ant reference containing a classpath.

    - #### createCatalogPath

          public Path createCatalogPath()

      Creates a nested `<catalogpath>` element. Not allowed if this catalog is itself a reference to another catalog -- that is, a catalog cannot both refer to another and contain elements or other attributes.
      Returns:
        a path to be configured as the catalog path.
      Throws:
        `BuildException` - if this is a reference and no nested elements are allowed.

    - #### setCatalogPathRef

          public void setCatalogPathRef(Reference r)

      Allows catalogpath reference. Not allowed if this catalog is itself a reference to another catalog -- that is, a catalog cannot both refer to another and contain elements or other attributes.
      Parameters:
        `r` - an Ant reference containing a classpath to be used as the catalog path.

    - #### getCatalogPath

          public Path getCatalogPath()

      Returns the catalog path in which to attempt to resolve DTDs.
      Returns:
        the catalog path

    - #### addDTD

          public void addDTD(ResourceLocation dtd)
                      throws BuildException

      Creates the nested `<dtd>` element. Not allowed if this catalog is itself a reference to another catalog -- that is, a catalog cannot both refer to another and contain elements or other attributes.
      Parameters:
        `dtd` - the information about the PUBLIC resource mapping to be added to the catalog
      Throws:
        `BuildException` - if this is a reference and no nested elements are allowed.

    - #### addEntity

          public void addEntity(ResourceLocation entity)
                         throws BuildException

      Creates the nested `<entity>` element. Not allowed if this catalog is itself a reference to another catalog -- that is, a catalog cannot both refer to another and contain elements or other attributes.
      Parameters:
        `entity` - the information about the URI resource mapping to be added to the catalog.
      Throws:
        `BuildException` - if this is a reference and no nested elements are allowed.

    - #### addConfiguredXMLCatalog

          public void addConfiguredXMLCatalog(XMLCatalog catalog)

      Loads a nested `<xmlcatalog>` into our definition. Not allowed if this catalog is itself a reference to another catalog -- that is, a catalog cannot both refer to another and contain elements or other attributes.
      Parameters:
        `catalog` - Nested XMLCatalog

    - #### setRefid

          public void setRefid(Reference r)
                        throws BuildException

      Makes this instance in effect a reference to another XMLCatalog instance.

      You must not set another attribute or nest elements inside this element if you make it a reference. That is, a catalog cannot both refer to another and contain elements or attributes.

      Overrides:
        `setRefid` in class `DataType`
      Parameters:
        `r` - the reference to which this catalog instance is associated
      Throws:
        `BuildException` - if this instance already has been configured.

    - #### resolveEntity

          public org.xml.sax.InputSource resolveEntity(java.lang.String publicId,
                                              java.lang.String systemId)
                                                throws org.xml.sax.SAXException,
                                                       java.io.IOException

      Implements the EntityResolver.resolveEntity() interface method.
      Specified by:
        `resolveEntity` in interface `org.xml.sax.EntityResolver`
      Parameters:
        `publicId` - the public id to resolve.
        `systemId` - the system id to resolve.
      Returns:
        the resolved entity.
      Throws:
        `org.xml.sax.SAXException` - if there is a parsing problem.
        `java.io.IOException` - if there is an IO problem.
      See Also:
        `EntityResolver.resolveEntity(java.lang.String, java.lang.String)`

    - #### resolve

          public javax.xml.transform.Source resolve(java.lang.String href,
                                           java.lang.String base)
                                             throws javax.xml.transform.TransformerException

      Implements the URIResolver.resolve() interface method.
      Specified by:
        `resolve` in interface `javax.xml.transform.URIResolver`
      Parameters:
        `href` - an href attribute.
        `base` - the base URI.
      Returns:
        a Source object, or null if href cannot be resolved.
      Throws:
        `javax.xml.transform.TransformerException` - if an error occurs.
      See Also:
        `URIResolver.resolve(java.lang.String, java.lang.String)`

    - #### dieOnCircularReference

          protected void dieOnCircularReference(java.util.Stack<java.lang.Object> stk,
                                    Project p)
                                         throws BuildException

      Description copied from class: `DataType`
      Check to see whether any DataType we hold references to is included in the Stack (which holds all DataType instances that directly or indirectly reference this instance, including this instance itself).

      If one is included, throw a BuildException created by `circularReference`.

      This implementation is appropriate only for a DataType that cannot hold other DataTypes as children.

      The general contract of this method is that it shouldn't do anything if ``checked`` is true and set it to true on exit.

      Overrides:
        `dieOnCircularReference` in class `DataType`
      Parameters:
        `stk` - the stack of references to check.
        `p` - the project to use to dereference the references.
      Throws:
        `BuildException` - on error.