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Oracle® OLAP Java API Developer's Guide
11g Release 2 (11.2)
E10795-03
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3 Discovering Metadata

This chapter describes how to connect to an Oracle Database instance and how to discover existing Oracle OLAP metadata objects. It includes the following topics:

Connecting to Oracle OLAP

To connect to the Oracle OLAP server in an Oracle Database instance, an OLAP Java API client application uses the Oracle implementation of the Java Database Connectivity (JDBC) API. The Oracle JDBC classes that you use to establish a connection to Oracle OLAP are in the Java archive file ojdbc5.jar. For information about getting that file, see Appendix A, "Setting Up the Development Environment".

Prerequisites for Connecting

Before attempting to connect to the Oracle OLAP server, ensure that the following requirements are met:

  • The Oracle Database instance is running and was installed with the OLAP option.

  • The Oracle Database user ID that you are using for the connection has access to the relational schemas that contain the data.

  • The Oracle JDBC and OLAP Java API jar files are in your application development environment. For information about setting up the required jar files, see Appendix A, "Setting Up the Development Environment".

Establishing a Connection

To connect to the OLAP server, perform the following steps:

  1. Create a JDBC connection to the database.

  2. Create a DataProvider and a UserSession.

These steps are explained in more detail in the rest of this topic.

Creating a JDBC Connection

One way to create a connection to an Oracle Database instance is to use oracle.jdbc.OracleDataSource and oracle.jdbc.OracleConnection objects. For example, the following code creates an oracle.jdbc.OracleDataSource, sets properties of the object, and then gets a JDBC OracleConnection object from the OracleDataSource.

The values of the properties for the OracleDataSource are from a java.util.Properties object. The url property has the form jdbc:oracle:thin:@serverName:portNumber:sid, where serverName is the hostname of the server on which the Oracle Database instance is running, portNumber is the number of the TCP/IP listener port for the database, and sid is the system identifier (SID) of the database instance.

Example 3-1 Getting a JDBC OracleConnection

oracle.jdbc.OracleConnection conn = null;
try 
{
  OracleDataSource ods = new OracleDataSource();
  ods.setURL(props.getProperty("url"));
  ods.setUser(props.getProperty("user"));
  ods.setPassword(props.getProperty("password"));
  conn = (oracle.jdbc.OracleConnection) ods.getConnection();
}
catch(SQLException e) 
{
  System.out.println("Connection attempt failed. " + e);
}

In the example, the connection uses the Oracle JDBC thin driver. There are many ways to specify your connection characteristics using the getConnection method. There are also other ways to connect to an Oracle Database instance. For more information about Oracle JDBC connections, see Oracle Database JDBC Developer's Guide.

After you have the OracleConnection object, you can create OLAP Java API DataProvider and UserSession objects.

Creating a DataProvider and a UserSession

The following code creates a DataProvider and a UserSession. The conn object is the OracleConnection from Example 3-1.

Example 3-2 Creating a DataProvider

DataProvider dp = new DataProvider();
try
{
  UserSession session = dp.createSession(conn);
}
catch(SQLException e)
{
  System.out.println("Could not create a UserSession. " + e);
}

Using the DataProvider, you can get the MdmMetadataProvider, which is described in "Creating an MdmMetadataProvider". You use the DataProvider to get the TransactionProvider and to create Source and CursorManager objects as described in Chapter 5, "Understanding Source Objects" and Chapter 6, "Making Queries Using Source Methods".

Closing the Connection and the DataProvider

If you are finished using the OLAP Java API, but you want to continue working in your JDBC connection to the database, then use the close method of your DataProvider to release the OLAP Java API resources.

dp.close();     // dp is the DataProvider

When you have completed your work with the database, use the OracleConnection.close method.

Example 3-3 Closing the Connection

try
{
  conn.close();     // conn is the OracleConnection
}
catch(SQLException e) 
{
  System.out.println("Cannot close the connection. " + e);
}

Overview of the Procedure for Discovering Metadata

The OLAP Java API provides access to the data of an analytic workspace or that is in relational structures. This collection of data is the data store for the application.

Potentially, the data store includes all of the subchemas of the MdmRootSchema. However, the scope of the data store that is visible when an application is running depends on the database privileges that apply to the user ID through which the connection was made. A user can see all of the MdmDatabaseSchema objects that exist under the MdmRootSchema, but the user can see the objects that are owned by an MdmDatabaseSchema only if the user has access rights to the metadata objects. For information on granting access rights and on object security, see Oracle OLAP User's Guide.

Purpose of Discovering the Metadata

The metadata objects in the data store help your application to make sense of the data. They provide a way for you to find out what data is available, how it is structured, and what the characteristics of it are.

Therefore, after connecting, your first step is to find out what metadata is available. You can then present choices to the end user about what data to select or calculate and how to display it.

After an application discovers the metadata, it typically goes on to create queries for selecting, calculating, and otherwise manipulating the data. To work with data in these ways, you must get the Source objects from the metadata objects. These Source objects specify the data for querying. For more information on Source objects, see Chapter 5, "Understanding Source Objects".

Steps in Discovering the Metadata

Before investigating the metadata, your application must make a connection to Oracle OLAP. Then, your application might perform the following steps:

  1. Create a DataProvider.

  2. Get the MdmMetadataProvider from the DataProvider.

  3. Get the MdmRootSchema from the MdmMetadataProvider.

  4. Get all of the MdmDatabaseSchema objects or get individual ones.

  5. Get the MdmCube, MdmDimension, and MdmOrganizationalSchema objects owned by the MdmDatabaseSchema objects.

The next four topics in this chapter describe these steps in detail.

Creating an MdmMetadataProvider

An MdmMetadataProvider gives access to the metadata in a data store by providing the MdmRootSchema. Before you can create an MdmMetadataProvider, you must create a DataProvider as described in Chapter 4, "Creating Metadata and Analytic Workspaces". Example 3-4 creates an MdmMetadataProvider. In the example, dp is the DataProvider.

Example 3-4 Creating an MdmMetadataProvider

MdmMetadataProvider mp = null;
try
{
  mp = (MdmMetadataProvider) dp.getMdmMetadataProvider();
}
catch (Exception e) 
{
  println("Cannot get the MDM metadata provider. " + e);
}

Getting the MdmSchema Objects

The Oracle OLAP metadata objects that provide access to the data in a data store are organized by MdmSchema objects. The top-level MdmSchema is the MdmRootSchema. Getting the MdmRootSchema is the first step in exploring the metadata in your data store. From the MdmRootSchema, you can get the MdmDatabaseSchema objects. The MdmRootSchema has an MdmDatabaseSchema for each database user. An MdmDatabaseSchema can have MdmOrganizationalSchema objects that organize the metadata objects owned by the MdmDatabaseSchema.

Example 3-5 demonstrates getting the MdmRootSchema, the MdmDatabaseSchema objects under it, and any MdmOrganizationalSchema objects under them.

Example 3-5 Getting the MdmSchema Objects

private void getSchemas(MdmMetadataProvider mp)
{
  MdmRootSchema mdmRootSchema = (MdmRootSchema)mp.getRootSchema();
  List<MdmDatabaseSchema> dbSchemas = mdmRootSchema.getDatabaseSchemas();
  for(MdmDatabaseSchema mdmDBSchema : dbSchemas)
  {
    println(mdmDBSchema.getName());
    getOrgSchemas(mdmDBSchema);
  } 
}

private void getOrgSchemas(MdmSchema mdmSchema)
{
  ArrayList orgSchemaList = new ArrayList();

  if (mdmSchema instanceof MdmDatabaseSchema)
  {
    MdmDatabaseSchema mdmDBSchema = (MdmDatabaseSchema) mdmSchema;
    orgSchemaList = (ArrayList) mdmDBSchema.getOrganizationalSchemas();
  }
  else if (mdmSchema instanceof MdmOrganizationalSchema)
  {
    MdmOrganizationalSchema mdmOrgSchema = (MdmOrganizationalSchema) 
                                            mdmSchema;
    orgSchemaList = (ArrayList) mdmOrgSchema.getOrganizationalSchemas();
  }

  if (orgSchemaList.size() > 0)
  {
    println("The MdmOrganizationalSchema subschemas of "
            + mdmSchema.getName() + " are:");
    Iterator orgSchemaListItr = orgSchemaList.iterator();
    while (orgSchemaListItr.hasNext())
    {
      MdmOrganizationalSchema mdmOrgSchema = (MdmOrganizationalSchema)
                                            orgSchemaListItr.next();
      println(mdmOrgSchema.getName());
      getOrgSchemas(mdmOrgSchema);
    }
  }
  else
  {
    println(mdmSchema.getName() + " does not have any" +
            " MdmOrganizationalSchema subschemas.");
  }
}

Rather than getting all of the MdmDatabaseSchema objects, you can use the getDatabaseSchema method of the MdmRootSchema to get the schema for an individual user. Example Example 3-6 demonstrates getting the MdmDatabaseSchema for the GLOBAL user.

Example 3-6 Getting a Single MdmDatabaseSchema

MdmDatabaseSchema mdmGlobalSchema = mdmRootSchema.getDatabaseSchema("GLOBAL");

Getting the Contents of an MdmSchema

From an MdmSchema, you can get all of the subschema, MdmCube, MdmPrimaryDimension, and MdmMeasure objects that it contains. Also, the MdmRootSchema has an MdmMeasureDimension that has a List of all of the available MdmMeasure objects.

If you want to display all of the dimensions and methods that are owned by a particular user, then you could get the lists of dimensions and measures from the MdmDatabaseSchema for that user. Example 3-7 gets the dimensions and measures from the MdmDatabaseSchema from Example 3-6. It displays the name of each dimension and measure.

Example 3-7 Getting the Dimensions and Measures of an MdmDatabaseSchema

private void getObjects(MdmDatabaseSchema mdmGlobalSchema)
{
  List dimList = mdmGlobalSchema.getDimensions();
  String objName = mdmGlobalSchema.getName() + " schema";
  getNames(dimList, "dimensions", objName);

  List measList = mdmGlobalSchema.getMeasures();
  getNames(measList, "measures", objName);
}

private void getNames(List objectList, String objTypes, String objName)
{
  println("The " + objTypes + " of the " + objName + " are:");
  Iterator objListItr = objectList.iterator();
  while (objListItr.hasNext())
  {
    MdmObject mdmObj = (MdmObject) objListItr.next();
    println(mdmObj.getName());
  }
}

The output of Example 3-7 is the following.

The dimensions of the GLOBAL schema are:
CHANNEL_AWJ
CUSTOMER_AWJ
PRODUCT_AWJ
TIME_AWJ
The measures of the GLOBAL schema are:
UNIT_COST
UNIT_PRICE
SALES
UNITS
COST

To display just the dimensions and measures associated with an MdmCube, you could use the findOrCreateCube method of an MdmDatabaseSchema to get the cube and then get the dimensions and measures of the cube. Example 3-8 gets an MdmCube from the MdmDatabaseSchema of Example 3-6 and displays the names of the dimensions and measures associated with it using the getNames method of Example 3-7.

Example 3-8 Getting the Dimensions and Measures of an MdmCube

private void getCubeObjects(MdmDatabaseSchema mdmGlobalSchema)
{
  MdmCube mdmUnitsCube = (MdmCube)
    mdmGlobalSchema.findOrCreateCube("PRICE_CUBE_AWJ");
  String objName = mdmUnitsCube.getName() + " cube";
  List dimList = mdmUnitsCube.getDimensions();
  getNames(dimList, "dimensions", objName);

  List<MdmMeasure> measList = mdmUnitsCube.getMeasures();
  getNames(measList, "measures", objName);
}

The output of Example 3-8 is the following.

The dimensions of the PRICE_CUBE_AWJ cube are:
TIME_AWJ
PRODUCT_AWJ
The measures of the PRICE_CUBE_AWJ cube are:
UNIT_COST
UNIT_PRICE

Getting the Objects Contained by an MdmPrimaryDimension

In discovering the metadata objects to use in creating queries and displaying the data, an application typically gets the MdmSubDimension components of an MdmPrimaryDimension and the MdmAttribute objects that are associated with the dimension. This topic demonstrates getting the components and attributes of a dimension.

Getting the Hierarchies and Levels of an MdmPrimaryDimension

An MdmPrimaryDimension has zero or more component MdmHierarchy objects, which you can obtain by calling the getHierarchies method of the dimension. That method returns a List of MdmHierarchy objects. The levels of an MdmPrimaryDimension are represented by MdmDimensionLevel objects.

If an MdmHierarchy is an MdmLevelHierarchy, then it has MdmHierarchyLevel objects that associate MdmDimensionLevel objects with it. You can obtain the MdmHierarchyLevel objects by calling the getHierarchyLevels method of the MdmLevelHierarchy.

Example 3-9 gets an MdmPrimaryDimension from the MdmDatabaseSchema of Example 3-6 and displays the names of the hierarchies and the levels associated with them.

Example 3-9 Getting the Hierarchies and Levels of a Dimension

private void getHierarchiesAndLevels(MdmDatabaseSchema mdmGlobalSchema)
{
  MdmPrimaryDimension mdmCustDim = (MdmPrimaryDimension)
    mdmGlobalSchema.findOrCreateStandardDimension("CUSTOMER_AWJ");
  List<MdmHierarchy> hierList = mdmCustDim.getHierarchies();
  println("The hierarchies of the dimension are:");
  for (MdmHierarchy mdmHier : hierList)
  {
    println(mdmHier.getName());
    if (mdmHier instanceof MdmLevelHierarchy)
    {
      MdmLevelHierarchy mdmLevelHier = (MdmLevelHierarchy) mdmHier; 
      List<MdmHierarchyLevel> hierLevelList = mdmLevelHier.getHierarchyLevels();
      println("  The levels of the hierarchy are:");
      for (MdmHierarchyLevel mdmHierLevel : hierLevelList)
      {
        println("  " + mdmHierLevel.getName());
      }
    }
  }
}

The output of Example 3-9 is the following.

The hierarchies of the dimension are:
SHIPMENTS
  The levels of the hierarchy are:
  TOTAL_CUSTOMER
  REGION
  WAREHOUSE
  SHIP_TO
MARKETS
  The levels of the hierarchy are:
  TOTAL_MARKET
  MARKET_SEGMENT
  ACCOUNT
  SHIP_TO

Getting the Attributes for an MdmPrimaryDimension

An MdmPrimaryDimension and the hierarchies and levels of it have associated MdmAttribute objects. You can obtain many of the attributes by calling the getAttributes method of the dimension, hierarchy, or level. That method returns a List of MdmAttribute objects that an application has explicitly added to or specified for the MdmPrimaryDimension. You can obtain specific attributes, such as a short or long description attribute or a parent attribute by calling the appropriate method of an MdmPrimaryDimension or an MdmHierarchy.

Example 3-10 demonstrates getting the MdmAttribute objects for an MdmPrimaryDimension. It also gets the parent attribute separately. The example displays the names of the MdmAttribute objects. The attribute names that end in _LD and _SD are the attributes that are added to the MdmHierarchyLevel objects, as mentioned in "Populating OLAP Views with Hierarchical Attribute Values".

Example 3-10 Getting the MdmAttribute Objects of an MdmPrimaryDimension

private void getAttributes(MdmDatabaseSchema mdmGlobalSchema)
{
  MdmTimeDimension mdmTimeDim = (MdmTimeDimension)
    mdmGlobalSchema.findOrCreateTimeDimension("TIME_AWJ");
  List attrList = mdmTimeDim.getAttributes();
  Iterator attrListItr = attrList.iterator();
  println("The MdmAttribute objects of " + mdmTimeDim.getName() + " are:");
  while (attrListItr.hasNext()) 
  {
    MdmAttribute mdmAttr = (MdmAttribute) attrListItr.next();
    println("  " + mdmAttr.getName());
  }

  MdmAttribute mdmParentAttr = mdmTimeDim.getParentAttribute();
  println("The parent attribute is " + mdmParentAttr.getName() + ".");
}

The output of Example 3-10 is the following.

The MdmAttribute objects of TIME_AWJ are:
 LONG_DESCRIPTION
 SHORT_DESCRIPTION
 END_DATE
 TIME_SPAN
 TOTAL_TIME_LD
 YEAR_LD
 QUARTER_LD
 MONTH_LD
 TOTAL_TIME_SD
 YEAR_SD
 QUARTER_SD
 MONTH_SD
 TOTAL_TIME_ED
 YEAR_ED
 QUARTER_ED
 MONTH_ED
 TOTAL_TIME_TS
 YEAR_TS
 QUARTER_TS
 MONTH_TS
The parent attribute is PARENT_ATTRIBUTE.

Getting the Source for a Metadata Object

A metadata object represents a set of data, but it does not provide the ability to create queries on that data. The object is informational. It records the existence, structure, and characteristics of the data. It does not give access to the data values.

To access the data values for a metadata object, an application gets the Source object for that metadata object. The Source for a metadata object is a primary Source.

To get the primary Source for a metadata object, an application calls the getSource method of that metadata object. For example, if an application needs to display the quantity of product units sold during the year 1999, then it must use the getSource method of the MdmMeasure for that data, which is mdmUnits in the following example.

Example 3-11 Getting a Primary Source for a Metadata Object

Source units = mdmUnits.getSource();

For more information about getting and working with primary Source objects, see Chapter 5, "Understanding Source Objects".