org.apache.sis.metadata.sql

Class MetadataSource

Object

MetadataSource

All Implemented Interfaces:

AutoCloseable

Direct Known Subclasses:

MetadataWriter

public class MetadataSource
extends Object
implements AutoCloseable

A connection to a metadata database in read-only mode. It can be either the database provided by Apache SIS with pre-defined ISO 19115 metadata, or another database specified at construction time. Metadata instances can be obtained as in the example below:

MetadataSource metadata = MetadataSource.getProvided();
Format format = source.lookup(Format.class, "PNG");

where id is the primary key value for the desired record in the MD_Format table.

Properties

The constructor expects three Java arguments (the metadata standard, the data source and the database schema) completed by an arbitrary amount of optional arguments given as a map of properties. The following keys are recognized by Metadata­Source and all other entries are ignored:

Optional properties at construction time

Key	Value type	Description
"catalog"	String	The database catalog where the metadata schema is stored.
"classloader"	ClassLoader	The class loader to use for creating Proxy instances.
"maxStatements"	Integer	Maximal number of Prepared­Statements that can be kept simultaneously open.

Concurrency

Metadata­Source is thread-safe but is not concurrent. If concurrency is desired, multiple instances of Metadata­Source can be created for the same Data­Source. The Metadata­Source(Metadata­Source) convenience constructor can be used for this purpose.

Since:

0.8

Defined in the sis-metadata module

Field Summary

Fields

Modifier and Type	Field and Description
protected MetadataStandard	standard The metadata standard to be used for constructing the database schema.

Constructor Summary

Constructors

Constructor and Description
MetadataSource(MetadataSource source) Creates a new metadata source with the same configuration than the given source.
MetadataSource(MetadataStandard standard, DataSource dataSource, String schema, Map<String,?> properties) Creates a new metadata source.

Method Summary

Modifier and Type	Method and Description
void	addWarningListener(WarningListener<? super MetadataSource> listener) Adds a listener to be notified when a warning occurred while reading from or writing metadata.
void	close() Closes the database connection used by this object.
static MetadataSource	getProvided() Returns the metadata source connected to the "jdbc/Spatial­Metadata" database.
<T> T	lookup(Class<T> type, String identifier) Returns an implementation of the specified metadata interface filled with the data referenced by the specified identifier.
void	removeWarningListener(WarningListener<? super MetadataSource> listener) Removes a previously registered listener.
String	search(Object metadata) Searches for the given metadata in the database.

Methods inherited from class Object

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

Field Detail

standard

protected final MetadataStandard standard

The metadata standard to be used for constructing the database schema.

Constructor Detail

MetadataSource

public MetadataSource(MetadataStandard standard,
                      DataSource dataSource,
                      String schema,
                      Map<String,?> properties)

Creates a new metadata source. The metadata standard to implement (typically ISO 19115, but not necessarily) and the database source are mandatory information. All other information are optional and can be null.

Parameters:

standard - the metadata standard to implement.

data­Source - the source for getting a connection to the database.

schema - the database schema were metadata tables are stored, or null if none.

properties - additional options, or null if none. See class javadoc for a description.

MetadataSource

public MetadataSource(MetadataSource source)

Creates a new metadata source with the same configuration than the given source. The two Metadata­Source instances will share the same Data­Source but will use their own Connection. This constructor is useful when concurrency is desired.

The new Metadata­Source initially contains all warning listeners declared in the given source. But listeners added or removed in a Metadata­Source after the construction will not impact the other Metadata­Source instance.

Parameters:

source - the source from which to copy the configuration.

Method Detail

getProvided

public static MetadataSource getProvided()
                                  throws MetadataStoreException

Returns the metadata source connected to the "jdbc/Spatial­Metadata" database. In a default Apache SIS installation, this metadata source contains pre-defined records for some commonly used citations and formats among others.

Returns:

source of pre-defined metadata records from the "jdbc/Spatial­Metadata" database.

Throws:

Metadata­Store­Exception - if this method can not connect to the database.

search

public String search(Object metadata)
              throws MetadataStoreException

Searches for the given metadata in the database. If such metadata is found, then its identifier (primary key) is returned. Otherwise this method returns null.

Parameters:

metadata - the metadata to search for.

Returns:

the identifier of the given metadata, or null if none.

Throws:

Metadata­Store­Exception - if the metadata object does not implement a metadata interface of the expected package, or if an error occurred while searching in the database.

lookup

public <T> T lookup(Class<T> type,
                    String identifier)
             throws MetadataStoreException

Returns an implementation of the specified metadata interface filled with the data referenced by the specified identifier. Alternatively, this method can also return a Code­List or Enum element.

Type Parameters:

T - the parameterized type of the type argument.

Parameters:

type - the interface to implement (e.g. Citation), or the Controlled­Vocabulary type (Code­List or some Enum).

identifier - the identifier of the record for the metadata entity to be created. This is usually the primary key of the record to search for.

Returns:

an implementation of the required interface, or the code list element.

Throws:

Metadata­Store­Exception - if a SQL query failed.

addWarningListener

public void addWarningListener(WarningListener<? super MetadataSource> listener)
                        throws IllegalArgumentException

Adds a listener to be notified when a warning occurred while reading from or writing metadata. When a warning occurs, there is a choice:

• If this metadata source has no warning listener, then the warning is logged at Level.WARNING.
• If this metadata source has at least one warning listener, then all listeners are notified and the warning is not logged by this metadata source instance.

Consider invoking this method in a try … finally block if the Metadata­Source lifetime is longer than the listener lifetime, as below:

source.addWarningListener(listener);
try {
    // Do some work...
} finally {
    source.removeWarningListener(listener);
}

Parameters:

listener - the listener to add.

Throws:

Illegal­Argument­Exception - if the given listener is already registered in this metadata source.

removeWarningListener

public void removeWarningListener(WarningListener<? super MetadataSource> listener)
                           throws NoSuchElementException

Removes a previously registered listener.

Parameters:

listener - the listener to remove.

Throws:

No­Such­Element­Exception - if the given listener is not registered in this metadata source.

close

public void close()
           throws MetadataStoreException

Closes the database connection used by this object.

Specified by:

close in interface Auto­Closeable

Throws:

Metadata­Store­Exception - if an error occurred while closing the connection.