org.objectweb.cjdbc.controller.cache.metadata.MetadataCache Class Reference

List of all members.

Public Member Functions
	MetadataCache (int maxNbOfMetadata, int maxNbOfField)
Field[]	getMetadata (AbstractRequest request)
void	addMetadata (AbstractRequest request, Field[] metadata)
Field	getField (String fullyQualifiedFieldName)
void	addField (String fullyQualifiedFieldName, Field field)
String	getXml ()

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Detailed Description

This class implements a ResultSet metadata cache.

ResultSet Fields are kept here to prevent recomputing them and allocating them each time a query is executed.

Author:

Emmanuel Cecchet

Version:

1.0

Definition at line 44 of file MetadataCache.java.

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Constructor & Destructor Documentation

org.objectweb.cjdbc.controller.cache.metadata.MetadataCache.MetadataCache (  int  maxNbOfMetadata, int  maxNbOfField )

Constructor for MetadataCache. Parameters: maxNbOfMetadata  maximum nb of entries in metadata cache maxNbOfField  maximum nb of entries in field cache Definition at line 58 of file MetadataCache.java. { metadataCache = new Hashtable(maxNbOfMetadata == 0 ? 10000 : maxNbOfMetadata); fieldCache = new Hashtable(maxNbOfField == 0 ? 100 : maxNbOfField); if (maxNbOfMetadata < 0) throw new RuntimeException(Translate.get("cache.metadata.invalid.size", maxNbOfMetadata)); if (maxNbOfMetadata == 0) this.maxNbOfMetadata = Integer.MAX_VALUE; else this.maxNbOfMetadata = maxNbOfMetadata; if (maxNbOfField < 0) throw new RuntimeException(Translate.get("cache.metadata.invalid.size", maxNbOfField)); if (maxNbOfField == 0) this.maxNbOfField = Integer.MAX_VALUE; else this.maxNbOfField = maxNbOfField; }

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Member Function Documentation

void org.objectweb.cjdbc.controller.cache.metadata.MetadataCache.addField (  String  fullyQualifiedFieldName, Field  field )

Add a Field entry to the cache and associate it to the given name. Parameters: fullyQualifiedFieldName  table.column name that uniquely identifies the field field  field to cache Definition at line 167 of file MetadataCache.java. { // Note that the underlying cache Hashtable is synchronized and we usually // do not need to synchronize on it. // As we will have to add a cache entry, check if the cache size is ok // else remove the first entry of the hashtable. while (fieldCache.size() > maxNbOfField) { // Remove first entry from Hashtable. We need to synchronize here to be // sure that we are not trying to concurrently remove the first cache // entry. synchronized (fieldCache) { try { fieldCache.remove(fieldCache.keys().nextElement()); } catch (Exception ignore) { break; } } } // Add to cache try { fieldCache.put(fullyQualifiedFieldName, field); } catch (OutOfMemoryError oome) { synchronized (fieldCache) { fieldCache.clear(); } System.gc(); logger.warn(Translate.get("cache.memory.error.cache.flushed", this .getClass())); } }

void org.objectweb.cjdbc.controller.cache.metadata.MetadataCache.addMetadata (  AbstractRequest  request, Field[]  metadata )

Add a metadata entry to the cache and associate it to the given request. Parameters: request  request to which the metadata belong metadata  metadata to cache Definition at line 103 of file MetadataCache.java. References org.objectweb.cjdbc.common.sql.AbstractRequest.getSQL(), and org.objectweb.cjdbc.common.sql.AbstractRequest.getSqlSkeleton(). { // Note that the underlying cache Hashtable is synchronized and we usually // do not need to synchronize on it. // As we will have to add a cache entry, check if the cache size is ok // else remove the first entry of the hashtable. while (metadataCache.size() > maxNbOfMetadata) { // Remove first entry from Hashtable. We need to synchronize here to be // sure that we are not trying to concurrently remove the first cache // entry. synchronized (metadataCache) { try { metadataCache.remove(metadataCache.keys().nextElement()); } catch (Exception ignore) { break; } } } // Add to cache try { String sqlSkeleton = request.getSqlSkeleton(); if (sqlSkeleton != null) metadataCache.put(sqlSkeleton, metadata); else metadataCache.put(request.getSQL(), metadata); } catch (OutOfMemoryError oome) { synchronized (metadataCache) { metadataCache.clear(); } System.gc(); logger.warn(Translate.get("cache.memory.error.cache.flushed", this .getClass())); } }

Field org.objectweb.cjdbc.controller.cache.metadata.MetadataCache.getField (  String  fullyQualifiedFieldName  )

Get the field corresponding to a column name. Returns null if the cache contains no field for the given name. Parameters: fullyQualifiedFieldName  the field name (table.column) to look for Returns: the corresponding Field or null if not in cache Definition at line 155 of file MetadataCache.java. { return (Field) fieldCache.get(fullyQualifiedFieldName); }

Field [] org.objectweb.cjdbc.controller.cache.metadata.MetadataCache.getMetadata (  AbstractRequest  request  )

Get metadata associated to a request. Returns null if the cache contains no metadata for the given request. Parameters: request  the request we look for Returns: the metadata or null if not in cache Definition at line 88 of file MetadataCache.java. References org.objectweb.cjdbc.common.sql.AbstractRequest.getSQL(), and org.objectweb.cjdbc.common.sql.AbstractRequest.getSqlSkeleton(). { String sqlSkeleton = request.getSqlSkeleton(); if (sqlSkeleton != null) return (Field[]) metadataCache.get(sqlSkeleton); else return (Field[]) metadataCache.get(request.getSQL()); }

String org.objectweb.cjdbc.controller.cache.metadata.MetadataCache.getXml (   )

Get xml information about this ParsingCache Returns: String in xml formatted text Definition at line 211 of file MetadataCache.java. { return "<" + DatabasesXmlTags.ELT_MetadataCache + " " + DatabasesXmlTags.ATT_maxNbOfMetadata + "=\"" + maxNbOfMetadata + "\" " + DatabasesXmlTags.ATT_maxNbOfField + "=\"" + (maxNbOfField == Integer.MAX_VALUE ? 0 : maxNbOfField) + "\"/>"; }

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The documentation for this class was generated from the following file:

• MetadataCache.java

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