Class HintHandler

  extended by org.apache.openjpa.persistence.HintHandler

public class HintHandler
extends Object

Manages query hint keys and handles their values on behalf of a owning QueryImpl. Uses specific knowledge of hint keys declared in different parts of the system. This receiver collects hint keys from different parts of the system. The keys are implicitly or explicitly declared by several different mechanics. This receiver sets the values on behalf of a owning QueryImpl based on the its specific knowledge of these keys. The hint keys from following sources are collected and handled: 1. QueryHints interface declares hint keys as public static final fields. These fields are collected by reflection. The values are handled by invoking methods on the owning QueryImpl 2. Some hint keys are collected from bean-style property names of JDBCFetchPlan by reflection and prefixed with openjpa.FetchPlan. Their values are used to set the corresponding property of FetchPlan via reflection 3. Currently defined javax.persistence.* hint keys have a equivalent counterpart to one of these FetchPlan keys. The JPA keys are mapped to equivalent FetchPlan hint keys. 4. Some keys directly invoke setters or add listeners to the owning QueryImpl. These hint keys are statically declared in this receiver itself. 5. ProductDerivation may introduce their own query hint keys via ProductDerivation.getSupportedQueryHints(). Their values are set in the FetchConfiguration.setHint(String, Object) A hint key is classified into one of the following three categories: 1. Supported: A key is known to this receiver as collected from different parts of the system. The value of a supported key is recorded and available via getHints() method. 2. Recognized: A key is not known to this receiver but has a prefix which is known to this receiver. The value of a recognized key is not recorded but its value is available via FetchConfiguration.getHint(String) 3. Unrecognized: A key is neither supported nor recognized. The value of a unrecognized key is neither recorded nor set anywhere. If an incompatible value is supplied for a supported key, a non-fatal ArgumentException is raised.

Pinaki Poddar

Field Summary
protected static Set<String> _supportedHints
protected  QueryImpl<?> owner
protected static String PREFIX_FETCHPLAN
protected static String PREFIX_JDBC
protected static String PREFIX_OPENJPA
Method Summary
 Map<String,Object> getHints()
          Gets all the recorded hint keys and their values.
 Set<String> getSupportedHints()
          Gets all the supported hint keys.
protected  boolean isKnownPrefix(String key)
          Affirms if the given key starts with any of the known prefix.
protected  Boolean record(String hint, Object value)
          Record a key-value pair only only if the given key is supported.
 void setHint(String key, Object value)
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail


protected final QueryImpl<?> owner


protected static Set<String> _supportedHints


protected static final String PREFIX_OPENJPA
See Also:
Constant Field Values


protected static final String PREFIX_JDBC
See Also:
Constant Field Values


protected static final String PREFIX_FETCHPLAN
See Also:
Constant Field Values
Method Detail


protected Boolean record(String hint,
                         Object value)
Record a key-value pair only only if the given key is supported.

FALSE if the key is unrecognized. null (i.e. MAY BE) if the key is recognized, but not supported. TRUE if the key is supported.


public void setHint(String key,
                    Object value)


protected boolean isKnownPrefix(String key)
Affirms if the given key starts with any of the known prefix.

key -


public Set<String> getSupportedHints()
Gets all the supported hint keys. The set of supported hint keys is statically determined by collecting hint keys from the ProductDerivations.


public Map<String,Object> getHints()
Gets all the recorded hint keys and their values.

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