org.rhq.enterprise.server.util

Class QueryUtility

java.lang.Object

org.rhq.enterprise.server.util.QueryUtility

public class QueryUtility
extends Object

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	QueryUtility.PagedDataFetchSettings A settings object for the fetchPagedDataAndCount(javax.persistence.Query, javax.persistence.Query, org.rhq.core.domain.util.PageControl, org.rhq.enterprise.server.util.QueryUtility.PagedDataFetchSettings) method.

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_PHANTOM_READ_MAX_ATTEMPTS Default value for PHANTOM_READ_MAX_ATTEMPTS.
static int	DEFAULT_PHANTOM_READ_MAX_WAIT_TIME Default value for PHANTOM_READ_MAX_WAIT_TIME.
static int	DEFAULT_PHANTOM_READ_MIN_WAIT_TIME Default value for PHANTOM_READ_MIN_WAIT_TIME.
static int	PHANTOM_READ_MAX_ATTEMPTS The maximum number of retries the fetchPagedDataAndCount(javax.persistence.Query, javax.persistence.Query, org.rhq.core.domain.util.PageControl, org.rhq.enterprise.server.util.QueryUtility.PagedDataFetchSettings) method tries to get consistent results.
static int	PHANTOM_READ_MAX_WAIT_TIME The maximum wait time between retries in the fetchPagedDataAndCount(javax.persistence.Query, javax.persistence.Query, org.rhq.core.domain.util.PageControl, org.rhq.enterprise.server.util.QueryUtility.PagedDataFetchSettings) method when trying to get consistent results.
static int	PHANTOM_READ_MIN_WAIT_TIME The minimum wait time between retries in the fetchPagedDataAndCount(javax.persistence.Query, javax.persistence.Query, org.rhq.core.domain.util.PageControl, org.rhq.enterprise.server.util.QueryUtility.PagedDataFetchSettings) method when trying to get consistent results.

Constructor Summary

Constructors

Constructor and Description
QueryUtility()

Method Summary

Methods

Modifier and Type	Method and Description
static String	escapeSearchParameter(String value) Given the settings for the current DatabaseType, properly handle escaping special SQL characters.
static <T> org.rhq.core.domain.util.PageList<T>	fetchPagedDataAndCount(javax.persistence.Query dataQuery, javax.persistence.Query countQuery, org.rhq.core.domain.util.PageControl pageControl, QueryUtility.PagedDataFetchSettings settings) Fetches the data and the total count using the provided queries, according to the provided pageControl object.
static String	formatSearchParameter(String value) Given the settings for the current DatabaseType, properly handle escaping special SQL characters as well as UPCASING the value (standard for rhq filter searches) and wrapping with SQL wildcard for implicit "contains" (i.e.
static String	getEscapeCharacter() Get the proper ESCAPE clause character for the current DatabaseType.
static String	getEscapeClause() Get the proper LIKE operator escape clause for the current DatabaseType.
static String	getEscapeClauseCharacter() Get the proper ESCAPE clause character for the current DatabaseType.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_PHANTOM_READ_MAX_ATTEMPTS

public static final int DEFAULT_PHANTOM_READ_MAX_ATTEMPTS

Default value for PHANTOM_READ_MAX_ATTEMPTS.

See Also:

Constant Field Values

DEFAULT_PHANTOM_READ_MIN_WAIT_TIME

public static final int DEFAULT_PHANTOM_READ_MIN_WAIT_TIME

Default value for PHANTOM_READ_MIN_WAIT_TIME.

See Also:

Constant Field Values

DEFAULT_PHANTOM_READ_MAX_WAIT_TIME

public static final int DEFAULT_PHANTOM_READ_MAX_WAIT_TIME

Default value for PHANTOM_READ_MAX_WAIT_TIME.

See Also:

Constant Field Values

PHANTOM_READ_MAX_ATTEMPTS

public static final int PHANTOM_READ_MAX_ATTEMPTS

The maximum number of retries the fetchPagedDataAndCount(javax.persistence.Query, javax.persistence.Query, org.rhq.core.domain.util.PageControl, org.rhq.enterprise.server.util.QueryUtility.PagedDataFetchSettings) method tries to get consistent results.

Inconsistent results may be caused by a phantom read in the database between performing the data and total count queries.

PHANTOM_READ_MIN_WAIT_TIME

public static final int PHANTOM_READ_MIN_WAIT_TIME

The minimum wait time between retries in the fetchPagedDataAndCount(javax.persistence.Query, javax.persistence.Query, org.rhq.core.domain.util.PageControl, org.rhq.enterprise.server.util.QueryUtility.PagedDataFetchSettings) method when trying to get consistent results. The wait time gradually increases in a geometric progression from this value to the PHANTOM_READ_MAX_WAIT_TIME over PHANTOM_READ_MAX_ATTEMPTS.

Inconsistent results may be caused by a phantom read in the database between performing the data and total count queries.

PHANTOM_READ_MAX_WAIT_TIME

public static final int PHANTOM_READ_MAX_WAIT_TIME

The maximum wait time between retries in the fetchPagedDataAndCount(javax.persistence.Query, javax.persistence.Query, org.rhq.core.domain.util.PageControl, org.rhq.enterprise.server.util.QueryUtility.PagedDataFetchSettings) method when trying to get consistent results. The wait time gradually increases in a geometric progression from PHANTOM_READ_MIN_WAIT_TIME to this value over PHANTOM_READ_MAX_ATTEMPTS.

Inconsistent results may be caused by a phantom read in the database between performing the data and total count queries.

Constructor Detail

QueryUtility

public QueryUtility()

Method Detail

fetchPagedDataAndCount

public static <T> org.rhq.core.domain.util.PageList<T> fetchPagedDataAndCount(javax.persistence.Query dataQuery,
                                                              javax.persistence.Query countQuery,
                                                              org.rhq.core.domain.util.PageControl pageControl,
                                                              QueryUtility.PagedDataFetchSettings settings)
                                                                   throws PhantomReadMaxAttemptsExceededException

Fetches the data and the total count using the provided queries, according to the provided pageControl object.

The fetch can be set up to try and avoid phantom reads - i.e. the possible inconsistencies between the number of results, the obtained total count and the page control objects.

Type Parameters:

T - the type of the result entities

Parameters:

dataQuery - the query to use to fetch the data. The provided pageControl is used to set the paging on this query.

countQuery - the query to use to obtain the total number of results

pageControl - the object to control the paging of the results

settings - the optional settings of the fetching. If null is passed, the behavior is the same as if a "default" instance of the QueryUtility.PagedDataFetchSettings was passed.

Returns:

the page list containing the page of the data, total count and page control

Throws:

PhantomReadMaxAttemptsExceededException - if the settings specified to throw an exception on exceeding the number of attempts to avoid phantom read

See Also:

PageControl.isConsistentWith(java.util.Collection, int)

escapeSearchParameter

public static String escapeSearchParameter(String value)

Given the settings for the current DatabaseType, properly handle escaping special SQL characters.

Parameters:

value -

Returns:

the properly escaped value.

formatSearchParameter

public static String formatSearchParameter(String value)

Given the settings for the current DatabaseType, properly handle escaping special SQL characters as well as UPCASING the value (standard for rhq filter searches) and wrapping with SQL wildcard for implicit "contains" (i.e. '%' characters)

Parameters:

value -

Returns:

the properly escaped and formatted value.

getEscapeClause

public static String getEscapeClause()

Get the proper LIKE operator escape clause for the current DatabaseType.

Returns:

The escape clause buffered with single spaces. For example: " ESCAPE '\' "

getEscapeClauseCharacter

public static String getEscapeClauseCharacter()

Get the proper ESCAPE clause character for the current DatabaseType. This is for use when constructing query strings to be parsed (it may itself escape the escape character for proper parsing (like in Postgres when standard_conforming_strings is off). Call getEscapeCharacterParam() when needed for setting a NamedQuery parameter.

Returns:

The escape character as a String. The string may actually be multiple character but when parsed by the vendor it will parse out the single character.

getEscapeCharacter

public static String getEscapeCharacter()

Get the proper ESCAPE clause character for the current DatabaseType. This is for use when setting a NamedQuery paramater (unparsed, guaranteed to be a single char). If constructing query strings to be parsed Call getEscapeCharacter()

Returns:

The single escape character as a String.