org.datanucleus.store.rdbms.sql.expression

Class ExpressionUtils

java.lang.Object

org.datanucleus.store.rdbms.sql.expression.ExpressionUtils

public class ExpressionUtils
extends Object

Utility methods for working with SQL expressions.

Constructor Summary

Constructors

Constructor and Description
ExpressionUtils()

Method Summary

Modifier and Type	Method and Description
static void	checkAndCorrectExpressionMappingsForBooleanComparison(SQLExpression expr1, SQLExpression expr2) Convenience method that compares the mappings used by the two expressions for compatibility for use in a boolean comparison (eq, noteq, gt, gteq, lt, lteq) and, if necessary, updates the mapping if one of them is a SQLLiteral and is deemed inconsistent with the other expression.
protected static void	checkAndCorrectLiteralForConsistentMappingsForBooleanComparison(SQLLiteral lit, SQLExpression expr)
static BooleanExpression	getAppIdEqualityExpression(Object id, SQLExpression expr, RDBMSStoreManager storeMgr, org.datanucleus.ClassLoaderResolver clr, org.datanucleus.metadata.AbstractClassMetaData acmd, Integer index, BooleanExpression bExpr) Create an equality expression "(expr == id)" for an application identity using reflection to retrieve values and generate the mappings.
static BooleanExpression	getEqualityExpressionForObjectExpressions(ObjectExpression expr1, ObjectExpression expr2, boolean equals) Method to generate an equality/inequality expression between two ObjectExpressions.
static SQLExpression	getEscapedPatternExpression(SQLExpression patternExpr) The pattern string for representing one character.
static SQLExpression	getLiteralForOne(SQLStatement stmt) Convenience accessor for a literal for the number 1.
static NumericExpression	getNumericExpression(SQLExpression expr) Method to return a numeric expression for the supplied SQL expression.
static StringExpression	getStringExpression(SQLExpression expr) Method to convert the provided expression into a String-based expression using the datastore.
static Object	getValueForMemberOfObject(org.datanucleus.ExecutionContext ec, org.datanucleus.metadata.AbstractMemberMetaData mmd, Object object) Get the value of a managed field/property in the provided object.
static int	populatePrimaryKeyMappingsValuesForPCMapping(JavaTypeMapping[] pkMappings, Object[] pkFieldValues, int position, PersistableMapping pcMapping, org.datanucleus.metadata.AbstractClassMetaData cmd, org.datanucleus.metadata.AbstractMemberMetaData mmd, Object fieldValue, RDBMSStoreManager storeMgr, org.datanucleus.ClassLoaderResolver clr) Convenience method to populate PK mappings/values allowing for recursion where a PK field is itself a PCMapping, that itself has PK mappings, which in turn may include PCMappings.

Methods inherited from class java.lang.Object

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

Constructor Detail

ExpressionUtils

public ExpressionUtils()

Method Detail

getNumericExpression

public static NumericExpression getNumericExpression(SQLExpression expr)

Method to return a numeric expression for the supplied SQL expression. Makes use of the RDBMS function to convert to a numeric.

Parameters:

expr - The expression

Returns:

The numeric expression for this SQL expression

getLiteralForOne

public static SQLExpression getLiteralForOne(SQLStatement stmt)

Convenience accessor for a literal for the number 1.

Parameters:

stmt - The SQL statement

Returns:

The literal

getStringExpression

public static StringExpression getStringExpression(SQLExpression expr)

Method to convert the provided expression into a String-based expression using the datastore. Generates SQL like :-

 CAST({expr} AS VARCHAR(4000))
 

TODO Move this to a method so we can have datastore differences. e.g MySQL wants to cast as CHAR

Parameters:

expr - The expression

Returns:

The StringExpression

getEscapedPatternExpression

public static SQLExpression getEscapedPatternExpression(SQLExpression patternExpr)

The pattern string for representing one character. Most of databases will use the underscore character.

Parameters:

patternExpr - The expression that represents one character for a matcher/parser in the database

Returns:

the pattern string.

populatePrimaryKeyMappingsValuesForPCMapping

public static int populatePrimaryKeyMappingsValuesForPCMapping(JavaTypeMapping[] pkMappings,
                                                               Object[] pkFieldValues,
                                                               int position,
                                                               PersistableMapping pcMapping,
                                                               org.datanucleus.metadata.AbstractClassMetaData cmd,
                                                               org.datanucleus.metadata.AbstractMemberMetaData mmd,
                                                               Object fieldValue,
                                                               RDBMSStoreManager storeMgr,
                                                               org.datanucleus.ClassLoaderResolver clr)

Convenience method to populate PK mappings/values allowing for recursion where a PK field is itself a PCMapping, that itself has PK mappings, which in turn may include PCMappings. The pkMappings/pkFieldValues arrays are already created and we populate from "position".

Parameters:

pkMappings - The array of pk mappings to be populated

pkFieldValues - The array of pk field values to be populated

position - The current position needing populating

pcMapping - The PC mapping we are processing

cmd - ClassMetaData for the owning class with this PCMapping field

mmd - Field metadata for the field that this PCMapping represents

fieldValue - The value for the PCMapping field in the owning object

storeMgr - Store Manager

clr - ClassLoader resolver

Returns:

The current position (after our processing)

getValueForMemberOfObject

public static Object getValueForMemberOfObject(org.datanucleus.ExecutionContext ec,
                                               org.datanucleus.metadata.AbstractMemberMetaData mmd,
                                               Object object)

Get the value of a managed field/property in the provided object.

Parameters:

ec - execution context

mmd - metadata for the field/property

object - the pc object

Returns:

The field value

getAppIdEqualityExpression

public static BooleanExpression getAppIdEqualityExpression(Object id,
                                                           SQLExpression expr,
                                                           RDBMSStoreManager storeMgr,
                                                           org.datanucleus.ClassLoaderResolver clr,
                                                           org.datanucleus.metadata.AbstractClassMetaData acmd,
                                                           Integer index,
                                                           BooleanExpression bExpr)

Create an equality expression "(expr == id)" for an application identity using reflection to retrieve values and generate the mappings.

Parameters:

id - the identity to compare against

expr - the object expression

storeMgr - the StoreManager

clr - the ClassLoaderResolver

acmd - MetaData for the class the object id represents

index - the current index in the source expression (internal)

bExpr - the boolean equals expression (internal)

Returns:

the equality expression

getEqualityExpressionForObjectExpressions

public static BooleanExpression getEqualityExpressionForObjectExpressions(ObjectExpression expr1,
                                                                          ObjectExpression expr2,
                                                                          boolean equals)

Method to generate an equality/inequality expression between two ObjectExpressions. Either or both of the expressions can be ObjectLiterals.

Parameters:

expr1 - First expression

expr2 - Second expression

equals - Whether it is equality (otherwise inequality)

Returns:

The expression

checkAndCorrectExpressionMappingsForBooleanComparison

public static void checkAndCorrectExpressionMappingsForBooleanComparison(SQLExpression expr1,
                                                                         SQLExpression expr2)

Convenience method that compares the mappings used by the two expressions for compatibility for use in a boolean comparison (eq, noteq, gt, gteq, lt, lteq) and, if necessary, updates the mapping if one of them is a SQLLiteral and is deemed inconsistent with the other expression. Additionally, if both sides of the comparison are parameters, this will swap one to be its literal value.

Parameters:

expr1 - First expression

expr2 - Second expression

checkAndCorrectLiteralForConsistentMappingsForBooleanComparison

protected static void checkAndCorrectLiteralForConsistentMappingsForBooleanComparison(SQLLiteral lit,
                                                                                      SQLExpression expr)