net.sf.basedb.core.query
Class Expressions

java.lang.Object
  net.sf.basedb.core.query.Expressions

public class Expressions
extends Object

A factory class to create expressions.

Version:

2.0

Author:

Samuel, Nicklas

Last modified

$Date: 2011-12-02 12:09:46 +0100 (Fri, 02 Dec 2011) $

Field Summary

static Pattern

PARAMETER_REGEXP A parameter name can only contain the characters a-z, A-Z or 0-9.

Constructor Summary

Expressions()

Method Summary

static Expression	abs(Expression e) Calculate the absolute value of an expression: new expression = abs(e).
static Expression	add(Expression e1, Expression e2) Add two expressions: new expression = e1 + e2.
static Expression	aFloat(float value) Create a constant expression from a float.
static Expression	all(Query subquery) Create a subquery expression: ANY (subquery).
static Expression	any(Query subquery) Create a subquery expression: ANY (subquery).
static Expression	bool(boolean value) Create a constant expression from a boolean.
static Expression	bool(Restriction restriction) Create a boolean expression view of a restriction.
static Expression	caseWhen(Expression elseExpression, WhenStatement... whenStatements) Create a conditional CASE-WHEN expression: CASE WHEN r1 THEN e1 WHEN r2 THEN e2 ...
static Expression	divide(Expression e1, Expression e2) Divide one expression by another: new expression = e1 / e2.
static Expression	exp(Expression e) Calculate the exponential of an expression: new expression = exp(e).
private static int	getFirstNull(Object[] array) Test if there is null in the array.
static Expression	integer(int value) Create a constant expression from an integer.
static Expression	ln(Expression e) Calculate the natural logarithm of an expression: new expression = ln(e).
static Expression	log(double n, Expression e) Calculate the n-based logarithm of an expression: new expression = log(n, e).
static Expression	log10(Expression e) Calculate the 10-based logarithm of an expression: new expression = log10(e).
static Expression	log2(Expression e) Calculate the 2-based logarithm of an expression: new expression = log2(e).
static Expression	multiply(Expression e1, Expression e2) Multiply two expressions: new expression = e1 * e2.
static Expression	negate(Expression e) Negate an expression: new expression = -e1.
static Expression	parameter(String name) Create an expression for a parameter without a default value or type.
static Expression	parameter(String name, Object value) Create an expression for a parameter with a default value but no type.
static Expression	parameter(String name, Object value, Type valueType) Create an expression for a parameter with a default value and type.
static Expression	parameter(String name, Type valueType) Create an expression for a typed parameter without a default value.
static Expression	power(Expression e1, Expression e2) Calculate the first expression raised to the power of the second expression: new expression = e1 ^ e2
static Expression	selected(Select select) Create an expression for an already selected query element.
static Expression	sqrt(Expression e) Calculate the square root of an expression: new expression = sqrt(e).
static Expression	string(String value) Create a constant expression from a string.
static Expression	subtract(Expression e1, Expression e2) Subtract one expression from another: new expression = e1 - e2.
static Expression	toDate(Expression e) Get the date part from a date or timestamp expression.

Methods inherited from class java.lang.Object

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

Field Detail

PARAMETER_REGEXP

public static final Pattern PARAMETER_REGEXP

A parameter name can only contain the characters a-z, A-Z or 0-9.

Constructor Detail

Expressions

public Expressions()

Method Detail

add

public static Expression add(Expression e1,
                             Expression e2)
                      throws InvalidDataException

Add two expressions: new expression = e1 + e2.

Parameters:

e1 - The left value

e2 - The right value

Returns:

The new expression

Throws:

InvalidDataException - If any of the arguments are null

subtract

public static Expression subtract(Expression e1,
                                  Expression e2)
                           throws InvalidDataException

Subtract one expression from another: new expression = e1 - e2.

Parameters:

e1 - The left value

e2 - The right value

Returns:

The new expression

Throws:

InvalidDataException - If any of the arguments are null

divide

public static Expression divide(Expression e1,
                                Expression e2)
                         throws InvalidDataException

Divide one expression by another: new expression = e1 / e2.

Parameters:

e1 - The numerator

e2 - The denominator

Returns:

The new expression

Throws:

InvalidDataException - If any of the arguments are null

multiply

public static Expression multiply(Expression e1,
                                  Expression e2)
                           throws InvalidDataException

Multiply two expressions: new expression = e1 * e2.

Parameters:

e1 - The left value

e2 - The right value

Returns:

The new expression

Throws:

InvalidDataException - If any of the arguments are null

negate

public static Expression negate(Expression e)
                         throws InvalidDataException

Negate an expression: new expression = -e1.

Parameters:

e - The expression to negate

Returns:

The new expression

Throws:

InvalidDataException - If the argument is null

integer

public static Expression integer(int value)

Create a constant expression from an integer.

Parameters:

value - The value to create an expression for

Returns:

The expression

aFloat

public static Expression aFloat(float value)

Create a constant expression from a float.

Parameters:

value - The value to create an expression for

Returns:

The expression

string

public static Expression string(String value)
                         throws InvalidDataException

Create a constant expression from a string. Internally this is implemented as parameter with a default value. Ie. parameter(String, Object). In most cases it is better to use that method instead of this.

Parameters:

value - The string value

Returns:

The expression

Throws:

InvalidDataException - If the value is null

bool

public static Expression bool(boolean value)

Create a constant expression from a boolean.

Parameters:

value - The value to create an expression for

Returns:

The expression

Since:

3.1

bool

public static Expression bool(Restriction restriction)

Create a boolean expression view of a restriction.

Parameters:

restriction - The restriction

Returns:

The expression

Since:

3.1

parameter

public static Expression parameter(String name)
                            throws InvalidDataException

Create an expression for a parameter without a default value or type.

Parameters:

name - Name of the parameter. Can not be null.

Returns:

An expression.

Throws:

InvalidDataException - If the parameter is null.

See Also:

parameter(String, Object, Type), Query.setParameter(String, Object, Type)

parameter

public static Expression parameter(String name,
                                   Type valueType)
                            throws InvalidDataException

Create an expression for a typed parameter without a default value.

Parameters:

name - Name of the parameter. Can not be null

valueType - Type of value the parameter holds.

Returns:

An expression

Throws:

InvalidDataException - If required argument is null.

See Also:

parameter(String, Object, Type), Query.setParameter(String, Object, Type)

parameter

public static Expression parameter(String name,
                                   Object value)
                            throws InvalidDataException

Create an expression for a parameter with a default value but no type.

Parameters:

name - Name of the parameter. Can not be null.

value - Value of the parameter.

Returns:

An expression to use in queries.

Throws:

InvalidDataException - If required parameter is null.

See Also:

parameter(String, Object, Type)

parameter

public static Expression parameter(String name,
                                   Object value,
                                   Type valueType)
                            throws InvalidDataException

Create an expression for a parameter with a default value and type.

Parameters:

name - The name of the parameter. Can not be null

value - The default value of the parameter, or null if no default is needed

valueType - The type of the parameter, or null if not used

Returns:

An expression representing the parameter

Throws:

InvalidDataException - If the argument 'name' is null or contains invalid characters

See Also:

Query.setParameter(String, Object, Type), PARAMETER_REGEXP

selected

public static Expression selected(Select select)
                           throws InvalidDataException

Create an expression for an already selected query element. If an alias has been specified it will be used, otherwise the entire expression is built again.

Parameters:

select - A selected query element. Can not be null.

Returns:

A expression object representing the selected expression

Throws:

InvalidDataException - If the argument is null

log10

public static Expression log10(Expression e)
                        throws InvalidDataException

Calculate the 10-based logarithm of an expression: new expression = log10(e).

Parameters:

e - The expression to take the logarithm of

Returns:

The new expression

Throws:

InvalidDataException - If the argument is null

log2

public static Expression log2(Expression e)
                       throws InvalidDataException

Calculate the 2-based logarithm of an expression: new expression = log2(e).

Parameters:

e - The expression to take the logarithm of

Returns:

The new expression

Throws:

InvalidDataException - If the argument is null

ln

public static Expression ln(Expression e)
                     throws InvalidDataException

Calculate the natural logarithm of an expression: new expression = ln(e).

Parameters:

e - The expression to take the logarithm of

Returns:

The new expression

Throws:

InvalidDataException - If the argument is null

log

public static Expression log(double n,
                             Expression e)
                      throws InvalidDataException

Calculate the n-based logarithm of an expression: new expression = log(n, e).

Parameters:

n - The log base, must be > 0

e - The expression to take the logarithm of

Returns:

The new expression

Throws:

InvalidDataException - If the expression is null or if the base is 0 or below

exp

public static Expression exp(Expression e)
                      throws InvalidDataException

Calculate the exponential of an expression: new expression = exp(e).

Parameters:

e - The expression to take the exponential of

Returns:

The new expression

Throws:

InvalidDataException - If the argument is null

power

public static Expression power(Expression e1,
                               Expression e2)

Calculate the first expression raised to the power of the second expression: new expression = e1 ^ e2

Parameters:

e1 - The base expression

e2 - The exponent expression

Returns:

The new expression

Throws:

InvalidDataException - If some of the arguments are null

Since:

2.12

sqrt

public static Expression sqrt(Expression e)
                       throws InvalidDataException

Calculate the square root of an expression: new expression = sqrt(e).

Parameters:

e - The expression to take the square root of

Returns:

The new expression

Throws:

InvalidDataException - If the argument is null

abs

public static Expression abs(Expression e)
                      throws InvalidDataException

Calculate the absolute value of an expression: new expression = abs(e).

Parameters:

e - The expression to take the absolute value of

Returns:

The new expression

Throws:

InvalidDataException - If the argument is null

toDate

public static Expression toDate(Expression e)

Get the date part from a date or timestamp expression.

Parameters:

e - An expression which should evaluate to a date or timestamp

Returns:

The new expression

Since:

2.16

caseWhen

public static Expression caseWhen(Expression elseExpression,
                                  WhenStatement... whenStatements)
                           throws InvalidDataException

Create a conditional CASE-WHEN expression:

CASE
WHEN r1 THEN e1
WHEN r2 THEN e2
...
ELSE elseExpression
END

Parameters:

elseExpression - The optional else part of the expression

whenStatements - An array of WhenStatement:s

Returns:

The new expression

Throws:

InvalidDataException - If any of the when statements are null or if no when statements have been specified

any

public static Expression any(Query subquery)

Create a subquery expression: ANY (subquery). The expression is useful in the WHERE part of a query only. For example, to find all users that are members of a group having a name starting with A.

Query groupFilter = User.getQuery();
groupFilter.join(Hql.innerJoin("groups", "grp"));
groupFilter.restrict(Restrictions.like(Hql.property("grp", "name"), Expressions.string("A%")));
Query userQuery = User.getQuery();
userQuery.restrict(Restrictions.eq(Hql.property("id"), Expressions.any(groupFilter)));

Parameters:

subquery - The subquery

Returns:

The new expression

Throws:

InvalidDataException - If the subquery is null

Since:

2.9

all

public static Expression all(Query subquery)

Create a subquery expression: ANY (subquery).

Parameters:

subquery - The subquery

Returns:

The new expression

Throws:

InvalidDataException - If the subquery is null

Since:

2.9

See Also:

any(Query)

getFirstNull

private static int getFirstNull(Object[] array)

Test if there is null in the array.

Returns:

The index of the first null element, or -1 if no null elements are found, or 0 if the array itself is null