org.zkoss.xel

Class Expressions

java.lang.Object

org.zkoss.xel.Expressions

public class Expressions
extends Object

Utilities to use XEL.

Since:

3.0.0

Author:

tomyeh

Field Summary

Fields

Modifier and Type	Field and Description
static Expression	DUMMY_EXPRESSION An dummy expression that does nothing.
static FunctionMapper	EMPTY_MAPPER An empty function mapper, i.e., it has no function defined at all.
static VariableResolver	EMPTY_RESOLVER An empty variable resolver, i.e., it has no variable defined at all.

Constructor Summary

Constructors

Constructor and Description
Expressions()

Method Summary

Modifier and Type	Method and Description
static Object	evaluate(XelContext ctx, String expression, Class<?> expectedType) Evaluates an expression.
static Class<? extends ExpressionFactory>	getExpressionFactoryClass() Returns the implementation of the expression factory that is used by the whole system, or null to use the system default.
static ExpressionFactory	newExpressionFactory() Instantiates an instance of ExpressionFactory.
static ExpressionFactory	newExpressionFactory(Class<? extends ExpressionFactory> expfcls) Instantiates an instance of ExpressionFactory.
static void	setExpressionFactoryClass(Class<? extends ExpressionFactory> expfcls) Sets the implementation of the expression factory that shall be used by the whole system, or null to use the system default.

Methods inherited from class java.lang.Object

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

Field Detail

EMPTY_MAPPER

public static final FunctionMapper EMPTY_MAPPER

An empty function mapper, i.e., it has no function defined at all. It is serializable.

EMPTY_RESOLVER

public static final VariableResolver EMPTY_RESOLVER

An empty variable resolver, i.e., it has no variable defined at all. It is serializable.

DUMMY_EXPRESSION

public static final Expression DUMMY_EXPRESSION

An dummy expression that does nothing. It is usually used as a flag to denote exceptional cases. It it serializable.

Constructor Detail

Expressions

public Expressions()

Method Detail

newExpressionFactory

public static final ExpressionFactory newExpressionFactory()
                                                    throws XelException

Instantiates an instance of ExpressionFactory.

The default class is ELFactory, which supports EL 2.0. If you run under JVM 1.5 or later and deploy zel.jar in your class path, the default class is then ELFactory which supports EL 2.2. To override it, you can specify the class by calling setExpressionFactoryClass(java.lang.Class<? extends org.zkoss.xel.ExpressionFactory>), or use newExpressionFactory(Class) instead.

For the ZK user, you can override it with zk.xml or org.zkoss.zk.ui.util.Configuration.

Throws:

XelException - if the specified class failed to load, or instantiate.

newExpressionFactory

public static final ExpressionFactory newExpressionFactory(Class<? extends ExpressionFactory> expfcls)

Instantiates an instance of ExpressionFactory.

The default class is ELFactory, which supports EL 2.0. If you run under JVM 1.5 or later and deploy zel.jar in your class path, the default class is then ELFactory which supports EL 2.2. To override it, you can specify the class by calling setExpressionFactoryClass(java.lang.Class<? extends org.zkoss.xel.ExpressionFactory>), or specifying the class you prefer in the expfcls argument.

For the ZK user, you can override it with zk.xml or org.zkoss.zk.ui.util.Configuration.

Parameters:

expfcls - the class that implements ExpressionFactory, or null to use the default.

Throws:

XelException - if the specified class failed to load, or instantiate.

evaluate

public static final Object evaluate(XelContext ctx,
                                    String expression,
                                    Class<?> expectedType)
                             throws XelException

Evaluates an expression.

Parameters:

ctx - the context information to evaluate the expression It can be null, in which case no functions are supported for this invocation.

expression - the expression to be evaluated. Note: the expression is enclosed with ${ and }, regardless of what implementation is used.

expectedType - the expected type of the result of the evaluation

Throws:

XelException

setExpressionFactoryClass

public static final void setExpressionFactoryClass(Class<? extends ExpressionFactory> expfcls)

Sets the implementation of the expression factory that shall be used by the whole system, or null to use the system default.

Default: null - it means ELFactory, which supports EL 2.0. If you run under JVM 1.5 or later and deploy zel.jar in your class path, the default class is then ELFactory which supports EL 2.2.

Note: you can only specify an implementation that is compatible with JSP EL here, since all built-in pages depend on it.

Parameters:

expfcls - the implementation class, or null to use the default. Note: expfcls must implement ExpressionFactory. If null, the system default is used.

getExpressionFactoryClass

public static final Class<? extends ExpressionFactory> getExpressionFactoryClass()

Returns the implementation of the expression factory that is used by the whole system, or null to use the system default.

See Also:

setExpressionFactoryClass(java.lang.Class<? extends org.zkoss.xel.ExpressionFactory>)