org.camunda.bpm.engine.impl.juel

Class ExpressionFactoryImpl

java.lang.Object

org.camunda.bpm.engine.impl.javax.el.ExpressionFactory

org.camunda.bpm.engine.impl.juel.ExpressionFactoryImpl

public class ExpressionFactoryImpl
extends ExpressionFactory

Expression factory implementation. This class is also used as an EL "service provider". The JUEL jar file specifies this class as el expression factory implementation in META-INF/services/javax.el.ExpressionFactory. Calling ExpressionFactory.newInstance() will then return an instance of this class, configured as described below. If no properties are specified at construction time, properties are read from

1. If the file JAVA_HOME/lib/el.properties exists and if it contains property javax.el.ExpressionFactory whose value is the name of this class, these properties are taken as default properties.
2. Otherwise, if system property javax.el.ExpressionFactory is set to the name of this class, the system properties System.getProperties() are taken as default properties.
3. el.properties on your classpath. These properties override the properties from JAVA_HOME/lib/el.properties or System.getProperties().

There are also constructors to explicitly pass in an instance of Properties. Having this, the following properties are read:

• javax.el.cacheSize - cache size (int, default is 1000)
• javax.el.methodInvocations - allow method invocations as in ${foo.bar(baz)} (boolean, default is false).
• javax.el.nullProperties - resolve null properties as in ${foo[null]} (boolean, default is false).
• javax.el.varArgs - support function/method calls using varargs (boolean, default is false).

Author:

Christoph Beck

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ExpressionFactoryImpl.Profile A profile provides a default set of language features that will define the builder's behavior.

Field Summary

Fields

Modifier and Type	Field and Description
static String	PROP_CACHE_SIZE javax.el.cacheSize
static String	PROP_METHOD_INVOCATIONS javax.el.methodInvocations
static String	PROP_NULL_PROPERTIES javax.el.nullProperties
static String	PROP_VAR_ARGS javax.el.varArgs

Constructor Summary

Constructors

Constructor and Description
ExpressionFactoryImpl() Create a new expression factory using the default builder and cache implementations.
ExpressionFactoryImpl(ExpressionFactoryImpl.Profile profile) Create a new expression factory using the default builder and cache implementations.
ExpressionFactoryImpl(ExpressionFactoryImpl.Profile profile, Properties properties) Create a new expression factory using the default builder and cache implementations.
ExpressionFactoryImpl(ExpressionFactoryImpl.Profile profile, Properties properties, TypeConverter converter) Create a new expression factory using the default builder and cache implementations.
ExpressionFactoryImpl(Properties properties) Create a new expression factory using the default builder and cache implementations.
ExpressionFactoryImpl(Properties properties, TypeConverter converter) Create a new expression factory using the default builder and cache implementations.
ExpressionFactoryImpl(TreeStore store) Create a new expression factory.
ExpressionFactoryImpl(TreeStore store, TypeConverter converter) Create a new expression factory.

Method Summary

Modifier and Type	Method and Description
Object	coerceToType(Object obj, Class<?> targetType) Coerces an object to a specific type according to the EL type conversion rules.
TreeMethodExpression	createMethodExpression(ELContext context, String expression, Class<?> expectedReturnType, Class<?>[] expectedParamTypes) Parses an expression into a MethodExpression for later evaluation.
protected TreeBuilder	createTreeBuilder(Properties properties, Builder.Feature... features) Create the factory's builder.
protected TreeStore	createTreeStore(int defaultCacheSize, ExpressionFactoryImpl.Profile profile, Properties properties) Create the factory's tree store.
protected TypeConverter	createTypeConverter(Properties properties) Create the factory's type converter.
TreeValueExpression	createValueExpression(ELContext context, String expression, Class<?> expectedType) Parses an expression into a ValueExpression for later evaluation.
ObjectValueExpression	createValueExpression(Object instance, Class<?> expectedType) Creates a ValueExpression that wraps an object instance.

Methods inherited from class org.camunda.bpm.engine.impl.javax.el.ExpressionFactory

newInstance, newInstance

Methods inherited from class java.lang.Object

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

Field Detail

PROP_METHOD_INVOCATIONS

public static final String PROP_METHOD_INVOCATIONS

javax.el.methodInvocations

See Also:

Constant Field Values

PROP_VAR_ARGS

public static final String PROP_VAR_ARGS

javax.el.varArgs

See Also:

Constant Field Values

PROP_NULL_PROPERTIES

public static final String PROP_NULL_PROPERTIES

javax.el.nullProperties

See Also:

Constant Field Values

PROP_CACHE_SIZE

public static final String PROP_CACHE_SIZE

javax.el.cacheSize

See Also:

Constant Field Values

Constructor Detail

ExpressionFactoryImpl

public ExpressionFactoryImpl()

Create a new expression factory using the default builder and cache implementations. The builder and cache are configured from el.properties (see above). The maximum cache size will be 1000 unless overridden in el.properties. The builder profile is ExpressionFactoryImpl.Profile.JEE6 (features may be overridden in el.properties).

ExpressionFactoryImpl

public ExpressionFactoryImpl(ExpressionFactoryImpl.Profile profile)

Create a new expression factory using the default builder and cache implementations. The builder and cache are configured from the specified profile and el.properties (see above). The maximum cache size will be 1000 unless overridden in el.properties.

Parameters:

profile - builder profile (features may be overridden in el.properties)

Since:

2.2

ExpressionFactoryImpl

public ExpressionFactoryImpl(Properties properties)

Create a new expression factory using the default builder and cache implementations. The builder and cache are configured using the specified properties. The maximum cache size will be 1000 unless overridden by property javax.el.cacheSize. The builder profile is ExpressionFactoryImpl.Profile.JEE6 (features may be overridden in properties).

Parameters:

properties - used to initialize this factory (may be null)

ExpressionFactoryImpl

public ExpressionFactoryImpl(ExpressionFactoryImpl.Profile profile,
                             Properties properties)

Create a new expression factory using the default builder and cache implementations. The builder and cache are configured using the specified profile and properties. The maximum cache size will be 1000 unless overridden by property javax.el.cacheSize.

Parameters:

profile - builder profile (individual features may be overridden in properties)

properties - used to initialize this factory (may be null)

Since:

2.2

ExpressionFactoryImpl

public ExpressionFactoryImpl(Properties properties,
                             TypeConverter converter)

Create a new expression factory using the default builder and cache implementations. The builder and cache are configured using the specified properties. The maximum cache size will be 1000 unless overridden by property javax.el.cacheSize. The builder profile is ExpressionFactoryImpl.Profile.JEE6 (individual features may be overridden in properties).

Parameters:

properties - used to initialize this factory (may be null)

converter - custom type converter

ExpressionFactoryImpl

public ExpressionFactoryImpl(ExpressionFactoryImpl.Profile profile,
                             Properties properties,
                             TypeConverter converter)

Create a new expression factory using the default builder and cache implementations. The builder and cache are configured using the specified profile and properties. The maximum cache size will be 1000 unless overridden by property javax.el.cacheSize.

Parameters:

profile - builder profile (individual features may be overridden in properties)

properties - used to initialize this factory (may be null)

converter - custom type converter

Since:

2.2

ExpressionFactoryImpl

public ExpressionFactoryImpl(TreeStore store)

Create a new expression factory.

Parameters:

store - the tree store used to parse and cache parse trees.

ExpressionFactoryImpl

public ExpressionFactoryImpl(TreeStore store,
                             TypeConverter converter)

Create a new expression factory.

Parameters:

store - the tree store used to parse and cache parse trees.

converter - custom type converter

Method Detail

createTreeStore

protected TreeStore createTreeStore(int defaultCacheSize,
                                    ExpressionFactoryImpl.Profile profile,
                                    Properties properties)

Create the factory's tree store. This implementation creates a new tree store using the default builder and cache implementations. The builder and cache are configured using the specified properties. The maximum cache size will be as specified unless overridden by property javax.el.cacheSize.

createTypeConverter

protected TypeConverter createTypeConverter(Properties properties)

Create the factory's type converter. This implementation takes the de.odysseus.el.misc.TypeConverter property as the name of a class implementing the de.odysseus.el.misc.TypeConverter interface. If the property is not set, the default converter (TypeConverter.DEFAULT) is used.

createTreeBuilder

protected TreeBuilder createTreeBuilder(Properties properties,
                                        Builder.Feature... features)

Create the factory's builder. This implementation takes the de.odysseus.el.tree.TreeBuilder property as a name of a class implementing the de.odysseus.el.tree.TreeBuilder interface. If the property is not set, a plain de.odysseus.el.tree.impl.Builder is used. If the configured class is a subclass of de.odysseus.el.tree.impl.Builder and which provides a constructor taking an array of Builder.Feature, this constructor will be invoked. Otherwise, the default constructor will be used.

coerceToType

public final Object coerceToType(Object obj,
                                 Class<?> targetType)

Description copied from class: ExpressionFactory

Coerces an object to a specific type according to the EL type conversion rules. An ELException is thrown if an error results from applying the conversion rules.

Specified by:

coerceToType in class ExpressionFactory

Parameters:

obj - The object to coerce.

targetType - The target type for the coercion.

Returns:

the coerced object

createValueExpression

public final ObjectValueExpression createValueExpression(Object instance,
                                                         Class<?> expectedType)

Description copied from class: ExpressionFactory

Creates a ValueExpression that wraps an object instance. This method can be used to pass any object as a ValueExpression. The wrapper ValueExpression is read only, and returns the wrapped object via its getValue() method, optionally coerced.

Specified by:

createValueExpression in class ExpressionFactory

Parameters:

instance - The object instance to be wrapped.

expectedType - The type the result of the expression will be coerced to after evaluation. There will be no coercion if it is Object.class,

Returns:

a ValueExpression that wraps the given object instance.

createValueExpression

public final TreeValueExpression createValueExpression(ELContext context,
                                                       String expression,
                                                       Class<?> expectedType)

Description copied from class: ExpressionFactory

Parses an expression into a ValueExpression for later evaluation. Use this method for expressions that refer to values. This method should perform syntactic validation of the expression. If in doing so it detects errors, it should raise an ELException.

Specified by:

createValueExpression in class ExpressionFactory

Parameters:

context - The EL context used to parse the expression. The FunctionMapper and VariableMapper stored in the ELContext are used to resolve functions and variables found in the expression. They can be null, in which case functions or variables are not supported for this expression. The object returned must invoke the same functions and access the same variable mappings regardless of whether the mappings in the provided FunctionMapper and VariableMapper instances change between calling ExpressionFactory.createValueExpression() and any method on ValueExpression. Note that within the EL, the ${} and #{} syntaxes are treated identically. This includes the use of VariableMapper and FunctionMapper at expression creation time. Each is invoked if not null, independent of whether the #{} or ${} syntax is used for the expression.

expression - The expression to parse

expectedType - The type the result of the expression will be coerced to after evaluation.

Returns:

The parsed expression

createMethodExpression

public final TreeMethodExpression createMethodExpression(ELContext context,
                                                         String expression,
                                                         Class<?> expectedReturnType,
                                                         Class<?>[] expectedParamTypes)

Description copied from class: ExpressionFactory

Parses an expression into a MethodExpression for later evaluation. Use this method for expressions that refer to methods. If the expression is a String literal, a MethodExpression is created, which when invoked, returns the String literal, coerced to expectedReturnType. An ELException is thrown if expectedReturnType is void or if the coercion of the String literal to the expectedReturnType yields an error (see Section "1.16 Type Conversion"). This method should perform syntactic validation of the expression. If in doing so it detects errors, it should raise an ELException.

Specified by:

createMethodExpression in class ExpressionFactory

Parameters:

context - The EL context used to parse the expression. The FunctionMapper and VariableMapper stored in the ELContext are used to resolve functions and variables found in the expression. They can be null, in which case functions or variables are not supported for this expression. The object returned must invoke the same functions and access the same variable mappings regardless of whether the mappings in the provided FunctionMapper and VariableMapper instances change between calling ExpressionFactory.createMethodExpression() and any method on MethodExpression. Note that within the EL, the ${} and #{} syntaxes are treated identically. This includes the use of VariableMapper and FunctionMapper at expression creation time. Each is invoked if not null, independent of whether the #{} or ${} syntax is used for the expression.

expression - The expression to parse

expectedReturnType - The expected return type for the method to be found. After evaluating the expression, the MethodExpression must check that the return type of the actual method matches this type. Passing in a value of null indicates the caller does not care what the return type is, and the check is disabled.

expectedParamTypes - The expected parameter types for the method to be found. Must be an array with no elements if there are no parameters expected. It is illegal to pass null.

Returns:

The parsed expression