sunlabs.brazil.properties

Class ExprProps

public class ExprProps extends Properties

ExprProps is a subclass of Properties that is "smart" in the sense that it wraps a Calculator object, passing get and getProperty keys to the Calculator for processing.

Keys are first searched for in the Properties object. If not found, the key is passed to the getValue method of the wrapped Calculator object. The Calculator will return null if the key consists of only a name or Brazil token and that name/token evaluates to 0. In this case, a value associated with the key can not be "found" and the get or getpropertymethod returns null also.

Only property names that "look" like expressions (e.g. contain at least one of characters in [&|*+/%=!<>-]) are passed to the calculator.

Version: 2.3, 04/05/24

Author: Steve Drach <drach@sun.com>

See Also: java.util.Properties Calculator ExprPropsHandler

Constructor Summary
	ExprProps() This constructor creates a `Calculator` instance with this instance of `ExprProps` as it's symbol table.
	ExprProps(Properties defaults) This constructor creates a `Calculator` instance with this instance of `ExprProps` as it's symbol table and with the `Properties` instance referenced by the parameter `defaults` as it's set of default values.
	ExprProps(Request request) This constructor creates a `Calculator` instance with `request.props` as it's symbol table.
	ExprProps(Request request, Properties defaults) This constructor creates a `Calculator` instance with `request.props` as it's symbol table and with the `Properties` instance referenced by the parameter `defaults` as it's set of default values.

Method Summary
Object	get(Object key) Returns the value to which the specified key is mapped in this `Hashtable`.
String	getProperty(String key) Searches for the property with the specified key in this property list.

Constructor Detail

ExprProps

public ExprProps()

This constructor creates a Calculator instance with this instance of ExprProps as it's symbol table.

ExprProps

public ExprProps(Properties defaults)

This constructor creates a Calculator instance with this instance of ExprProps as it's symbol table and with the Properties instance referenced by the parameter defaults as it's set of default values.

Parameters: defaults the defaults

ExprProps

public ExprProps(Request request)

This constructor creates a Calculator instance with request.props as it's symbol table.

Parameters: request the Request instance

ExprProps

public ExprProps(Request request, Properties defaults)

This constructor creates a Calculator instance with request.props as it's symbol table and with the Properties instance referenced by the parameter defaults as it's set of default values.

Parameters: request the Request instance defaults the defaults

Method Detail

get

public Object get(Object key)

Returns the value to which the specified key is mapped in this Hashtable. If the key is not found, then it's value is computed by treating the key as an arithmetic expression or statement.

If, during the computation, an ArithmeticException is thrown, the key compute.error is set in the base Properties. The value associated with the key is an error message.

Parameters: key the Hashtable key

Returns: the value in this table with the specified key or null

getProperty

public String getProperty(String key)

Searches for the property with the specified key in this property list. If the key is not found in this property list, then it's value is computed by treating the key as an arithmetic expression or statement.

If, during the computation, an ArithmeticException is thrown, the key compute.error is set in the base Properties. The value associated with the key is an error message.

If the result of the computation is null, the default property list, and its defaults, recursively, are then checked. The method returns null if the property is not found.

Parameters: key the property key

Returns: the value in this property list with the specified key or null