org.apache.avalon.framework.parameters

Class Parameters

public class Parameters extends Object implements Serializable

The Parameters class represents a set of key-value pairs.

The Parameters object provides a mechanism to obtain values based on a String name. There are convenience methods that allow you to use defaults if the value does not exist, as well as obtain the value in any of the same formats that are in the Configuration interface.

While there are similarities between the Parameters object and the java.util.Properties object, there are some important semantic differences. First, Parameters are read-only. Second, Parameters are easily derived from Configuration objects. Lastly, the Parameters object is derived from XML fragments that look like this:


  <parameter name="param-name" value="param-value" />

Note: this class is not thread safe by default. If you require thread safety please synchronize write access to this class to prevent potential data corruption.

Version: CVS $Revision: 1.38 $ $Date: 2003/02/11 16:25:49 $

Author: Avalon Development Team

Field Summary
static Parameters	EMPTY_PARAMETERS Empty Parameters object

Method Summary
protected void	checkWriteable() Checks is this `Parameters` object is writeable.
static Parameters	fromConfiguration(Configuration configuration) Create a `Parameters` object from a `Configuration` object.
static Parameters	fromConfiguration(Configuration configuration, String elementName) Create a `Parameters` object from a `Configuration` object using the supplied element name.
static Parameters	fromProperties(Properties properties) Create a `Parameters` object from a `Properties` object.
String[]	getNames() Retrieve an array of all parameter names.
String	getParameter(String name) Retrieve the `String` value of the specified parameter.
String	getParameter(String name, String defaultValue) Retrieve the `String` value of the specified parameter.
boolean	getParameterAsBoolean(String name) Retrieve the `boolean` value of the specified parameter.
boolean	getParameterAsBoolean(String name, boolean defaultValue) Retrieve the `boolean` value of the specified parameter.
float	getParameterAsFloat(String name) Retrieve the `float` value of the specified parameter.
float	getParameterAsFloat(String name, float defaultValue) Retrieve the `float` value of the specified parameter.
int	getParameterAsInteger(String name) Retrieve the `int` value of the specified parameter.
int	getParameterAsInteger(String name, int defaultValue) Retrieve the `int` value of the specified parameter.
long	getParameterAsLong(String name) Retrieve the `long` value of the specified parameter.
long	getParameterAsLong(String name, long defaultValue) Retrieve the `long` value of the specified parameter.
Iterator	getParameterNames() Return an `Iterator` view of all parameter names.
boolean	isParameter(String name) Test if the specified parameter can be retrieved.
void	makeReadOnly() Make this Parameters read-only so that it will throw a `IllegalStateException` if someone tries to modify it.
Parameters	merge(Parameters other) Merge parameters from another `Parameters` instance into this.
void	removeParameter(String name) Remove a parameter from the parameters object
String	setParameter(String name, String value) Set the `String` value of a specified parameter.
static Properties	toProperties(Parameters params) Creates a `java.util.Properties` object from an Avalon Parameters object.

Field Detail

EMPTY_PARAMETERS

public static final Parameters EMPTY_PARAMETERS

Empty Parameters object

Since: 4.1.2

Method Detail

checkWriteable

protected final void checkWriteable()

Checks is this Parameters object is writeable.

Throws: IllegalStateException if this Parameters object is read-only

fromConfiguration

public static Parameters fromConfiguration(Configuration configuration)

Create a Parameters object from a Configuration object. This acts exactly like the following method call:

     Parameters.fromConfiguration(configuration, "parameter");

Parameters: configuration the Configuration

Returns: This Parameters instance.

Throws: ConfigurationException if an error occurs

fromConfiguration

public static Parameters fromConfiguration(Configuration configuration, String elementName)

Create a Parameters object from a Configuration object using the supplied element name.

Parameters: configuration the Configuration elementName the element name for the parameters

Returns: This Parameters instance.

Throws: ConfigurationException if an error occurs

Since: 4.1

fromProperties

public static Parameters fromProperties(Properties properties)

Create a Parameters object from a Properties object.

Parameters: properties the Properties

Returns: This Parameters instance.

getNames

public String[] getNames()

Retrieve an array of all parameter names.

Returns: the parameters names

getParameter

public String getParameter(String name)

Retrieve the String value of the specified parameter.

If the specified parameter cannot be found, an exception is thrown.

Parameters: name the name of parameter

Returns: the value of parameter

Throws: ParameterException if the specified parameter cannot be found

getParameter

public String getParameter(String name, String defaultValue)

Retrieve the String value of the specified parameter.

If the specified parameter cannot be found, defaultValue is returned.

Parameters: name the name of parameter defaultValue the default value, returned if parameter does not exist or parameter's name is null

Returns: the value of parameter

getParameterAsBoolean

public boolean getParameterAsBoolean(String name)

Retrieve the boolean value of the specified parameter.

If the specified parameter cannot be found, an exception is thrown.

Parameters: name the parameter name

Returns: the value

Throws: ParameterException if an error occurs ParameterException

getParameterAsBoolean

public boolean getParameterAsBoolean(String name, boolean defaultValue)

Retrieve the boolean value of the specified parameter.

If the specified parameter cannot be found, defaultValue is returned.

Parameters: name the parameter name defaultValue the default value if parameter does not exist or is of wrong type

Returns: the value

getParameterAsFloat

public float getParameterAsFloat(String name)

Retrieve the float value of the specified parameter.

If the specified parameter cannot be found, an exception is thrown.

Parameters: name the parameter name

Returns: the value

Throws: ParameterException if the specified parameter cannot be found or is not a Float value

getParameterAsFloat

public float getParameterAsFloat(String name, float defaultValue)

Retrieve the float value of the specified parameter.

If the specified parameter cannot be found, defaultValue is returned.

Parameters: name the parameter name defaultValue the default value if parameter does not exist or is of wrong type

Returns: the value

getParameterAsInteger

public int getParameterAsInteger(String name)

Retrieve the int value of the specified parameter.

If the specified parameter cannot be found, an exception is thrown. Hexadecimal numbers begin with 0x, Octal numbers begin with 0o and binary numbers begin with 0b, all other values are assumed to be decimal.

Parameters: name the name of parameter

Returns: the integer parameter type

Throws: ParameterException if the specified parameter cannot be found or is not an Integer value

getParameterAsInteger

public int getParameterAsInteger(String name, int defaultValue)

Retrieve the int value of the specified parameter.

If the specified parameter cannot be found, defaultValue is returned. Hexadecimal numbers begin with 0x, Octal numbers begin with 0o and binary numbers begin with 0b, all other values are assumed to be decimal.

Parameters: name the name of parameter defaultValue value returned if parameter does not exist or is of wrong type

Returns: the integer parameter type