org.apache.avalon.framework.parameters

Class Parameters

java.lang.Object

org.apache.avalon.framework.parameters.Parameters

All Implemented Interfaces:

Serializable

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:

$Id: Parameters.java 30977 2004-07-30 03:57:54 -0500 (Fri, 30 Jul 2004) niclas $

Author:

Avalon Development Team

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static Parameters	EMPTY_PARAMETERS Empty Parameters object

Constructor Summary

Constructors

Constructor and Description
Parameters()

Method Summary

Modifier and Type	Method and Description
protected void	checkWriteable() Checks is this Parameters object is writeable.
boolean	equals(Object other) Compare this parameters instance with the supplied object for equality.
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() Deprecated. Use getNames() instead
int	hashCode() Returns a hashed value of the Parameters instance.
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.
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

EMPTY_PARAMETERS

public static final Parameters EMPTY_PARAMETERS

Empty Parameters object

Since:

4.1.2

Constructor Detail

Parameters

public Parameters()

Method Detail

setParameter

public String setParameter(String name,
                           String value)
                    throws IllegalStateException

Set the String value of a specified parameter.

If the specified value is null the parameter is removed.

Parameters:

name - a String value

value - a String value

Returns:

The previous value of the parameter or null.

Throws:

IllegalStateException - if the Parameters object is read-only

removeParameter

public void removeParameter(String name)

Remove a parameter from the parameters object

Parameters:

name - a String value

Since:

4.1

getParameterNames

public Iterator getParameterNames()

Deprecated. Use getNames() instead

Return an Iterator view of all parameter names.

Returns:

a iterator of parameter names

getNames

public String[] getNames()

Retrieve an array of all parameter names.

Returns:

the parameters names

isParameter

public boolean isParameter(String name)

Test if the specified parameter can be retrieved.

Parameters:

name - the parameter name

Returns:

true if parameter is a name

getParameter

public String getParameter(String name)
                    throws ParameterException

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

getParameterAsInteger

public int getParameterAsInteger(String name)
                          throws ParameterException

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

getParameterAsLong

public long getParameterAsLong(String name)
                        throws ParameterException

Retrieve the long 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 long parameter type

Throws:

ParameterException - if the specified parameter cannot be found or is not a Long value.

getParameterAsLong

public long getParameterAsLong(String name,
                               long defaultValue)

Retrieve the long 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 long parameter type

getParameterAsFloat

public float getParameterAsFloat(String name)
                          throws ParameterException

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

getParameterAsBoolean

public boolean getParameterAsBoolean(String name)
                              throws ParameterException

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

merge

public Parameters merge(Parameters other)

Merge parameters from another Parameters instance into this.

Parameters:

other - the other Parameters

Returns:

This Parameters instance.

makeReadOnly

public void makeReadOnly()

Make this Parameters read-only so that it will throw a IllegalStateException if someone tries to modify it.

equals

public boolean equals(Object other)

Compare this parameters instance with the supplied object for equality. The equality is mainly driven by the underlying HashMap which forms the basis of the class. I.e. if the underlying HashMaps are equal and the Readonly attributes are equal in the Parameters instances being compared, then this method returns equality.

Overrides:

equals in class Object

Parameters:

other - the object to compare this parameters instance with

Returns:

true if this parameters instance is equal to the supplied object

Since:

4.3

hashCode

public int hashCode()

Returns a hashed value of the Parameters instance. This method returns a semi-unique value for all instances, yet an identical value for instances where equals() returns true.

Overrides:

hashCode in class Object

Returns:

a hashed value of the instance

Since:

4.3

toString

public String toString()

Overrides:

toString in class Object

checkWriteable

protected final void checkWriteable()
                             throws IllegalStateException

Checks is this Parameters object is writeable.

Throws:

IllegalStateException - if this Parameters object is read-only

fromConfiguration

public static Parameters fromConfiguration(Configuration configuration)
                                    throws ConfigurationException

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)
                                    throws ConfigurationException

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.

toProperties

public static Properties toProperties(Parameters params)

Creates a java.util.Properties object from an Avalon Parameters object.

Parameters:

params - a Parameters instance

Returns:

a Properties instance