org.apache.avalon.framework.parameters
Class Parameters

java.lang.Object
  extended byorg.apache.avalon.framework.parameters.Parameters
All Implemented Interfaces:
java.io.Serializable

public class Parameters
extends java.lang.Object
implements java.io.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 08:57:54Z niclas $
Author:
Avalon Development Team
See Also:
Serialized Form

Field Summary
static Parameters EMPTY_PARAMETERS
          Empty Parameters object
 
Constructor Summary
Parameters()
           
 
Method Summary
protected  void checkWriteable()
          Checks is this Parameters object is writeable.
 boolean equals(java.lang.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, java.lang.String elementName)
          Create a Parameters object from a Configuration object using the supplied element name.
static Parameters fromProperties(java.util.Properties properties)
          Create a Parameters object from a Properties object.
 java.lang.String[] getNames()
          Retrieve an array of all parameter names.
 java.lang.String getParameter(java.lang.String name)
          Retrieve the String value of the specified parameter.
 java.lang.String getParameter(java.lang.String name, java.lang.String defaultValue)
          Retrieve the String value of the specified parameter.
 boolean getParameterAsBoolean(java.lang.String name)
          Retrieve the boolean value of the specified parameter.
 boolean getParameterAsBoolean(java.lang.String name, boolean defaultValue)
          Retrieve the boolean value of the specified parameter.
 float getParameterAsFloat(java.lang.String name)
          Retrieve the float value of the specified parameter.
 float getParameterAsFloat(java.lang.String name, float defaultValue)
          Retrieve the float value of the specified parameter.
 int getParameterAsInteger(java.lang.String name)
          Retrieve the int value of the specified parameter.
 int getParameterAsInteger(java.lang.String name, int defaultValue)
          Retrieve the int value of the specified parameter.
 long getParameterAsLong(java.lang.String name)
          Retrieve the long value of the specified parameter.
 long getParameterAsLong(java.lang.String name, long defaultValue)
          Retrieve the long value of the specified parameter.
 java.util.Iterator getParameterNames()
          Deprecated. Use getNames() instead
 int hashCode()
          Returns a hashed value of the Parameters instance.
 boolean isParameter(java.lang.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(java.lang.String name)
          Remove a parameter from the parameters object
 java.lang.String setParameter(java.lang.String name, java.lang.String value)
          Set the String value of a specified parameter.
static java.util.Properties toProperties(Parameters params)
          Creates a java.util.Properties object from an Avalon Parameters object.
 java.lang.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 java.lang.String setParameter(java.lang.String name,
                                     java.lang.String value)
                              throws java.lang.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:
java.lang.IllegalStateException - if the Parameters object is read-only

removeParameter

public void removeParameter(java.lang.String name)
Remove a parameter from the parameters object

Parameters:
name - a String value
Since:
4.1

getParameterNames

public java.util.Iterator getParameterNames()
Deprecated. Use getNames() instead

Return an Iterator view of all parameter names.

Returns:
a iterator of parameter names

getNames

public java.lang.String[] getNames()
Retrieve an array of all parameter names.

Returns:
the parameters names

isParameter

public boolean isParameter(java.lang.String name)
Test if the specified parameter can be retrieved.

Parameters:
name - the parameter name
Returns:
true if parameter is a name

getParameter

public java.lang.String getParameter(java.lang.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 java.lang.String getParameter(java.lang.String name,
                                     java.lang.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(java.lang.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(java.lang.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(java.lang.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(java.lang.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(java.lang.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(java.lang.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(java.lang.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(java.lang.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(java.lang.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.

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.

Returns:
a hashed value of the instance
Since:
4.3

toString

public java.lang.String toString()

checkWriteable

protected final void checkWriteable()
                             throws java.lang.IllegalStateException
Checks is this Parameters object is writeable.

Throws:
java.lang.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,
                                           java.lang.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(java.util.Properties properties)
Create a Parameters object from a Properties object.

Parameters:
properties - the Properties
Returns:
This Parameters instance.

toProperties

public static java.util.Properties toProperties(Parameters params)
Creates a java.util.Properties object from an Avalon Parameters object.

Parameters:
params - a Parameters instance
Returns:
a Properties instance


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