A view tool that allows template designers to load * an arbitrary object into the context. Any object * with a public constructor without parameters can be used * as a view tool.
*Enhancments were added to allow a tool map to be assigned to the loader * when the tool loader is constructed, allow for up to four constructor arguments, * and to optionally allow for the use of the class name loading feature. * *
THIS CLASS IS HERE AS A PROOF OF CONCEPT ONLY. IT IS NOT * INTENDED FOR USE IN PRODUCTION ENVIRONMENTS. USE AT YOUR OWN RISK.
* * @author Gabe Sidler * @author Geir Magnusson Jr. * * @version $Id: ToolLoader.java,v 1.3 2002/05/10 05:42:17 sidler Exp $ * */ public class ToolLoader { /** * controls if tools can be loaded via class name */ protected boolean classNameAllowed; /** * Maps the registered tool names to their class names */ protected Map toolMap; public static final Object[] EMPTY_OBJECT_ARRAY = new Object[ 0 ]; /** * Default constructor. * For backward compataility, this allows use of class name for tool names * with an empty tool name map. */ public ToolLoader() { this( new HashMap(), true ); } /** * Contrstructs a tool loader, initializing it with a tool map and * control of class names as tool names. * @param toolMap the tool map to use for mapping tool names to class names * @param classNameAllowed controls if a class name can be used to load * objects as tools. */ public ToolLoader( Map toolMap, boolean classNameAllowed ) { this.toolMap = toolMap; this.classNameAllowed = classNameAllowed; } /** * Loads a tool based on the tool name using the default constructor. * @param toolName the name of the tool * @return the tool. A null value is returned if no tool could be found and/or constructed * @see #load( String toolName, Object[] args ) */ public Object load( String toolName ) { return load( toolName, EMPTY_OBJECT_ARRAY ); } /** * Loads a tool based on the tool name using a constructor with arguments. * @param toolName the name of the tool * @param arg0 first constructor argument * @return the tool. A null value is returned if no tool could be found and/or constructed * @see #load( String toolName, Object[] args ) */ public Object load( String toolName, Object arg0 ) { return load( toolName, new Object[] { arg0 } ); } /** * Loads a tool based on the tool name using a constructor with arguments. * @param toolName the name of the tool * @param arg0 first constructor argument * @param arg1 second constructor argument * @return the tool. A null value is returned if no tool could be found and/or constructed * @see #load( String toolName, Object[] args ) */ public Object load( String toolName, Object arg0, Object arg1 ) { return load( toolName, new Object[] { arg0, arg1 } ); } /** * Loads a tool based on the tool name using a constructor with arguments. * @param toolName the name of the tool * @param arg0 first constructor argument * @param arg1 second constructor argument * @param arg2 third constructor argument * @return the tool. A null value is returned if no tool could be found and/or constructed * @see #load( String toolName, Object[] args ) */ public Object load( String toolName, Object arg0, Object arg1, Object arg2 ) { return load( toolName, new Object[] { arg0, arg1, arg2 } ); } /** * Loads a tool based on the tool name using a constructor with arguments. * @param toolName the name of the tool * @param arg0 first constructor argument * @param arg1 second constructor argument * @param arg2 third constructor argument * @param arg3 fourth constructor argument * @return the tool. A null value is returned if no tool could be found and/or constructed * @see #load( String toolName, Object[] args ) */ public Object load( String toolName, Object arg0, Object arg1, Object arg2, Object arg3 ) { return load( toolName, new Object[] { arg0, arg1, arg2, arg3 } ); } /** * Loads a tool based on the tool name. The tool name is looked up in the * tool map. If found, the value of the map is used as the class name of * the tool. *If the tool name is not found in the tool map and the tool loader is * configured to use the tool name as a class name, the toolName will be used * as the class name.
* @param toolName the name of the tool * @param args arguments to the contructor of the class for the tool. If null, * the default constructor will be used. * @return the tool. A null value is returned if no tool could be found and/or constructed */ public Object load( String toolName, Object[] args ) { Object tool = null; // lookup the toolname here in the toolmap Object mapValue = toolMap.get( toolName ); if ( mapValue != null && mapValue instanceof String ) { tool = createTool( (String) mapValue, args ); } else if ( tool == null && classNameAllowed ) { // treat toolName as a class name tool = createTool( toolName, args ); } return tool; } /** * Creates the tool from the className and arguments. * @param the class name of the tool to construct. * @param args arguments to the contructor of the class for the tool. If null, * the default constructor will be used. * @return the tool. A null value is returned if no tool could be found and/or constructed */ protected Object createTool( String className, Object[] args ) { Object tool = null; try { Class toolClass = Class.forName( className ); if ( args == null || args.length == 0 ) { tool = toolClass.newInstance(); } else { Constructor constructor = toolClass.getConstructor( createParameterTypes( args ) ); tool = constructor.newInstance( args ); } } catch ( Exception e ) { // do nothing (log error?) } return tool; } /** * Creates an array of classes for each parameter of the constructor based on * the class of each argument. * @param args the array of arguments * @return an array of parameters types */ protected static Class[] createParameterTypes( Object[] args ) { Class parameterTypes[] = new Class[ args.length ]; for ( int i = 0; i < args.length; i++ ) { parameterTypes[i] = args[i].getClass(); } return parameterTypes; } /** * Indicates if class names are allowed for tool lookup. * @return true, if class names are allowed; false, if not. */ public boolean isClassNameAllowed() { return this.classNameAllowed; } }