functioninvocation.java

jBpm是一个灵活可扩展的工作流管理系统。作为jBpm运行时server输入的业务流程使用简单强大的语言表达并打包在流程档案中

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package org.jbpm.jpdl.el.impl;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Iterator;
import java.util.List;

import org.jbpm.jpdl.el.ELException;
import org.jbpm.jpdl.el.FunctionMapper;
import org.jbpm.jpdl.el.VariableResolver;

/**
 *
 * <p>Represents a function call.</p>
 * 
 * @author Shawn Bayern (in the style of Nathan's other classes)
 **/

public class FunctionInvocation
  extends Expression
{
  //-------------------------------------
  // Properties
  //-------------------------------------
  // property index

  private String functionName;
  private List argumentList;
  public String getFunctionName() { return functionName; }
  public void setFunctionName(String f) { functionName = f; }
  public List getArgumentList() { return argumentList; }
  public void setArgumentList(List l) { argumentList = l; }

  //-------------------------------------
  /**
   * Constructor
   **/
  public FunctionInvocation (String functionName, List argumentList)
  {
    this.functionName = functionName;
    this.argumentList = argumentList;
  }

  //-------------------------------------
  // Expression methods
  //-------------------------------------
  /**
   * Returns the expression in the expression language syntax
   **/
  public String getExpressionString ()
  {
    StringBuffer b = new StringBuffer();
    b.append(functionName);
    b.append("(");
    Iterator i = argumentList.iterator();
    while (i.hasNext()) {
      b.append(((Expression) i.next()).getExpressionString());
      if (i.hasNext())
        b.append(", ");
    }
    b.append(")");
    return b.toString();
  }


  //-------------------------------------
  /**
   *
   * Evaluates by looking up the name in the VariableResolver
   **/
  public Object evaluate (VariableResolver pResolver,
			  FunctionMapper functions,
                          Logger pLogger)
    throws ELException
  {

    // if the Map is null, then the function is invalid
    if (functions == null)
      pLogger.logError(Constants.UNKNOWN_FUNCTION, functionName);

    // normalize function name
    String prefix = null;
    String localName = null;
    int index = functionName.indexOf( ':' );
    if (index == -1) {
      prefix = "";
      localName = functionName;
    } else {
      prefix = functionName.substring( 0, index );
      localName = functionName.substring( index + 1 );
    }

    // ensure that the function's name is mapped
    Method target = (Method) functions.resolveFunction(prefix, localName);
    if (target == null)
      pLogger.logError(Constants.UNKNOWN_FUNCTION, functionName);

    // ensure that the number of arguments matches the number of parameters
    Class[] params = target.getParameterTypes();
    if (params.length != argumentList.size())
      pLogger.logError(Constants.INAPPROPRIATE_FUNCTION_ARG_COUNT,
		       functionName, new Integer(params.length),
		       new Integer(argumentList.size()));

    // now, walk through each parameter, evaluating and casting its argument
    Object[] arguments = new Object[argumentList.size()];
    for (int i = 0; i < params.length; i++) {
      // evaluate
      arguments[i] = ((Expression) argumentList.get(i)).evaluate(pResolver,
								 functions,
								 pLogger);
      // coerce
      arguments[i] = Coercions.coerce(arguments[i], params[i], pLogger);
    }

    // finally, invoke the target method, which we know to be static
    try {
      return (target.invoke(null, arguments));
    } catch (InvocationTargetException ex) {
      pLogger.logError(Constants.FUNCTION_INVOCATION_ERROR,
			ex.getTargetException(),
			functionName);
      return null;
    } catch (Exception ex) {
      pLogger.logError(Constants.FUNCTION_INVOCATION_ERROR, ex, functionName);
      return null;
    }
  }

  //-------------------------------------
}