Chapter 12: Crafting Your Own Template Language

import java.awt.*;
import java.awt.event.*;

# String name = context.evalString("//play/@name"); #
class #(name)#Play2 extends Frame {
    /* The Props for #(name)# ************/
#for "//play/prop"#
    Button #"@name"#Prop 
              = new Button("#"trait"#");
#end#

    /* The Events in the #(name)# ********/

    class PropEvent implements ActionListener {
        public void actionPerformed(ActionEvent evt) {
            Object prop = evt.getSource();
#for "//play/prop"#
  # if "position()!=1"#
	      } else
  #fi# if (prop.equals(#"@name"#Prop)) {
    #for "trait"#
                #(getPropName(context))#Prop.setLabel("#"."#")
    #end#
  #if "./script/@goto"#
                enterNewScene("#"script/@goto"#");
  #fi#
#end#
            } else {
                System.out.println("Invalid prop");
            }
        }
    }

    /* Creating and starting up the #(name)# ****/

    String currentScene;

    public #(name)#Play2() {
# String title = context.evalString("//play/title");
  if (title.equals("")) title = "No Title";
#
        super("#(title)#");
        setSize(#"//play/@width"#, #"//play/@height"#);
        setLayout(new FlowLayout());

        // initialize props
        PropEvent a = new PropEvent();
#for "//play/prop"#
        #"@name"#Prop.addActionListener(a);
#end#
        // start scene
        enterNewScene("#"//play/@start"#");
    }

    public void enterNewScene(String scene) {
        removeAll();  // remove previous scene
        currentScene = scene;
#for "//play/scene"#
  #if "position()!=1"#
	  } else
  #fi# if (scene.equals("#"@name"#")) {
  #for a "addprop"#
                add(#"@name"#Prop);
  #end#
	          setBackground(Color.decode("#"@color"#"));
#end#
        } else {
            System.out.println("Invalid scene: "+scene);
        }
        show();
    }

    public static void main(String[] args) {
        new #(name)#Play2();
    }
}

#declarations
/** gets appropriate prop name for a trait */
String getPropName(XPathContext c) throws Exception {
    String n = c.evalString("@prop");
    if (!n.equals("")) {
        return n;
    }
    return c.evalString(
          "ancestor::addprop/@name | ancestor::prop/@name");
}
#

<?xml version="1.0"?>
<tl>
package com.craigc.progen;

import org.w3c.dom.*;
import java.io.*;
import java.util.*;
<for path="//declare/@import">
import <value path="."/>;
</for>

<java>
String className = getClassName(context.evalString("//declare/@classname"));
</java>

public class <expr>className</expr> {
    Properties properties = new Properties();

<for path="//declarations">
<value path="."/>
</for>

    public boolean generate(XPathContext context, ProgramWriter out) {
        try {
<java>generate2(context, out); </java>
        } catch (Exception e) {
            System.out.println("Exception: "+e.getMessage());
            e.printStackTrace();
            return false;
        }
        return true;
    }
        
    public static void main(String[] args) {
        try {
            ProgramWriter out = args.length>=2
                ?new ProgramWriter(new FileOutputStream(args[1]))
                :new ProgramWriter(System.out);
            <expr>className</expr> pg = new <expr>className</expr>();
            for (int j=1; jlt;=args.length; ++j) {
                pg.properties.put("arg"+j, args[j-1]);
            }
            pg.generate(new XPathContext(args[0]), out);
            out.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    String[][] history = {
        { "<expr>new Date()</expr>", // date this file was generated
             <expr>quoteString(properties.getProperty("arg1"))</expr>,
             <expr>quoteString(properties.getProperty("arg2"))</expr> },
<java whitespace="reverse">
            for (int j=0; j&lt;history.length; ++j) {
                out.print("        ");
                for (int k=0; k&lt;history[j].length; ++k) {
                    out.print(quoteString(history[j][k])+", ");
                }
                out.println("}, ");
            }
</java>
    };

}

<declarations>
String ind = "    ";
int uid = 0;

public boolean generate2(XPathContext context, ProgramWriter out) {
	// See Example 12-28
}

public String quoteString(String t) {
     // add quotes and convert new lines, tabs  quotes
}

public String strip(String t) {
    // remove trailing white space characters
}

public String getClassName(String className) {
    // if className is an empty string, get class name from properties.get("arg2")
}
</declarations>

</tl>

public boolean generate2(XPathContext context, ProgramWriter out) {
    out.setIndent(out.getIndent()+ind);
    out.print(ind);
    try {
        NodeList x = context.evalNodeSet("*|text()");
        for (int j=0; j<x.getLength(); ++j) {
            Node n = (Node) x.item(j);
            boolean strip = true;
            if (j<x.getLength()-1) {
                Node n2 = (Node) x.item(j+1);
                int t2 = n2.getNodeType();
                if (t2==Node.TEXT_NODE) {
                    strip = false;
                } else if (t2==Node.ELEMENT_NODE) {
                    String ename = n2.getNodeName();
                    if (ename.equals("value") || ename.equals("expr")) {
                        strip = false;
                    }
                    context.push(n2, 1, 1);
                    String reverse = context.evalString("@whitespace");
                    if (reverse.equals("reverse")) {
                        strip = !strip;
                    }
                }
            }
            context.push(n, j+1, x.getLength());
            switch (n.getNodeType()) {
            case Node.ELEMENT_NODE:
                String ename = n.getNodeName();
                if (ename.equals("value")) {
                    out.println("out.print(context.evalString(\""
                        +context.evalString("@path")+"\"));");
                } else if (ename.equals("for")) {
                    ++uid;
                    String var = context.evalString("@var");
                    if (var.equals("")) {
                        var = "loopvar"+uid;
                    }
                    out.println("NodeList x"+uid
                        +" = context.evalNodeSet(\""
                        +context.evalString("@path")+"\");");
                    out.println("for (int j"+uid+"=0; j"+uid+"lt;x"+uid
                        +".getLength(); ++j"+uid+") {");
                    out.println(ind+"Node "+var+" = (Node) x"+uid
                        +".item(j"+uid+");");
                    out.println(ind+"context.push("+var+", j"+uid
                        +"+1, x"+uid+".getLength());");
                    generate2(context, out);
                    out.println("context.pop();");
                    out.println("}");
                } else if (ename.equals("if")) {
                    out.println("if (context.evalBoolean(" 
                      +quoteString(context.evalString("@path"))+")) {");
                    generate2(context, out);
                    out.println("\n}");
                } else if (ename.equals("else")) {
                    out.setIndent(out.getIndent()+ind);
                    out.println("} else {");
                    generate2(context, out);
                    out.setIndent(out.getIndent().substring(
                                           ind.length()));
                } else if (ename.equals("expr")) {
                    out.println("out.print("+
                        context.evalString(".")+");");
                } else if (ename.equals("java")) {
                    out.println(context.evalString("."));
                } else if (ename.equals("empty")) {
                } else if (ename.equals("declare")) {
                } else if (ename.equals("declarations")) {
                } else {
                    out.println("//Unknown Element: "+n.getNodeName());
                }
                break;
            case Node.TEXT_NODE:
                String t = context.evalString("."); // n.toString();
                if (strip) {
                    t = strip(t);
                }
                if (!t.equals("")) {
                    out.println("out.print("+quoteString(t)+");");
                }
                break;
            }
            context.pop();
        }
    } catch (Exception e) {
        System.out.println("Exception in generate2: "+e.getMessage());
        e.printStackTrace();
        return false;
    } finally {
        out.setIndent(out.getIndent().substring(ind.length()));
    }
    return true;
}