* js> defineClass("File")
* js> file = new File("myfile.txt");
* [object File]
* js> file.writeLine("one"); only now is file actually opened
* js> file.writeLine("two");
* js> file.writeLine("thr", "ee");
* js> file.close(); must close file before we can reopen for reading
* js> var a = file.readLines(); creates and fills an array with the contents of the file
* js> a;
* one,two,three
* js>
*
*
*
* File errors or end-of-file signaled by thrown Java exceptions will
* be wrapped as JavaScript exceptions when called from JavaScript,
* and may be caught within JavaScript.
*
* @author Norris Boyd
*/
public class File extends ScriptableObject {
/**
* The zero-parameter constructor.
*
* When Context.defineClass is called with this class, it will
* construct File.prototype using this constructor.
*/
public File() {
}
/**
* The Java method defining the JavaScript File constructor.
*
* If the constructor has one or more arguments, and the
* first argument is not undefined, the argument is converted
* to a string as used as the filename.* * Otherwise System.in or System.out is assumed as appropriate * to the use. */ public static Scriptable jsConstructor(Context cx, Object[] args, Function ctorObj, boolean inNewExpr) { File result = new File(); if (args.length == 0 || args[0] == Context.getUndefinedValue()) { result.name = ""; result.file = null; } else { result.name = Context.toString(args[0]); result.file = new java.io.File(result.name); } return result; } /** * Returns the name of this JavaScript class, "File". */ public String getClassName() { return "File"; } /** * Get the name of the file. * * Used to define the "name" property. */ public String jsGet_name() { return name; } /** * Read the remaining lines in the file and return them in an array. * * Implements a JavaScript function.
* * This is a good example of creating a new array and setting * elements in that array. * * @exception IOException if an error occurred while accessing the file * associated with this object */ public Object jsFunction_readLines() throws IOException { Vector v = new Vector(); String s; while ((s = jsFunction_readLine()) != null) { v.addElement(s); } Object[] lines = new Object[v.size()]; v.copyInto(lines); Scriptable scope = ScriptableObject.getTopLevelScope(this); Context cx = Context.getCurrentContext(); return cx.newObject(scope, "Array", lines); } /** * Read a line. * * Implements a JavaScript function. * @exception IOException if an error occurred while accessing the file * associated with this object, or EOFException if the object * reached the end of the file */ public String jsFunction_readLine() throws IOException { return getReader().readLine(); } /** * Read a character. * * @exception IOException if an error occurred while accessing the file * associated with this object, or EOFException if the object * reached the end of the file */ public String jsFunction_readChar() throws IOException { int i = getReader().read(); if (i == -1) return null; char[] charArray = { (char) i }; return new String(charArray); } /** * Write strings. * * Implements a JavaScript function.
* * This function takes a variable number of arguments, converts * each argument to a string, and writes that string to the file. * @exception IOException if an error occurred while accessing the file * associated with this object */ public static void jsFunction_write(Context cx, Scriptable thisObj, Object[] args, Function funObj) throws IOException { write0(thisObj, args, false); } /** * Write strings and a newline. * * Implements a JavaScript function. * @exception IOException if an error occurred while accessing the file * associated with this object * */ public static void jsFunction_writeLine(Context cx, Scriptable thisObj, Object[] args, Function funObj) throws IOException { write0(thisObj, args, true); } public int jsGet_lineNumber() throws FileNotFoundException { return getReader().getLineNumber(); } /** * Close the file. It may be reopened. * * Implements a JavaScript function. * @exception IOException if an error occurred while accessing the file * associated with this object */ public void jsFunction_close() throws IOException { if (reader != null) { reader.close(); reader = null; } else if (writer != null) { writer.close(); writer = null; } } /** * Finalizer. * * Close the file when this object is collected. */ protected void finalize() { try { jsFunction_close(); } catch (IOException e) { } } /** * Get the Java reader. */ public Object jsFunction_getReader() { if (reader == null) return null; // Here we use toObject() to "wrap" the BufferedReader object // in a Scriptable object so that it can be manipulated by // JavaScript. Scriptable parent = ScriptableObject.getTopLevelScope(this); return Context.javaToJS(reader, parent); } /** * Get the Java writer. * * @see File#jsFunction_getReader * */ public Object jsFunction_getWriter() { if (writer == null) return null; Scriptable parent = ScriptableObject.getTopLevelScope(this); return Context.javaToJS(writer, parent); } /** * Get the reader, checking that we're not already writing this file. */ private LineNumberReader getReader() throws FileNotFoundException { if (writer != null) { throw Context.reportRuntimeError("already writing file \"" + name + "\""); } if (reader == null) reader = new LineNumberReader(file == null ? new InputStreamReader(System.in) : new FileReader(file)); return reader; } /** * Perform the guts of write and writeLine. * * Since the two functions differ only in whether they write a * newline character, move the code into a common subroutine. * */ private static void write0(Scriptable thisObj, Object[] args, boolean eol) throws IOException { File thisFile = checkInstance(thisObj); if (thisFile.reader != null) { throw Context.reportRuntimeError("already writing file \"" + thisFile.name + "\""); } if (thisFile.writer == null) thisFile.writer = new BufferedWriter( thisFile.file == null ? new OutputStreamWriter(System.out) : new FileWriter(thisFile.file)); for (int i=0; i < args.length; i++) { String s = Context.toString(args[i]); thisFile.writer.write(s, 0, s.length()); } if (eol) thisFile.writer.newLine(); } /** * Perform the instanceof check and return the downcasted File object. * * This is necessary since methods may reside in the File.prototype * object and scripts can dynamically alter prototype chains. For example: *
* js> defineClass("File");
* js> o = {};
* [object Object]
* js> o.__proto__ = File.prototype;
* [object File]
* js> o.write("hi");
* js: called on incompatible object
*
* The runtime will take care of such checks when non-static Java methods
* are defined as JavaScript functions.
*/
private static File checkInstance(Scriptable obj) {
if (obj == null || !(obj instanceof File)) {
throw Context.reportRuntimeError("called on incompatible object");
}
return (File) obj;
}
/**
* Some private data for this class.
*/
private String name;
private java.io.File file; // may be null, meaning to use System.out or .in
private LineNumberReader reader;
private BufferedWriter writer;
}