core/loggers/FileLogger.java

//---PACKAGE DECLARATION---
package uk.ac.ukc.iscream.core.loggers;

//---IMPORTS---
import uk.ac.ukc.iscream.util.*;
import uk.ac.ukc.iscream.core.*;
import java.util.Date;
import java.text.DateFormat;
import java.util.Locale;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;

/**
 * The FileLogger is an implementation of the LoggerImpl defined
 * in the associated interface. It provides quite extensive features to allow
 * logging ot a text file.
 *
 * @author  $Author: ajm4 $
 * @version $Id: FileLogger.java,v 1.3 2000/12/12 18:28:19 ajm4 Exp $
 */
public class FileLogger implements LoggerImpl {

//---FINAL ATTRIBUTES---

    /**
     * The current CVS revision of this class
     */
    public final String REVISION = "$Revision: 1.3 $";
    
//---STATIC METHODS---

//---CONSTRUCTORS---

        /**
         * Creates a new FileLogger.
         *
         * The constructor checks that writing will be ok, then sets up the
         * writer. It makes use of the fileCheck() method found later on to
         * ensure writing will be ok, and throws an IOException if there is
         * a problem. Errors at this stage cannot be logged because the
         * logging mechanism has not be setup completely, so any problems
         * are printed to the screen in the same format used for logging.
         * 
         * @throws IOException if there is a problem with the file check.
         */
    public FileLogger() throws IOException{
        _verbosityLevel = Integer.parseInt(System.getProperty("uk.ac.ukc.iscream.Verbosity"));
        filename = System.getProperty("uk.ac.ukc.iscream.LoggerClass.FileLogger.filename");
                // Perform file check to make sure writing is ok
        if(!fileCheck()){
                        // Have to system.out.println errors because logging mechanism failed !
            System.out.println(formatLogLine(this.toString(), "File check failed, construction terminated"));
            throw new IOException("File check failed, unable to create FileLog");
        }
        try{
                        // Setup the writer
            writer = new BufferedWriter(new FileWriter(filename, true));
                        // File is now open
                        open = true;
        }
        catch(IOException e){
            System.out.println(formatLogLine(toString(), "Attempt to setup writer failed - " + e.getMessage()));
        }
                // Put an initial line into the log
        write(toString(), Logger.SYSINIT, "started");
        write(toString(), Logger.SYSMSG, "using verbosity " + _verbosityLevel);
    }

//---PUBLIC METHODS---
    
        /**
         * The write() method writes a line of log to the file, prepending
         * it with some information about where to line came from and the
         * date. This formatting is handled by the formatLogLine() method.
         * There is some synchronisation here due to problems with the logfiles
         * having multiple lines written on the same line, followed by dotted
         * newlines in the wrong places. This is due to this method being
         * called by multiple threads.
         * 
         * @param source A string representation of the calling object.
         * @param message The message to be logged.
         */
    public synchronized void write(String source, int verbosity, String message) {
                // Check to make sure file is open
                if(open){
                        // Produce a nicely formatted line for the logfile
                        String line = formatLogLine(source, message);
                        try{
                                // We have to synchronize here due to problems with two write()'s being called before a newLine()
                                synchronized(writer){
                                        // Attempt to write the line
                                        writer.write(line);
                                        // Best to use newLine() as it will use the correct platform encoding
                                        writer.newLine();
                                }
                                // Make sure the line is written immeidiately
                                writer.flush();
                        }
                        catch(IOException e){
                                // We'd best log the error
                        System.out.println(formatLogLine(this.toString(), "Writing to logfile failed - " + e.getMessage()));
                                // As it's an IOException we should suspend logging
                                open = false;
                }
                }
                else{
                        // If file is not open we should print this to the screen
                        System.out.println(formatLogLine(this.toString(), "Write failed - file not open"));
                }
    }
 
        /**
         * The clear() method erases the contents of the logfile. It does
         * this in a very clumsy way - by closing the writer and opening a
         * new one which is set not to append. This results in the logfile
         * being overwritten, which effectively erases it.
         */
    public void clear(){
                // Check file is open
                if(open){
                        write(toString(), Logger.SYSMSG, "Attempting to clear logfile");
                        try{
                                // Close appending writer
                                open = false;
                                writer.close();
                                // Open a non-appending writer
                                writer = new BufferedWriter(new FileWriter(filename));
                                open = true;
                        }
                        catch(IOException e){
                                // We'd best log the error
                                write(toString(), Logger.ERROR, "Attempt to clear logfile failed - "+e.getMessage());
                                // As it's an IOException we should suspend logging
                                open = false;
                        }
                }
                else{
                        // If file is not open we should print this to the screen
                        System.out.println(formatLogLine(toString(), "Clearing failed - file not open"));
                }
    }
    
        /**
         * The close() method closes the logfile and no more data can be written.
         * If writing is attempted after close() has been called an error will be
         * generated. The open() method can be used to reopen or open a new file.
         */
    public void close(){
                // Check to see if a file is open
                if(open){
                        write(toString(), Logger.SYSMSG, "Attempting to terminate logging");
                        try{
                                open = false;
                        writer.close();         
                        }
                        catch(IOException e){
                                write(toString(), Logger.ERROR, "Attempt to close logfile failed - " + e.getMessage());
                                // As it's an IOException we should suspend logging
                                open = false;
                        }
                }
                else{
                        // If file is not open we should print this to the screen
                        System.out.println(formatLogLine(toString(), "Close failed - file not open"));
                }
    }
    
        /**
         * The open() method opens a new file after the close() method has
         * been called on the FileLog. This enables the user to easily change
         * the file to which the log is being written. An error is generated
         * if a file is already open.
         * 
         * @param filename The new file to write to.
         * @throws IOException if the file cannot be written to.
         */
        public void open(String filename) throws IOException{
                // Check to see if a file is open
                if(open){
                        // If file is already open then we should log that this went wrong
                        write(this.toString(), Logger.WARNING, "Open failed - a file is already open");
                }
                else{
                        this.filename = filename;
                        if(!fileCheck()) {
                                // Have to system.out.println errors because logging mechanism failed !
                                System.out.println(formatLogLine(toString(), "File check failed, construction terminated"));
                                throw new IOException("File check failed, unable to create FileLog");
                        }
                        try{
                                // Setup the writer
                                writer = new BufferedWriter(new FileWriter(filename, true));
                                // File is now open
                                open = true;
                        }
                        catch(IOException e){
                                System.out.println(formatLogLine(toString(), "Attempt to open writer failed - " + e.getMessage()));
                        }
                }
        }

        /**
         * The suspend() method halts writing to the file by setting the open
         * boolean to false, and thus blocking the write() method. A line is
         * written to the logfile beforehand to note that writing has been
         * suspended.
         */
        public void suspend(){
                // Check to see if a file is open
                if(open){
                        // Make a note of the fact that writing has been suspended
                        write(toString(), Logger.SYSMSG, "Writing suspended");
                        // Make sure writing not permitted
                        open=false;
                }
                else{
                        // If file is not open we should print this to the screen
                        System.out.println(formatLogLine(toString(), "Suspend failed - file not open"));
                }
        }
        
        /**
         * The resume() method resumes writing to the file by setting the open
         * boolean to true. A line is written to the logfile to signify this
         * event occuring.
         */
        public void resume(){
                // Check to see if a file is open
                if(open){
                        // If file is open we should print this to the screen
                        System.out.println(formatLogLine(toString(), "Resume failed - file open"));
                }
                else{
                        // Permit writing again
                        open=true;
                        // Make a note of the fact that writing has been resumed
                        write(toString(), Logger.SYSMSG, "Writing resumed");
                }
        }
    
    /**
     * Overrides the {@link java.lang.Object#toString() Object.toString()}
     * method to provide clean logging (every class should have this).
     *
     * This uses the uk.ac.ukc.iscream.util.FormatName class
     * to format the toString()
     *
     * @return the name of this class and its CVS revision
     */
    public String toString() {
        return FormatName.getName(
            _name,
            getClass().getName(),
            REVISION);
    }
    
//---PRIVATE METHODS---

        /**
         * This method generates a nicely formatted line for the log,
         * including the date/time and the source of the message. The date
         * and time are formatted using the DateFormat class, and the source
         * class is formatted using the toString() method found in every
         * source file. This is then prepended to the message and returned.
         * 
         * @param source A string representation of the calling object.
         * @param message The message to be logged.
         * @return The string to be written to the log.
         */
    private String formatLogLine(String source, String message){
        String date = DateFormat.getDateTimeInstance(DateFormat.SHORT, DateFormat.MEDIUM).format(new Date());
        return "[" + date + "] " + source + ": " + message;
    }

        /**
         * The fileCheck() method is used to ensure that writing is ok. It
         * performs so basic checks to make sure that if the file exists
         * it can be written to, and if not a new file is created. A boolean
         * result is returned to signify success or failure.
         * 
         * @return A boolean value signify whether the test was sucessful.
         */
    private boolean fileCheck(){
        boolean fileOK = false;
        try{
            File file = new File(filename);
                        
                        // File already exists
            if(file.exists()) {
                /* Only want success if it is a file (not a directory)
                                 * and can be written to.
                                 */
                                if(file.isFile() && file.canWrite()) {
                    fileOK = true;
                }
            }
                        // Create a new file and suceed
            else{
                file.createNewFile();
                fileOK = true;
            }
        }
        catch(IOException e){
            System.out.println(formatLogLine(toString(), "File check failed - "+e.getMessage()));
        }
        
        return fileOK;
    }

//---ACCESSOR/MUTATOR METHODS---

//---ATTRIBUTES---

        /**
         * The filename of the currently open, or last open, file.
         */
    private String filename;
        
    /**
         * The verbosity level of this instance
         */
        private int _verbosityLevel;
        
        /**
         * A reference to the writer being used.
         */
    private BufferedWriter writer;
        
        /**
         * A boolean signifying whether a file is open or not.
         */
        private boolean open = false;
        
        /**
     * This is the friendly identifier of the
     * component this class is running in.
     * eg, a Filter may be called "filter1",
     * If this class does not have an owning
     * component,  a name from the configuration
     * can be placed here.  This name could also
     * be changed to null for utility classes.
     */
    private String _name = Core.NAME;

//---STATIC ATTRIBUTES---
    
}
Revision:	1.4
Committed:	Mon Jan 22 12:01:46 2001 UTC (23 years, 3 months ago) by tdb
Branch:	MAIN
Changes since 1.3:	+3 -3 lines
Log Message:	* empty log message *
#	Content
1	//---PACKAGE DECLARATION---
2	package uk.ac.ukc.iscream.core.loggers;
3
4	//---IMPORTS---
5	import uk.ac.ukc.iscream.util.*;
6	import uk.ac.ukc.iscream.core.*;
7	import java.util.Date;
8	import java.text.DateFormat;
9	import java.util.Locale;
10	import java.io.BufferedWriter;
11	import java.io.File;
12	import java.io.FileWriter;
13	import java.io.IOException;
14
15	/**
16	* The FileLogger is an implementation of the LoggerImpl defined
17	* in the associated interface. It provides quite extensive features to allow
18	* logging ot a text file.
19	*
20	* @author $Author: ajm4 $
21	* @version $Id: FileLogger.java,v 1.3 2000/12/12 18:28:19 ajm4 Exp $
22	*/
23	public class FileLogger implements LoggerImpl {
24
25	//---FINAL ATTRIBUTES---
26
27	/**
28	* The current CVS revision of this class
29	*/
30	public final String REVISION = "$Revision: 1.3 $";
31
32	//---STATIC METHODS---
33
34	//---CONSTRUCTORS---
35
36	/**
37	* Creates a new FileLogger.
38	*
39	* The constructor checks that writing will be ok, then sets up the
40	* writer. It makes use of the fileCheck() method found later on to
41	* ensure writing will be ok, and throws an IOException if there is
42	* a problem. Errors at this stage cannot be logged because the
43	* logging mechanism has not be setup completely, so any problems
44	* are printed to the screen in the same format used for logging.
45	*
46	* @throws IOException if there is a problem with the file check.
47	*/
48	public FileLogger() throws IOException{
49	_verbosityLevel = Integer.parseInt(System.getProperty("uk.ac.ukc.iscream.Verbosity"));
50	filename = System.getProperty("uk.ac.ukc.iscream.LoggerClass.FileLogger.filename");
51	// Perform file check to make sure writing is ok
52	if(!fileCheck()){
53	// Have to system.out.println errors because logging mechanism failed !
54	System.out.println(formatLogLine(this.toString(), "File check failed, construction terminated"));
55	throw new IOException("File check failed, unable to create FileLog");
56	}
57	try{
58	// Setup the writer
59	writer = new BufferedWriter(new FileWriter(filename, true));
60	// File is now open
61	open = true;
62	}
63	catch(IOException e){
64	System.out.println(formatLogLine(toString(), "Attempt to setup writer failed - " + e.getMessage()));
65	}
66	// Put an initial line into the log
67	write(toString(), Logger.SYSINIT, "started");
68	write(toString(), Logger.SYSMSG, "using verbosity " + _verbosityLevel);
69	}
70
71	//---PUBLIC METHODS---
72
73	/**
74	* The write() method writes a line of log to the file, prepending
75	* it with some information about where to line came from and the
76	* date. This formatting is handled by the formatLogLine() method.
77	* There is some synchronisation here due to problems with the logfiles
78	* having multiple lines written on the same line, followed by dotted
79	* newlines in the wrong places. This is due to this method being
80	* called by multiple threads.
81	*
82	* @param source A string representation of the calling object.
83	* @param message The message to be logged.
84	*/
85	public synchronized void write(String source, int verbosity, String message) {
86	// Check to make sure file is open
87	if(open){
88	// Produce a nicely formatted line for the logfile
89	String line = formatLogLine(source, message);
90	try{
91	// We have to synchronize here due to problems with two write()'s being called before a newLine()
92	synchronized(writer){
93	// Attempt to write the line
94	writer.write(line);
95	// Best to use newLine() as it will use the correct platform encoding
96	writer.newLine();
97	}
98	// Make sure the line is written immeidiately
99	writer.flush();
100	}
101	catch(IOException e){
102	// We'd best log the error
103	System.out.println(formatLogLine(this.toString(), "Writing to logfile failed - " + e.getMessage()));
104	// As it's an IOException we should suspend logging
105	open = false;
106	}
107	}
108	else{
109	// If file is not open we should print this to the screen
110	System.out.println(formatLogLine(this.toString(), "Write failed - file not open"));
111	}
112	}
113
114	/**
115	* The clear() method erases the contents of the logfile. It does
116	* this in a very clumsy way - by closing the writer and opening a
117	* new one which is set not to append. This results in the logfile
118	* being overwritten, which effectively erases it.
119	*/
120	public void clear(){
121	// Check file is open
122	if(open){
123	write(toString(), Logger.SYSMSG, "Attempting to clear logfile");
124	try{
125	// Close appending writer
126	open = false;
127	writer.close();
128	// Open a non-appending writer
129	writer = new BufferedWriter(new FileWriter(filename));
130	open = true;
131	}
132	catch(IOException e){
133	// We'd best log the error
134	write(toString(), Logger.ERROR, "Attempt to clear logfile failed - "+e.getMessage());
135	// As it's an IOException we should suspend logging
136	open = false;
137	}
138	}
139	else{
140	// If file is not open we should print this to the screen
141	System.out.println(formatLogLine(toString(), "Clearing failed - file not open"));
142	}
143	}
144
145	/**
146	* The close() method closes the logfile and no more data can be written.
147	* If writing is attempted after close() has been called an error will be
148	* generated. The open() method can be used to reopen or open a new file.
149	*/
150	public void close(){
151	// Check to see if a file is open
152	if(open){
153	write(toString(), Logger.SYSMSG, "Attempting to terminate logging");
154	try{
155	open = false;
156	writer.close();
157	}
158	catch(IOException e){
159	write(toString(), Logger.ERROR, "Attempt to close logfile failed - " + e.getMessage());
160	// As it's an IOException we should suspend logging
161	open = false;
162	}
163	}
164	else{
165	// If file is not open we should print this to the screen
166	System.out.println(formatLogLine(toString(), "Close failed - file not open"));
167	}
168	}
169
170	/**
171	* The open() method opens a new file after the close() method has
172	* been called on the FileLog. This enables the user to easily change
173	* the file to which the log is being written. An error is generated
174	* if a file is already open.
175	*
176	* @param filename The new file to write to.
177	* @throws IOException if the file cannot be written to.
178	*/
179	public void open(String filename) throws IOException{
180	// Check to see if a file is open
181	if(open){
182	// If file is already open then we should log that this went wrong
183	write(this.toString(), Logger.WARNING, "Open failed - a file is already open");
184	}
185	else{
186	this.filename = filename;
187	if(!fileCheck()) {
188	// Have to system.out.println errors because logging mechanism failed !
189	System.out.println(formatLogLine(toString(), "File check failed, construction terminated"));
190	throw new IOException("File check failed, unable to create FileLog");
191	}
192	try{
193	// Setup the writer
194	writer = new BufferedWriter(new FileWriter(filename, true));
195	// File is now open
196	open = true;
197	}
198	catch(IOException e){
199	System.out.println(formatLogLine(toString(), "Attempt to open writer failed - " + e.getMessage()));
200	}
201	}
202	}
203
204	/**
205	* The suspend() method halts writing to the file by setting the open
206	* boolean to false, and thus blocking the write() method. A line is
207	* written to the logfile beforehand to note that writing has been
208	* suspended.
209	*/
210	public void suspend(){
211	// Check to see if a file is open
212	if(open){
213	// Make a note of the fact that writing has been suspended
214	write(toString(), Logger.SYSMSG, "Writing suspended");
215	// Make sure writing not permitted
216	open=false;
217	}
218	else{
219	// If file is not open we should print this to the screen
220	System.out.println(formatLogLine(toString(), "Suspend failed - file not open"));
221	}
222	}
223
224	/**
225	* The resume() method resumes writing to the file by setting the open
226	* boolean to true. A line is written to the logfile to signify this
227	* event occuring.
228	*/
229	public void resume(){
230	// Check to see if a file is open
231	if(open){
232	// If file is open we should print this to the screen
233	System.out.println(formatLogLine(toString(), "Resume failed - file open"));
234	}
235	else{
236	// Permit writing again
237	open=true;
238	// Make a note of the fact that writing has been resumed
239	write(toString(), Logger.SYSMSG, "Writing resumed");
240	}
241	}
242
243	/**
244	* Overrides the {@link java.lang.Object#toString() Object.toString()}
245	* method to provide clean logging (every class should have this).
246	*
247	* This uses the uk.ac.ukc.iscream.util.FormatName class
248	* to format the toString()
249	*
250	* @return the name of this class and its CVS revision
251	*/
252	public String toString() {
253	return FormatName.getName(
254	_name,
255	getClass().getName(),
256	REVISION);
257	}
258
259	//---PRIVATE METHODS---
260
261	/**
262	* This method generates a nicely formatted line for the log,
263	* including the date/time and the source of the message. The date
264	* and time are formatted using the DateFormat class, and the source
265	* class is formatted using the toString() method found in every
266	* source file. This is then prepended to the message and returned.
267	*
268	* @param source A string representation of the calling object.
269	* @param message The message to be logged.
270	* @return The string to be written to the log.
271	*/
272	private String formatLogLine(String source, String message){
273	String date = DateFormat.getDateTimeInstance(DateFormat.SHORT, DateFormat.MEDIUM).format(new Date());
274	return "[" + date + "] " + source + ": " + message;
275	}
276
277	/**
278	* The fileCheck() method is used to ensure that writing is ok. It
279	* performs so basic checks to make sure that if the file exists
280	* it can be written to, and if not a new file is created. A boolean
281	* result is returned to signify success or failure.
282	*
283	* @return A boolean value signify whether the test was sucessful.
284	*/
285	private boolean fileCheck(){
286	boolean fileOK = false;
287	try{
288	File file = new File(filename);
289
290	// File already exists
291	if(file.exists()) {
292	/* Only want success if it is a file (not a directory)
293	* and can be written to.
294	*/
295	if(file.isFile() && file.canWrite()) {
296	fileOK = true;
297	}
298	}
299	// Create a new file and suceed
300	else{
301	file.createNewFile();
302	fileOK = true;
303	}
304	}
305	catch(IOException e){
306	System.out.println(formatLogLine(toString(), "File check failed - "+e.getMessage()));
307	}
308
309	return fileOK;
310	}
311
312	//---ACCESSOR/MUTATOR METHODS---
313
314	//---ATTRIBUTES---
315
316	/**
317	* The filename of the currently open, or last open, file.
318	*/
319	private String filename;
320
321	/**
322	* The verbosity level of this instance
323	*/
324	private int _verbosityLevel;
325
326	/**
327	* A reference to the writer being used.
328	*/
329	private BufferedWriter writer;
330
331	/**
332	* A boolean signifying whether a file is open or not.
333	*/
334	private boolean open = false;
335
336	/**
337	* This is the friendly identifier of the
338	* component this class is running in.
339	* eg, a Filter may be called "filter1",
340	* If this class does not have an owning
341	* component, a name from the configuration
342	* can be placed here. This name could also
343	* be changed to null for utility classes.
344	*/
345	private String _name = Core.NAME;
346
347	//---STATIC ATTRIBUTES---
348
349	}