core/loggers/FileLogger.java

//---PACKAGE DECLARATION---
package uk.org.iscream.core.loggers;

//---IMPORTS---
import uk.org.iscream.util.*;
import uk.org.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: tdb1 $
 * @version $Id: FileLogger.java,v 1.7 2001/02/25 20:49:20 tdb1 Exp $
 */
public class FileLogger implements LoggerImpl {

//---FINAL ATTRIBUTES---

    /**
     * The current CVS revision of this class
     */
    public final String REVISION = "$Revision: 1.7 $";
    
//---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{
        filename = System.getProperty("uk.org.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(FormatName.formatLogLine(this.toString(), Logger.FATAL, "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(FormatName.formatLogLine(this.toString(), Logger.FATAL, "Attempt to setup writer failed - " + e.getMessage()));
        }
                // Put an initial line into the log
        write(toString(), Logger.SYSINIT, "started");
    }

//---PUBLIC METHODS---
    
    /**
         * The write() method takes a line of text, pre-formatted
         * and outputs it using a method defined by the actual
         * implementation. The verbosity is given in case the
         * implementation wishes to utilise it in the layout -
         * eg. a different colour or font.
         * 
         * This instance writes the line to a file.
         *
         * @param line A line of formatted text to be logged
         * @param verbosity the verbosity of this message
         */  
    public synchronized void write(String line, int verbosity) {
                // Check to make sure file is open
                if(open){
                        // Produce a nicely formatted line for the logfile
                        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(FormatName.formatLogLine(this.toString(), Logger.FATAL, "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(FormatName.formatLogLine(this.toString(), Logger.FATAL, "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(FormatName.formatLogLine(this.toString(), Logger.FATAL, "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(FormatName.formatLogLine(this.toString(), Logger.FATAL, "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(FormatName.formatLogLine(this.toString(), Logger.FATAL, "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(FormatName.formatLogLine(this.toString(), Logger.FATAL, "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(FormatName.formatLogLine(this.toString(), Logger.FATAL, "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(FormatName.formatLogLine(this.toString(), Logger.FATAL, "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.org.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---

        /**
         * 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(FormatName.formatLogLine(this.toString(), Logger.FATAL, "File check failed - "+e.getMessage()));
        }
        
        return fileOK;
    }

    /**
     * This method is provided if this class wishes to log
     * a message itself.
     *
         * @param source A String representation of the source
         * @param verbosity the verbosity of this message
         * @param message The message to log
         */  
    private void write(String source, int verbosity, String message) {
        write(FormatName.formatLogLine(source, verbosity, message), verbosity);
    }

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

//---ATTRIBUTES---

        /**
         * The filename of the currently open, or last open, file.
         */
    private String filename;
        
        /**
         * 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:	1.8
Committed:	Wed Mar 14 23:25:29 2001 UTC (23 years, 2 months ago) by tdb
Branch:	MAIN
CVS Tags:	PROJECT_COMPLETION
Changes since 1.7:	+7 -7 lines
Log Message:	The whole server package structure has been changed. Old Package: uk.ac.ukc.iscream.* New Package: uk.org.iscream.*
#	User	Rev	Content
1	tdb	1.1	//---PACKAGE DECLARATION---
2	tdb	1.8	package uk.org.iscream.core.loggers;
3	tdb	1.1
4			//---IMPORTS---
5	tdb	1.8	import uk.org.iscream.util.*;
6			import uk.org.iscream.core.*;
7	tdb	1.1	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	tdb	1.5	* @author $Author: tdb1 $
21	tdb	1.8	* @version $Id: FileLogger.java,v 1.7 2001/02/25 20:49:20 tdb1 Exp $
22	tdb	1.1	*/
23	tdb	1.4	public class FileLogger implements LoggerImpl {
24	tdb	1.1
25			//---FINAL ATTRIBUTES---
26
27			/**
28			* The current CVS revision of this class
29			*/
30	tdb	1.8	public final String REVISION = "$Revision: 1.7 $";
31	tdb	1.1
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	tdb	1.8	filename = System.getProperty("uk.org.iscream.LoggerClass.FileLogger.filename");
50	tdb	1.1	// Perform file check to make sure writing is ok
51			if(!fileCheck()){
52			// Have to system.out.println errors because logging mechanism failed !
53	tdb	1.6	System.out.println(FormatName.formatLogLine(this.toString(), Logger.FATAL, "File check failed, construction terminated"));
54	tdb	1.1	throw new IOException("File check failed, unable to create FileLog");
55			}
56			try{
57			// Setup the writer
58			writer = new BufferedWriter(new FileWriter(filename, true));
59			// File is now open
60			open = true;
61			}
62			catch(IOException e){
63	tdb	1.6	System.out.println(FormatName.formatLogLine(this.toString(), Logger.FATAL, "Attempt to setup writer failed - " + e.getMessage()));
64	tdb	1.1	}
65			// Put an initial line into the log
66	ajm	1.3	write(toString(), Logger.SYSINIT, "started");
67	tdb	1.1	}
68
69			//---PUBLIC METHODS---
70
71	tdb	1.7	/**
72			* The write() method takes a line of text, pre-formatted
73			* and outputs it using a method defined by the actual
74			* implementation. The verbosity is given in case the
75			* implementation wishes to utilise it in the layout -
76			* eg. a different colour or font.
77	tdb	1.1	*
78	tdb	1.7	* This instance writes the line to a file.
79			*
80			* @param line A line of formatted text to be logged
81			* @param verbosity the verbosity of this message
82			*/
83	tdb	1.6	public synchronized void write(String line, int verbosity) {
84			// Check to make sure file is open
85			if(open){
86			// Produce a nicely formatted line for the logfile
87			try{
88			// We have to synchronize here due to problems with two write()'s being called before a newLine()
89			synchronized(writer){
90			// Attempt to write the line
91			writer.write(line);
92			// Best to use newLine() as it will use the correct platform encoding
93			writer.newLine();
94			}
95			// Make sure the line is written immeidiately
96			writer.flush();
97			}
98			catch(IOException e){
99			// We'd best log the error
100			System.out.println(FormatName.formatLogLine(this.toString(), Logger.FATAL, "Writing to logfile failed - " + e.getMessage()));
101			// As it's an IOException we should suspend logging
102			open = false;
103			}
104			}
105			else{
106			// If file is not open we should print this to the screen
107			System.out.println(FormatName.formatLogLine(this.toString(), Logger.FATAL, "Write failed - file not open"));
108			}
109	tdb	1.1	}
110
111			/**
112			* The clear() method erases the contents of the logfile. It does
113			* this in a very clumsy way - by closing the writer and opening a
114			* new one which is set not to append. This results in the logfile
115			* being overwritten, which effectively erases it.
116			*/
117			public void clear(){
118			// Check file is open
119			if(open){
120	ajm	1.3	write(toString(), Logger.SYSMSG, "Attempting to clear logfile");
121	tdb	1.1	try{
122			// Close appending writer
123			open = false;
124			writer.close();
125			// Open a non-appending writer
126			writer = new BufferedWriter(new FileWriter(filename));
127			open = true;
128			}
129			catch(IOException e){
130			// We'd best log the error
131	ajm	1.3	write(toString(), Logger.ERROR, "Attempt to clear logfile failed - "+e.getMessage());
132	tdb	1.1	// As it's an IOException we should suspend logging
133			open = false;
134			}
135			}
136			else{
137			// If file is not open we should print this to the screen
138	tdb	1.6	System.out.println(FormatName.formatLogLine(this.toString(), Logger.FATAL, "Clearing failed - file not open"));
139	tdb	1.1	}
140			}
141
142			/**
143			* The close() method closes the logfile and no more data can be written.
144			* If writing is attempted after close() has been called an error will be
145			* generated. The open() method can be used to reopen or open a new file.
146			*/
147			public void close(){
148			// Check to see if a file is open
149			if(open){
150	ajm	1.3	write(toString(), Logger.SYSMSG, "Attempting to terminate logging");
151	tdb	1.1	try{
152			open = false;
153			writer.close();
154			}
155			catch(IOException e){
156	ajm	1.3	write(toString(), Logger.ERROR, "Attempt to close logfile failed - " + e.getMessage());
157	tdb	1.1	// As it's an IOException we should suspend logging
158			open = false;
159			}
160			}
161			else{
162			// If file is not open we should print this to the screen
163	tdb	1.6	System.out.println(FormatName.formatLogLine(this.toString(), Logger.FATAL, "Close failed - file not open"));
164	tdb	1.1	}
165			}
166
167			/**
168			* The open() method opens a new file after the close() method has
169			* been called on the FileLog. This enables the user to easily change
170			* the file to which the log is being written. An error is generated
171			* if a file is already open.
172			*
173			* @param filename The new file to write to.
174			* @throws IOException if the file cannot be written to.
175			*/
176			public void open(String filename) throws IOException{
177			// Check to see if a file is open
178			if(open){
179			// If file is already open then we should log that this went wrong
180	ajm	1.3	write(this.toString(), Logger.WARNING, "Open failed - a file is already open");
181	tdb	1.1	}
182			else{
183			this.filename = filename;
184			if(!fileCheck()) {
185			// Have to system.out.println errors because logging mechanism failed !
186	tdb	1.6	System.out.println(FormatName.formatLogLine(this.toString(), Logger.FATAL, "File check failed, construction terminated"));
187	tdb	1.1	throw new IOException("File check failed, unable to create FileLog");
188			}
189			try{
190			// Setup the writer
191			writer = new BufferedWriter(new FileWriter(filename, true));
192			// File is now open
193			open = true;
194			}
195			catch(IOException e){
196	tdb	1.6	System.out.println(FormatName.formatLogLine(this.toString(), Logger.FATAL, "Attempt to open writer failed - " + e.getMessage()));
197	tdb	1.1	}
198			}
199			}
200
201			/**
202			* The suspend() method halts writing to the file by setting the open
203			* boolean to false, and thus blocking the write() method. A line is
204			* written to the logfile beforehand to note that writing has been
205			* suspended.
206			*/
207			public void suspend(){
208			// Check to see if a file is open
209			if(open){
210			// Make a note of the fact that writing has been suspended
211	ajm	1.3	write(toString(), Logger.SYSMSG, "Writing suspended");
212	tdb	1.1	// Make sure writing not permitted
213			open=false;
214			}
215			else{
216			// If file is not open we should print this to the screen
217	tdb	1.6	System.out.println(FormatName.formatLogLine(this.toString(), Logger.FATAL, "Suspend failed - file not open"));
218	tdb	1.1	}
219			}
220
221			/**
222			* The resume() method resumes writing to the file by setting the open
223			* boolean to true. A line is written to the logfile to signify this
224			* event occuring.
225			*/
226			public void resume(){
227			// Check to see if a file is open
228			if(open){
229			// If file is open we should print this to the screen
230	tdb	1.6	System.out.println(FormatName.formatLogLine(this.toString(), Logger.FATAL, "Resume failed - file open"));
231	tdb	1.1	}
232			else{
233			// Permit writing again
234			open=true;
235			// Make a note of the fact that writing has been resumed
236	ajm	1.3	write(toString(), Logger.SYSMSG, "Writing resumed");
237	tdb	1.1	}
238			}
239
240			/**
241			* Overrides the {@link java.lang.Object#toString() Object.toString()}
242			* method to provide clean logging (every class should have this).
243			*
244	tdb	1.8	* This uses the uk.org.iscream.util.FormatName class
245	ajm	1.3	* to format the toString()
246			*
247	tdb	1.1	* @return the name of this class and its CVS revision
248			*/
249			public String toString() {
250	ajm	1.3	return FormatName.getName(
251			_name,
252			getClass().getName(),
253			REVISION);
254	tdb	1.1	}
255
256			//---PRIVATE METHODS---
257
258			/**
259			* The fileCheck() method is used to ensure that writing is ok. It
260			* performs so basic checks to make sure that if the file exists
261			* it can be written to, and if not a new file is created. A boolean
262			* result is returned to signify success or failure.
263			*
264			* @return A boolean value signify whether the test was sucessful.
265			*/
266			private boolean fileCheck(){
267			boolean fileOK = false;
268			try{
269			File file = new File(filename);
270
271			// File already exists
272			if(file.exists()) {
273			/* Only want success if it is a file (not a directory)
274			* and can be written to.
275			*/
276			if(file.isFile() && file.canWrite()) {
277			fileOK = true;
278			}
279			}
280			// Create a new file and suceed
281			else{
282			file.createNewFile();
283			fileOK = true;
284			}
285			}
286			catch(IOException e){
287	tdb	1.6	System.out.println(FormatName.formatLogLine(this.toString(), Logger.FATAL, "File check failed - "+e.getMessage()));
288	tdb	1.1	}
289
290			return fileOK;
291			}
292
293	tdb	1.7	/**
294			* This method is provided if this class wishes to log
295			* a message itself.
296			*
297			* @param source A String representation of the source
298			* @param verbosity the verbosity of this message
299			* @param message The message to log
300			*/
301	tdb	1.6	private void write(String source, int verbosity, String message) {
302			write(FormatName.formatLogLine(source, verbosity, message), verbosity);
303			}
304
305	tdb	1.1	//---ACCESSOR/MUTATOR METHODS---
306
307			//---ATTRIBUTES---
308
309			/**
310			* The filename of the currently open, or last open, file.
311			*/
312			private String filename;
313
314			/**
315			* A reference to the writer being used.
316			*/
317			private BufferedWriter writer;
318
319			/**
320			* A boolean signifying whether a file is open or not.
321			*/
322			private boolean open = false;
323	ajm	1.3
324			/**
325			* This is the friendly identifier of the
326			* component this class is running in.
327			* eg, a Filter may be called "filter1",
328			* If this class does not have an owning
329			* component, a name from the configuration
330			* can be placed here. This name could also
331			* be changed to null for utility classes.
332			*/
333			private String _name = Core.NAME;
334	tdb	1.1
335			//---STATIC ATTRIBUTES---
336
337			}