Java-覆盖抽象方法

Question

I want to develop logging system in OSGI bundle which can write application errors into file on the HDD.

This is the Activator:

import org.osgi.framework.BundleActivator;
import org.osgi.framework.BundleContext;
import org.osgi.framework.Constants;
import org.osgi.framework.Filter;
import org.osgi.framework.ServiceReference;
import org.osgi.framework.ServiceRegistration;
import org.osgi.util.tracker.ServiceTracker;


public class LoggingSystemApp implements BundleActivator {

    LoggingSystemImpl log = null;

    @Override
    public void start(final BundleContext bc) throws Exception {
        debug("Activator started");


        ServiceRegistration registerService = bc.registerService(LoggingSystemImpl.class.getName(), new LoggingSystemImpl(), new Properties());
          /* Start Logger System */
          log = LoggingSystemImpl.getInstance();
          log.start();       


    }

    public void stop(BundleContext bc) throws Exception {
        boolean ungetService = bc.ungetService(bc.getServiceReference(LoggingSystem.class.getName()));
        st.close();

        log.stop();
    }

    private void debug(String msg) {
        System.out.println("JDBCBundleActivator: " + msg);
    }

}

This is the implementation of the Logging system:

import java.io.BufferedWriter;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.nio.charset.Charset;
import java.sql.Connection;
import javax.sql.DataSource;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Calendar;
import java.util.Locale;
import org.DX_57.osgi.LS_27.api.LoggingSystem;

public class LoggingSystemImpl implements LoggingSystem {

       public LoggingSystemImpl() {
       }

       public DataSource ds;

       @Override
       public void setDataSource(DataSource ds){
           this.ds = ds;
       }


        private final static Calendar calendar = Calendar.getInstance();
        private final static String user = System.getenv("USERNAME").toLowerCase();
        private final static String sMonth = calendar.getDisplayName(Calendar.MONTH, Calendar.LONG, Locale.ENGLISH);
        private final static int y = calendar.get(Calendar.YEAR);

        // the name of the log file
        //private final String logName = sysDrive + "\\fttb_web - " + sMonth.toLowerCase() + ", " + y + ".log";
        private final String logName = "logger - " + sMonth.toLowerCase() + ", " + y + ".log";

        private static boolean closed;
        private static LoggingSystemImpl log = null;
        private static BufferedWriter bw = null;
        private static FileOutputStream fos = null;
        private static OutputStreamWriter osw = null;


        /* Utilialize Buffer and wait for data to write */
        public void start() throws IOException{            
            log = LoggingSystemImpl.getInstance();
        }

        public void stop(){            
            log.close();           
        }

        public void WriteLog(String WriteString){
            log.writeln(WriteString);            
        }

        public void LoggingSystemImpl() throws IOException
        {
            fos = new FileOutputStream(logName, true);

            // set encoding to cyrillic (if available)
            if (Charset.isSupported("windows-1251"))
            {
                osw = new OutputStreamWriter(fos, Charset.forName("windows-1251"));
            }
            else { osw = new OutputStreamWriter(fos); }

            bw = new BufferedWriter(osw, 2048); // 2Mb buffer


        }

        // intro header for log session
        public static synchronized LoggingSystemImpl getInstance() throws IOException
        {
            boolean exc = false;
            try
            {
                if (log == null || closed)
                {
                    log = new LoggingSystemImpl();
                    closed = false;
                    log.writeln("logged in.");
                    log.nl();
                }
            }
    //      catch(IOException x) { exc = true; throw x; }
            catch(Exception x) { exc = true; x.printStackTrace(); }
            finally
            {
                if (exc)
                {
                    try
                    {
                        if (fos != null) { fos.close(); fos = null; }
                        if (osw != null) { osw.close(); fos = null; }
                        if (bw != null)  { bw.close(); bw = null; }
                    }
                    catch(Exception x) { x.printStackTrace(); }
                }
            }
            return log;
        }


        public synchronized void nl()
        {
            try { bw.newLine(); }
            catch(IOException x) {x.printStackTrace();}
        }

        public synchronized void nl(int count)
        {
            try
            {
                for (int i = 0; i < count; i++) bw.newLine();
            }
            catch(IOException x) {x.printStackTrace();}
        }
        public synchronized void writeln(String s)
        {
            try { bw.write(getTime() + ": " + s); bw.newLine(); }
            catch(IOException x) {x.printStackTrace();}
        }

        public synchronized void write(String s)
        {
            try { bw.write(s); }
            catch (IOException x) {x.printStackTrace();}
        }

        public synchronized void close()
        {
            try
            {
                if (bw != null)
                {
                    writeln("logged out.");
                    nl();
                    bw.flush();
                    bw.close();
                    closed = true;

                    fos = null;
                    osw = null;
                    bw = null;
                }
            }
            catch(IOException x) { x.printStackTrace(); }

        }

        public synchronized boolean isClosed() { return closed; }

        public synchronized void writeException(Exception x)
        {
            writeln("");
            write("\t" + x.toString()); nl();
            StackTraceElement[] ste = x.getStackTrace();
            int j = 0;
            for (int i = 0; i < ste.length; i++)
            {

                if (i < 15) { write("\t\tat " + ste[i].toString()); nl(); }
                else { j++; }

            }

            if (j > 0) { write("\t\t... " + j + " more"); nl(); }

            nl(2);
        }

        private String getTime()
        {
            Calendar c = Calendar.getInstance();
            int month = c.get(Calendar.MONTH) + 1;

            int d = c.get(Calendar.DAY_OF_MONTH);
            int h = c.get(Calendar.HOUR_OF_DAY);

            int m = c.get(Calendar.MINUTE);
            int s = c.get(Calendar.SECOND);
            int y = c.get(Calendar.YEAR);

            String dd = d < 10 ? "0"+d : ""+d;
            String hh = h < 10 ? "0"+h : ""+h;
            String mm = m < 10 ? "0"+m : ""+m;
            String ss = s < 10 ? "0"+s : ""+s;
            String sm = month < 10 ? "0"+month : ""+month;

            return user + " [" + y + "." + sm + "." + dd + " " + hh +  ":" + mm +  ":" + ss + "]";
        }         



}

When I try to compile the code in Netbeans I get this error:

COMPILATION ERROR : 
-------------------------------------------------------------
org/DX_57/osgi/LS_27/impl/LoggingSystemImpl.java:[34,7] error: LoggingSystemImpl is not abstract and does not override abstract method SessionRegister(String,String,String) in LoggingSystem
1 error

How I can fix this problem?

Best wishes

PS this is the code of the interface

public interface LoggingSystem {

        public void setDataSource(DataSource ds);


}

EDIT Can you tell me do you see any other errors in the code especially the Activator class?

Answer 1

You have to implement the mentioned method in your class. The message says that your class is not abstract bus has not concretely implemented all abstract methods from its parents.

Answer 2

Well, the error message is pretty clear. You can either declare LoggingSystemImpl as abstract or implement the missing method - SessionRegister(String,String,String) .

The reason for this is that the interface LoggingSystem has the method SessionRegister(String,String,String) declared. Because it has no implementation, it needs to be implemented in all non-abstract children, including your class.

A quick fix would be:

public class LoggingSystemImpl implements LoggingSystem {
   void SessionRegister(String,String,String) 
   { //dummy implementation
   }
   //other methods
}

Answer 3

好像在接口中声明了尚未实现的SessionRegister(String,String,String)方法...您可能应该实现它...

Answer 4

My guess is that if you declared LoggingSystem as you show in your code, then the import in the implementation class is the problem:

import org.DX_57.osgi.LS_27.api.LoggingSystem;

Are you sure that's the interface you're trying to implement?