synchronization with executorService

Question

i wrote tthe below method to insert records using threads, but at run time i receive "[SQLITE_BUSY] The database file is locked (database is locked)" error,and i think could be due to conflict of sqlite statement.

i just want to know i am wusing the executorservice correctly in the "insertRecord" method? is there any other variables shoule have been synchronizedß

code :

public void insertRecord(String nodeID, String lat, String lng, String xmlpath) throws SQLException, ClassNotFoundException {

    if (this.isTableExists(this.TABLE_NAME)) {

        InsertRun insRun = new InsertRun(this.psInsert, nodeID, lat, lng, xmlpath);
        this.executor.execute(insRun);

    } else {
        Log.e(TAG, "insertRecord", "table: ["+this.TABLE_NAME+"] does not exist");
    }
}

public void flush() throws SQLException {
    this.psInsert.executeBatch();

    this.psInsert.close();
    this.connInsert.close();

    Log.d(TAG, "insertRecord", "the rest of the records flushed into data base table.");
}

private class InsertRun implements Runnable {

    private PreparedStatement psInsert = null;
    private String nodeID;
    private String lat;
    private String lng;
    private String xmlPath;

    public InsertRun(PreparedStatement psInsert, String nodeID, String lat, String lng, String xmlpath) {
        // TODO Auto-generated constructor stub
        this.psInsert = psInsert;
        this.nodeID = nodeID;
        this.lat = lat;
        this.lng = lng;
        this.xmlPath = xmlpath;
    }

    @Override
    public void run() {
        // TODO Auto-generated method stub
        try {
            this.psInsert.setString(1, this.nodeID);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        try {
            this.psInsert.setString(2, this.lat);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        try {
            this.psInsert.setString(3, this.lng);
        } catch (SQLException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
        try {
            this.psInsert.setString(4, this.xmlPath);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        try {
            this.psInsert.addBatch();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        synchronized(this) {
            if (++batchCnt == SysConsts.BATCH_SIZE) {
                try {
                    this.psInsert.executeBatch();
                } catch (SQLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }

                batchCnt = 0;

                Log.d(TAG, "InsertRun", SysConsts.BATCH_SIZE+" records inserted.");
            }
        }

    }

}

Answer 1

SQLite is not a database suitable for concurrent access. You cannot modify your database concurrently:

Multiple processes can have the same database open at the same time. Multiple processes can be doing a SELECT at the same time. But only one process can be making changes to the database at any moment in time, however.

.

When SQLite tries to access a file that is locked by another process, the default behavior is to return SQLITE_BUSY

Read this for details (and simply give up multithreading in your app...)

Answer 2

Additionally, good concurrency design considerations can be difficult to offer without know alot more about the program. Suggest perusing through Java Concurrency in Practice if you plan on writing more multi-threaded applications.