Jackcess DatabaseBuilder.open fails

问题

I am using Jackcess API in my Eclipse plugin project. I added jackcess-2.1.0.jar file under resources/lib. I included the jar under my Binary build and in build.properties. I successfully make a connection using connection string but my DatabaseBuilder.open() call is not executing. My code is

 public void run() {
    try {
        File tempTarget = File.createTempFile("eap-mirror", "eap");
        try {
            this.source = DriverManager.getConnection(EaDbStringParser.eaDbStringToJdbc(sourceString));
            this.source.setReadOnly(true);

            try {
                FileUtils.copyFile(new File(templateFileString), tempTarget);
            } catch (IOException e) {
                e.printStackTrace();
            }
            // Changes
            try {
                this.target = DatabaseBuilder.open(tempTarget);
            } catch (IOException e) {
                e.printStackTrace();
            }

            Collection<String> tables = selectTables(source);
            long time = System.currentTimeMillis();
            for (String tableName : tables) {
                long tTime = System.currentTimeMillis();
                Table table = target.getTable(tableName);
                System.out.print("Mirroring table " + tableName + "...");
                table.setOverrideAutonumber(true);

                copyTable(table, source, target);
                System.out.println(" took "+ (System.currentTimeMillis() - tTime));
            }
            System.out.println("Done. Overall time: "+ (System.currentTimeMillis() - time));
            System.out.println("done");
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {

          // More Code here

  } catch (IOException e1) {

    }
}

When I run the class in debug mode and I reach DatabaseBuilder.open call it fails.

Here is my project structure:

Can anyone tell me the possible reason for it ?

回答1:

The .open method of DatabaseBuilder expects to open an existing well-formed Access database file. The .createTempFile method of java.io.File creates a 0-byte file. So, the code

File dbFile;
try {
    dbFile = File.createTempFile("eap-mirror", "eap");
    try (Database db = DatabaseBuilder.open(dbFile)) {
        System.out.println(db.getFileFormat());
    } catch (IOException ioe) {
        ioe.printStackTrace(System.out);
    }
} catch (Exception e) {
    e.printStackTrace(System.out);
} finally {
    System.out.println("Finally...");
}

will cause Jackcess to throw

java.io.IOException: Empty database file

when it tries to do DatabaseBuilder.open(dbFile).

Instead, you should DatabaseBuilder.create to convert the 0-byte file into a real Access database file like this

File dbFile;
try {
    dbFile = File.createTempFile("eap-mirror", ".accdb");
    dbFile.deleteOnExit();
    try (Database db = DatabaseBuilder.create(Database.FileFormat.V2010, dbFile)) {
        System.out.println(db.getFileFormat());
    } catch (IOException ioe) {
        ioe.printStackTrace(System.out);
    }
} catch (Exception e) {
    e.printStackTrace(System.out);
} finally {
    System.out.println("Finally...");
}

来源：https://stackoverflow.com/questions/29844258/jackcess-databasebuilder-open-fails

标签

java

eclipse-plugin

jackcess