Examples of org.apache.empire.db.DBReader

org.apache.empire.db.DBReader
This class is used to perform database queries from a DBCommand object and access the results.
In oder to perform a query call the open() function or - for single row queries - call getRecordData();
You can iterate through the rows using moveNext() or an iterator.

However take care: A reader must always be explicitly closed using the close() method!
Otherwise you may lock the JDBC connection and run out of resources.
Use
```
try { ... } finally { reader.close(); } 
```
to make sure the reader is closed.

To access and work with the query result you can do one of the following:
- access field values directly by using one of the get... functions (see {@link DBRecordData})
- get the rows as a list of Java Beans using by using {@link DBReader#getBeanList(Class,int)}
- get the rows as an XML-Document using {@link DBReader#getXmlDocument()}
- initialize a DBRecord with the current row data using {@link DBReader#initRecord(DBRowSet,DBRecord)}
  This will allow you to modify and update the data.

    }


    // SupplierReader
    public boolean initBeanList(DBCommand cmd)
    {
        DBReader reader = new DBReader();
        try {
            // Open Suppier Reader
            if (!reader.open(cmd, action.getConnection() ))
            {   return error(reader);
            }
            // Move to desired Position
            int first = this.getFirstItemIndex();
            if (first>0 && !reader.skipRows(first))
            {   // Page is not valid. Try again from beginning
                reader.close();
                setFirstItem(0);
                return initBeanList(cmd);
            }
            // Read List
            list = reader.getBeanList(beanClass, getPageSize());
            if (list==null)
            {   return error(reader);
            }
            // done
            return true;
            
        } finally {
            reader.close();
        }
    }

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            comp = comp.and(T_EMP.DEPARTMENT_ID.is(department));
        }


        cmd.where(comp);


        DBReader reader = new DBReader();
        reader.open(cmd, conn);
        List<Employee> lst = reader.getBeanList(Employee.class);
        return lst;
    }

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    public List<Department> getDepartments()
    {
        DBCommand cmd = db.createCommand();
        cmd.select(T_DEP.getColumns());


        DBReader reader = new DBReader();
        reader.open(cmd, conn);
        return reader.getBeanList(Department.class);
    }

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        // Set constraints and order
        cmd.where(EMP.LASTNAME.length().isGreaterThan(0));
        cmd.orderBy(EMP.LASTNAME, EMP.FIRSTNAME);


    // Query Records and print output
    DBReader reader = new DBReader();
    try
        {
      // Open Reader
      System.out.println("Running Query:");
      System.out.println(cmd.getSelect());
      reader.open(cmd, conn);
      // Print output
      System.out.println("---------------------------------");
      switch(type)
      {
          case BeanList:
              // Text-Output by iterating through all records.
                  while (reader.moveNext())
                    {
                      System.out.println(reader.getString(EMP.EMPLOYEE_ID)
                              + "\t" + reader.getString(EMPLOYEE_FULLNAME)
                              + "\t" + EMP.GENDER.getOptions().get(reader.getString(EMP.GENDER))
                                + "\t" + reader.getString(PHONE_EXT_NUMBER)
                              + "\t" + reader.getString(DEP.NAME));
                  }
              break;
                case Reader:
                    // Text-Output using a list of Java Beans supplied by the DBReader
                    List<SampleBean> beanList = reader.getBeanList(SampleBean.class);
                    System.out.println(String.valueOf(beanList.size()) + " SampleBeans returned from Query.");
                    for (SampleBean b : beanList)
                    {
                        System.out.println(b.toString());
                    }
                    break;
                case XmlDocument:
                    // XML Output
                    Document doc = reader.getXmlDocument();
                    // Print XML Document to System.out
                    XMLWriter.debug(doc);
                    break;
      }


    } finally
        {
      // always close Reader
      reader.close();
    }
    }

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        Connection conn = getConnection();


        DBCommand cmd = db.createCommand();
        cmd.select(table.getColumns());
        cmd.where(table.getPrimaryKey().getColumns()[0].is(pk)); //i know there is just one pk-column ;-)
        DBReader reader = openReader(cmd, conn);
        Map<Object, Object> dep = null;
        if (reader.moveNext()) {
            dep = new HashMap<Object, Object>();
            for (DBColumn col : table.getColumns()) {
                dep.put(col.getName(), reader.getValue(col));
            }
        }
        reader.close();
        return dep;
    }

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    db.open(driver, conn);
    DBCommand cmd = db.createCommand();
    cmd.select(EMP.EMPLOYEE_ID, EMP.FIRSTNAME);


    int rowCount = 0;
    DBReader reader = new DBReader();
    try {
      System.err.println(cmd.getSelect());
      boolean succes = reader.open(cmd, conn);
      assertTrue(db.getErrorMessage(), succes);
      while (reader.moveNext()) {
        rowCount++;
        System.out.println(reader.getString(EMP.EMPLOYEE_ID) + "\t" + reader.getString(EMP.FIRSTNAME));
      }
    } finally {
      reader.close();
    }
    
    assertEquals("We expect 3 rows", 3, rowCount);


  }

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        cmd.select(T_EMP.getColumns());
        // Set Constraints
        cmd.where(T_EMP.C_RETIRED.is(false));


        // Query Records and print output
        DBReader reader = new DBReader();
        try
        {
            // Open Reader
            System.out.println("Running Query:");
            System.out.println(cmd.getSelect());
            if (reader.open(cmd, conn) == false)
                throw new RuntimeException(reader.getErrorMessage());
            // Print output
            DBRecord record = new DBRecord();
            while (reader.moveNext())
            {
                // Calculate sum
                int sum = 0;
                for (int i=0; i<reader.getFieldCount(); i++)
                    sum += calcCharSum(reader.getString(i));
                // Init updateable record
                reader.initRecord(EMP, record);
                // reader
                record.setValue(T_EMP.C_CHECKSUM, sum);
                record.update(conn);
            }
            // Done
            db.commit(conn);


        } finally
        {
            // always close Reader
            reader.close();
        }
    }

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        cmd.select(T_EMP.getColumns());
        // Set Constraints
        cmd.where(T_EMP.C_RETIRED.is(false));


        // Query Records and print output
        DBReader reader = new DBReader();
        try
        {   // Open Reader
            System.out.println("Running Query:");
            System.out.println(cmd.getSelect());
            if (reader.open(cmd, conn) == false)
                throw new RuntimeException(reader.getErrorMessage());
            // Print output
            HashMap<Integer, DBRecord> employeeMap = new HashMap<Integer, DBRecord>();
            while (reader.moveNext())
            {
                DBRecord rec = new DBRecord();
                reader.initRecord(T_EMP, rec);
                employeeMap.put(reader.getInt(T_EMP.C_EMPLOYEE_ID), rec);
            }
            return employeeMap;


        } finally
        {   // always close Reader
            reader.close();
        }
    }

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     * @param conn the connection
     */
    private static void printQueryResults(DBCommand cmd, Connection conn)
    {
        // Query Records and print output
        DBReader reader = new DBReader();
        try
        {   // Open Reader
            System.out.println("Running Query:");
            System.out.println(cmd.getSelect());
            if (reader.open(cmd, conn) == false)
                throw new RuntimeException(reader.getErrorMessage());
            // Print column titles 
            System.out.println("---------------------------------");
            int count = reader.getFieldCount();
            for (int i=0; i<count; i++)
            {   // Print all column names
                DBColumnExpr c = reader.getColumnExpr(i);
                if (i>0)
                    System.out.print("\t");
                System.out.print(c.getName());
            }
            // Print output
            System.out.println("");
            // Text-Output by iterating through all records.
            while (reader.moveNext())
            {
                for (int i=0; i<count; i++)
                {   // Print all field values
                    if (i>0)
                        System.out.print("\t");
                    // Check if conversion is necessary
                    DBColumnExpr c = reader.getColumnExpr(i);
                    Options opt = c.getOptions();
                    if (opt!=null)
                    {   // Option Lookup
                        System.out.print(opt.get(reader.getValue(i)));
                    }
                    else
                    {   // Print String
                        System.out.print(reader.getString(i));
                    }
                }
                System.out.println("");
            }


        } finally
        {   // always close Reader
            reader.close();
        }
    }

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    private void loadItems(boolean initScrollbar)
    {
        // DBReader
        BeanListTableInfo lti = (BeanListTableInfo) getTableInfo();
        DBReader r = new DBReader();
        try
        { // Check command
            DBCommand queryCmd = lti.getQueryCmd();
            if (queryCmd == null)
                throw new ObjectNotValidException(this);


            boolean loadPageFromPosition = lti.isValid() && lti.isAllowPagination();
            lti.setValid(false);


            if (lti.isSortOrderChanged())
            { // Set Sort order
                setOrderBy(queryCmd);
                lti.setSortOrderChanged(false);
            }


            // DBReader.open immer nur innerhalb eines try {} finally {} blocks!
            r.open(queryCmd, getConnection(queryCmd));


            // get position from the session
            int position = 0;
            int maxItems = 1000;
            if (loadPageFromPosition)
            {
                position = lti.getPosition();
                if (position < 0)
                { // position < 0 is not possible, set to 0
                    position = 0;
                }
                if (position > lti.getItemCount() - lti.getPageSize())
                { // position > count of entries is not possible, set to max
                    position = lti.getItemCount() - lti.getPageSize();
                }
                if (position > 0)
                { // we are not at position 0, "skipping" entries
                    r.skipRows(position);
                }
                else
                    position = 0;
                // maxItems
                maxItems = lti.getPageSize();
            }


            // Read all Items
            items = r.getBeanList(beanClass, maxItems);
            if (items == null)
                throw new UnexpectedReturnValueException(items, "DBReader.getBeanList");
            generateIdParams(rowset, items);
            assignSelectionMap(items);


            // set position at session object
            if (loadPageFromPosition)
            { // set valid
                if (position + items.size() > lti.getItemCount())
                { // Oops: More items than expected.
                    log.warn("Item count of {} has changed. Adjusting item count.", getPropertyName());
                    lti.init(position + items.size(), lti.getPageSize());
                }
                lti.setPosition(position);
                lti.setModified(false);
                lti.setValid(true);
            }
            else
            { // Init the list
                lti.init(items.size(), 0);
            }
        }
        catch (RuntimeException e)
        {
            log.error("Error loading bean list " + e.getMessage(), e);
            throw e;
        }
        finally
        {
            r.close();
            // Pagination
            if (lti.isAllowPagination())
            { // Scrollbar   
                if (initScrollbar)
                    initScrollbar();

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