Develop Reference

Getting all columns from get result in HBase dynamically

I am working on a Get object as retrieved from a table in Habse. I want to dynamically retrieve all column values related to that get since I don't know the exact name of column families
val result1 = hTable.get(g)
if (!result1.isEmpty) {
//binaryEpisodes = result1.getValue(Bytes.toBytes("episodes"),Bytes.toBytes("episodes"))
//instead of above retrieve all values dynamically
}

Simple way :
get rawcells and knowing CF , columns information.
You have to do something like below example
public static void printResult(Result result, Logger logger) {
logger.info("Row: ");
for (Cell cell : result.rawCells()) {
byte[] family = CellUtil.cloneFamily(cell);
byte[] column = CellUtil.cloneQualifier(cell);
byte[] value = CellUtil.cloneValue(cell);
logger.info("\t" + Bytes.toString(family) + ":" + Bytes.toString(column) + " = " + Bytes.toString(value));
}
}
Hbase Admin way : Hbase client API was exposed by HbaseAdmin class like below...
Client would be like
package mytest;
import com.usertest.*;
import java.io.IOException;
import java.util.Date;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
public class ListHbaseTablesAndColumns {
public static void main(String[] args) {
try {
HbaseMetaData hbaseMetaData =new HbaseMetaData();
for(String hbaseTable:hbaseMetaData .getTableNames(".*yourtables.*")){
for (String column : hbaseMetaData .getColumns(hbaseTable, 10000)) {
System.out.println(hbaseTable + "," + column);
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
Use below class to Get HbaseMetaData..
package com.usertest;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.*;
import org.apache.hadoop.hbase.client.*;
import org.apache.hadoop.hbase.filter.PageFilter;
import java.io.IOException;
import java.util.*;
import java.util.regex.Pattern;
public class HbaseMetaData {
private HBaseAdmin hBaseAdmin;
private Configuration hBaseConfiguration;
public HbaseMetaData () throws IOException {
this.hBaseConfiguration = HBaseConfiguration.create();
this.hBaseAdmin = new HBaseAdmin(hBaseConfiguration);
}
/** get all Table names **/
public List<String> getTableNames(String regex) throws IOException {
Pattern pattern=Pattern.compile(regex);
List<String> tableList = new ArrayList<String>();
TableName[] tableNames=hBaseAdmin.listTableNames();
for (TableName tableName:tableNames){
if(pattern.matcher(tableName.toString()).find()){
tableList.add(tableName.toString());
}
}
return tableList;
}
/** Get all columns **/
public Set<String> getColumns(String hbaseTable) throws IOException {
return getColumns(hbaseTable, 10000);
}
/** get all columns from the table **/
public Set<String> getColumns(String hbaseTable, int limitScan) throws IOException {
Set<String> columnList = new TreeSet<String>();
HTable hTable=new HTable(hBaseConfiguration, hbaseTable);
Scan scan=new Scan();
scan.setFilter(new PageFilter(limitScan));
ResultScanner results = hTable.getScanner(scan);
for(Result result:results){
for(KeyValue keyValue:result.list()){
columnList.add(
new String(keyValue.getFamily()) + ":" +
new String(keyValue.getQualifier())
);
}
}
return columnList;
}
}

Java program to insert value in Aerospike database not working

I have written a java program to insert an integer and a double in aerospike database. Here is the code snippet
import com.aerospike.client.AerospikeClient;
import com.aerospike.client.Bin;
import com.aerospike.client.Key;
import com.aerospike.client.policy.WritePolicy;
public class Test{
public static void main(String[] args){
try{
AerospikeClient client = new AerospikeClient("192.168.140.62", 3000);
for(int i=0;i<10000;i++){
try {
WritePolicy writePolicy = new WritePolicy();
Key key = new Key("test" , "myset", "mykey");
double randomDouble = Math.random();
Bin bin1 = new Bin("ID",i);
Bin bin2 = new Bin("Value",randomDouble);
client.put(writePolicy,key,bin1,bin2);
} catch (Exception e) {
e.printStackTrace();
}
}
client.close();
}
catch(Exception e){
e.printStackTrace();
}
}
}
The problem is the above code snippet is neither inserting any data nor throwing any errors. Please advise.
PS: I am new to aerospike

read from csv file in java

I have a huge CSV file.I have to read it and store in a database using java.below code only read about 2000 rows from that file and store it into database.why? note the below calculation is to change the seconds to minutes with approximation.dont think a lot about that
import com.opencsv.CSVReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
public class ReadCSV {
public static void main(String[] args) throws SQLException{
MainController mc = new MainController();
boolean status=false;
String csvFile = "C:/Users/Thanushiya/Desktop/mobios/internship/csvfile/csvfile/Master.csv";
CSVReader reader = null;
List myList = new ArrayList();
String[] row = null;
int duration_m = 0;
try {
reader = new CSVReader (new FileReader(csvFile), ',', '\'', 17);
myList = reader.readAll();
int i=0;
for (Object object : myList) {
row = (String[]) object;
float duration_float = Float.parseFloat(row[12]) / 60 ;
float duration_mod = duration_float % 1 ;
if(Integer.parseInt(row[12]) <= 60){
duration_m = 1;
}
else{
if(duration_mod == 0 ){
duration_m = (int) duration_float;
}
else{
duration_m = ((int) duration_float) + 1;
}
}
String query = "INSERT INTO master(msisdn,serv,start,end,ringwithdurartion,duration_s,status,cid,duration_m) values ('"+row[0]+"','"+row[4]+"','"+row[8]+"','"+row[10]+"','"+row[11]+"','"+row[12]+"','"+row[13]+"','"+row[15]+"','"+duration_m+"')";
status=mc.insertData(query);
}//end for
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (reader != null) {
try {
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
System.out.println("Done");
}
}

With readAll() you're loading (or at least trying to load) the entire file into memory at once. That will severely limit the number of lines you can read before running out of memory. As indicated on the OpenCSV homepage, there's also an iterator that reads line per line:
CSVReader reader = new CSVReader(new FileReader("C:/Users/Thanushiya/Desktop/mobios/internship/csvfile/csvfile/Master.csv"), ',', '\'', 17);
String [] nextLine;
while ((nextLine = reader.readNext()) != null) {
// put the code from your for loop here
}

Database connection suffers of concurrent threads

I've recently starting working on a java webapp (JSP / Servlet) that was developed by the internal developer of a company.
This app randomly doesn't return data, and inspecting the log I found some NullPointerExceptions related to the classes' member variable which holds the database connection. Following the stack trace it seems that a second thread closes the connection after it ended its task leaving the first thread without a connection.
By the needs of the company the app uses different databases, one which rules appdata, and others which contain data the app has to retrieve. So every class attached to the main servlet may connect to one or more databases depending on the task it has to accomplish.
I'm not familiar with JavaEE but giving a look at the database connection class, I see nothing which protect threads from conflicting each other.
Which is the correct way to handle such connections?
This is the code of the Database handler:
package it.metmi.mmasgis.utils;
import java.sql.*;
import java.util.ArrayList;
import java.util.HashMap;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
public class DBManager
{
private String szDatabase;
private String szUsername;
private String szPassword;
private String szError;
private Connection db;
private boolean bConnected;
private Logger logger;
public DBManager(String szDBName)
{
this(szDBName, "", "");
}
public DBManager(String szDBName, String szName, String szPass)
{
szDatabase = szDBName;
szUsername = szName;
szPassword = szPass;
bConnected = false;
szError = "";
logger = LogManager.getFormatterLogger(DBManager.class.getName());
}
public boolean connect()
{
logger.entry();
try {
Class.forName("com.mysql.jdbc.Driver");
if(!szDatabase.isEmpty())
{
String szCon = "jdbc:mysql://localhost/" + szDatabase;
if(!szUsername.isEmpty())
{
szCon += "?user=" + szUsername;
if(!szPassword.isEmpty())
szCon += "&password=" + szPassword;
}
db = DriverManager.getConnection(szCon);
bConnected = true;
} else {
logger.error("No database name!!");
System.exit(0);
}
} catch(SQLException | ClassNotFoundException e) {
szError = e.getMessage();
e.printStackTrace();
logger.error("Can't connect: %s", e);
}
return logger.exit(bConnected);
}
public void disconnect()
{
logger.entry();
try {
db.close();
bConnected = false;
} catch(SQLException e) {
e.printStackTrace();
logger.error("Can't disconnect: %s", e);
}
logger.exit();
}
public boolean isConnected()
{
return bConnected;
}
public String getError()
{
return szError;
}
public ArrayList<HashMap<String,String>> query(String szQuery)
{
logger.entry(szQuery);
ArrayList<HashMap<String,String>> aResults = new ArrayList<HashMap<String,String>>();
int iCols = 0;
try {
Statement stmt = db.createStatement();
logger.info("Query: %s", szQuery);
ResultSet rs = stmt.executeQuery(szQuery);
ResultSetMetaData rsmd = rs.getMetaData();
iCols = rsmd.getColumnCount();
while(rs.next())
{
HashMap<String,String> pv = new HashMap<String,String>();
for(int i = 0; i < iCols; i++)
{
String szCol = rsmd.getColumnLabel(i + 1);
String szVal = rs.getString(i + 1);
pv.put(szCol, szVal);
}
aResults.add(pv);
}
rs.close();
stmt.close();
} catch(SQLException e) {
e.printStackTrace();
szError = e.getMessage();
logger.error("Error executing query: %s", e);
}
return logger.exit(aResults);
}
public boolean update(String szQuery)
{
logger.entry(szQuery);
boolean bResult = false;
try {
Statement stmt = db.createStatement();
logger.info("Query: %s", szQuery);
stmt.executeUpdate(szQuery);
bResult = true;
stmt.close();
} catch(SQLException e) {
e.printStackTrace();
szError = e.getMessage();
bResult = false;
logger.error("Error executing query: %s", e);
}
return logger.exit(bResult);
}
}
The class Task which all the servlet classes are based on, is a simple abstract class:
package it.metmi.mmasgis.servlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public abstract class Task
{
public abstract void doTask(HttpServletRequest request, HttpServletResponse response);
}
The class which throws NullPointerExceptions it this one, during the invocation of db.disconnect(). This class is called rapidly via AJAX 4 or 5 times from the interface written in JS.
package it.metmi.mmasgis.servlet.params;
import it.metmi.mmasgis.servlet.Task;
import it.metmi.mmasgis.utils.Const;
import it.metmi.mmasgis.utils.DBManager;
import it.metmi.mmasgis.utils.Query;
import it.metmi.mmasgis.utils.Utility;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.HashMap;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
public class ClassType extends Task
{
private DBManager db = null;
private Logger logger = LogManager.getFormatterLogger(ClassType.class.getName());
#Override
public void doTask(HttpServletRequest request, HttpServletResponse response)
{
logger.entry(request, response);
String szCensimento = Utility.getParameter(request, "censimento");
String szCategoria = Utility.getParameter(request, "category");
ArrayList<HashMap<String,String>> aClasses = new ArrayList<HashMap<String,String>>();
PrintWriter out = null;
logger.debug("Census: %s", szCensimento);
logger.debug("Category: %s", szCategoria);
db = new DBManager(szCensimento, Const.DB_USER, Const.DB_PASS);
if(db.connect())
{
String szQuery = String.format(Query.classes, szCategoria, szCategoria);
aClasses = db.query(szQuery);
db.disconnect();
}
try {
out = response.getWriter();
jsonEncode(aClasses, out);
} catch(IOException e) {
e.printStackTrace();
logger.error("Failed to encode JSON: %s", e);
}
logger.exit();
}
private void jsonEncode(ArrayList<HashMap<String,String>> aData, PrintWriter out)
{
HashMap<String,Object> result = new HashMap<String,Object>();
result.put("results", aData);
result.put("success", true);
Gson gson = new GsonBuilder().create();
gson.toJson(result, out);
}
}
If the webapp would use only one database, it could be rewritten as a Singleton, but in this way I have no idea on how to handle different connections for different databases.
How can avoid these exceptions?

The problem was that the connection object was declared as member.
Moving the variable inside the methods resolved.

Inserting records into Berkeley DB with Java

I can't seem to find sample code for constructing a Berkeley DB in Java and inserting records into it. Any samples? And I do not mean the Berkeley DB Java Edition either.

http://www.oracle.com/technology/documentation/berkeley-db/db/programmer_reference/BDB_Prog_Reference.pdf
Chapter 5
If you download db-5.0.21.NC.zip you will see plenty of samples.
Here is one that seems to do what you want
/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 2004, 2010 Oracle and/or its affiliates. All rights reserved.
*
* $Id$
*/
// File: ExampleDatabaseLoad.java
package db.GettingStarted;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import java.util.StringTokenizer;
import java.util.Vector;
import com.sleepycat.bind.EntryBinding;
import com.sleepycat.bind.serial.SerialBinding;
import com.sleepycat.bind.tuple.TupleBinding;
import com.sleepycat.db.DatabaseEntry;
import com.sleepycat.db.DatabaseException;
public class ExampleDatabaseLoad {
private static String myDbsPath = "./";
private static File inventoryFile = new File("./inventory.txt");
private static File vendorsFile = new File("./vendors.txt");
// DatabaseEntries used for loading records
private static DatabaseEntry theKey = new DatabaseEntry();
private static DatabaseEntry theData = new DatabaseEntry();
// Encapsulates the databases.
private static MyDbs myDbs = new MyDbs();
private static void usage() {
System.out.println("ExampleDatabaseLoad [-h <database home>]");
System.out.println(" [-i <inventory file>] [-v <vendors file>]");
System.exit(-1);
}
public static void main(String args[]) {
ExampleDatabaseLoad edl = new ExampleDatabaseLoad();
try {
edl.run(args);
} catch (DatabaseException dbe) {
System.err.println("ExampleDatabaseLoad: " + dbe.toString());
dbe.printStackTrace();
} catch (Exception e) {
System.out.println("Exception: " + e.toString());
e.printStackTrace();
} finally {
myDbs.close();
}
System.out.println("All done.");
}
private void run(String args[])
throws DatabaseException {
// Parse the arguments list
parseArgs(args);
myDbs.setup(myDbsPath);
System.out.println("loading vendors db....");
loadVendorsDb();
System.out.println("loading inventory db....");
loadInventoryDb();
}
private void loadVendorsDb()
throws DatabaseException {
// loadFile opens a flat-text file that contains our data
// and loads it into a list for us to work with. The integer
// parameter represents the number of fields expected in the
// file.
List vendors = loadFile(vendorsFile, 8);
// Now load the data into the database. The vendor's name is the
// key, and the data is a Vendor class object.
// Need a serial binding for the data
EntryBinding dataBinding =
new SerialBinding(myDbs.getClassCatalog(), Vendor.class);
for (int i = 0; i < vendors.size(); i++) {
String[] sArray = (String[])vendors.get(i);
Vendor theVendor = new Vendor();
theVendor.setVendorName(sArray[0]);
theVendor.setAddress(sArray[1]);
theVendor.setCity(sArray[2]);
theVendor.setState(sArray[3]);
theVendor.setZipcode(sArray[4]);
theVendor.setBusinessPhoneNumber(sArray[5]);
theVendor.setRepName(sArray[6]);
theVendor.setRepPhoneNumber(sArray[7]);
// The key is the vendor's name.
// ASSUMES THE VENDOR'S NAME IS UNIQUE!
String vendorName = theVendor.getVendorName();
try {
theKey = new DatabaseEntry(vendorName.getBytes("UTF-8"));
} catch (IOException willNeverOccur) {}
// Convert the Vendor object to a DatabaseEntry object
// using our SerialBinding
dataBinding.objectToEntry(theVendor, theData);
// Put it in the database.
myDbs.getVendorDB().put(null, theKey, theData);
}
}
private void loadInventoryDb()
throws DatabaseException {
// loadFile opens a flat-text file that contains our data
// and loads it into a list for us to work with. The integer
// parameter represents the number of fields expected in the
// file.
List inventoryArray = loadFile(inventoryFile, 6);
// Now load the data into the database. The item's sku is the
// key, and the data is an Inventory class object.
// Need a tuple binding for the Inventory class.
TupleBinding inventoryBinding = new InventoryBinding();
for (int i = 0; i < inventoryArray.size(); i++) {
String[] sArray = (String[])inventoryArray.get(i);
String sku = sArray[1];
try {
theKey = new DatabaseEntry(sku.getBytes("UTF-8"));
} catch (IOException willNeverOccur) {}
Inventory theInventory = new Inventory();
theInventory.setItemName(sArray[0]);
theInventory.setSku(sArray[1]);
theInventory.setVendorPrice((new Float(sArray[2])).floatValue());
theInventory.setVendorInventory((new Integer(sArray[3])).intValue());
theInventory.setCategory(sArray[4]);
theInventory.setVendor(sArray[5]);
// Place the Vendor object on the DatabaseEntry object using our
// the tuple binding we implemented in InventoryBinding.java
inventoryBinding.objectToEntry(theInventory, theData);
// Put it in the database. Note that this causes our secondary database
// to be automatically updated for us.
myDbs.getInventoryDB().put(null, theKey, theData);
}
}
private static void parseArgs(String args[]) {
for(int i = 0; i < args.length; ++i) {
if (args[i].startsWith("-")) {
switch(args[i].charAt(1)) {
case 'h':
myDbsPath = new String(args[++i]);
break;
case 'i':
inventoryFile = new File(args[++i]);
break;
case 'v':
vendorsFile = new File(args[++i]);
break;
default:
usage();
}
}
}
}
private List loadFile(File theFile, int numFields) {
List records = new ArrayList();
try {
String theLine = null;
FileInputStream fis = new FileInputStream(theFile);
BufferedReader br = new BufferedReader(new InputStreamReader(fis));
while((theLine=br.readLine()) != null) {
String[] theLineArray = splitString(theLine, "#");
if (theLineArray.length != numFields) {
System.out.println("Malformed line found in " + theFile.getPath());
System.out.println("Line was: '" + theLine);
System.out.println("length found was: " + theLineArray.length);
System.exit(-1);
}
records.add(theLineArray);
}
fis.close();
} catch (FileNotFoundException e) {
System.err.println(theFile.getPath() + " does not exist.");
e.printStackTrace();
usage();
} catch (IOException e) {
System.err.println("IO Exception: " + e.toString());
e.printStackTrace();
System.exit(-1);
}
return records;
}
private static String[] splitString(String s, String delimiter) {
Vector resultVector = new Vector();
StringTokenizer tokenizer = new StringTokenizer(s, delimiter);
while (tokenizer.hasMoreTokens())
resultVector.add(tokenizer.nextToken());
String[] resultArray = new String[resultVector.size()];
resultVector.copyInto(resultArray);
return resultArray;
}
protected ExampleDatabaseLoad() {}
}

There are a number of good Getting Started Guides for Oracle Berkeley DB Java Edition. They are included in the documentation set. You'll find example code in the documentation. If you're new to Oracle Berkeley DB Java Edition that's the right place to start. There are other examples in the download package as well.
I'm the product manager for Oracle Berkeley DB, I hope this addressed your question. If not please let me know how else I can help you.