Develop Reference

Why don't work on the device and work on the simulator?

I'm making an app that access a mysql DB. I'm using direct JDBC, not web service. The simulator access with no problem but the real device give the error
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
This is the code of the connection class (its only the connection method)
public static Connection CONN(String name) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder()
.permitAll().build();
StrictMode.setThreadPolicy(policy);
Connection conn = null;
String ConnURL = null;
try {
Class.forName(classs);
conn = DriverManager.getConnection(url, un, password);
String stsql = "Select version()";
Toaster.toast(name);
//conn = DriverManager.getConnection(ConnURL);
} catch (SQLException se) {
Log.e("ERRO", se.getMessage());
Toaster.toast(se.getMessage());
System.out.println( se.getMessage() );
} catch (ClassNotFoundException e) {
Log.e("ERRO", e.getMessage());
} catch (Exception e) {
Log.e("ERRO", e.getMessage());
}
return conn;
}
Can someone gives me some help?
Thanks!

DB connection pooling in Neo4j jdbc driver

In my application I'm using neo4j-community-2.3.0-M02 with neo4j-jdbc 2.3.2 . It creates large number of threads each should execute 3 or 4 cypher queries. To execute queries I use following method,
private ResultSet executeCypher(String queryString) throws Exception {
try {
String restUrl = getPropertiesCache().getCofigProperty("neo4j_url");
String driver = getPropertiesCache().getCofigProperty("neo4j_driver");
String userName = getPropertiesCache().getCofigProperty("neo4j_user");
String passWord = getPropertiesCache().getCofigProperty("neo4j_pwd");
Class.forName(driver);
try{
Neo4jConnection connection = (Neo4jConnection)
DriverManager.getConnection(restUrl, userName, passWord);
try {
PreparedStatement stmt = connection.prepareStatement(queryString);
try{
ResultSet rs = (ResultSet) stmt.executeQuery(queryString);
stmt.close();
connection.close();
return rs;
}catch (SQLException e){
e.printStackTrace();
} catch (NullPointerException e1){
e1.printStackTrace();
} catch (RuntimeException e2){
e2.printStackTrace();
}
if(!stmt.isClosed()){
stmt.close();
}
}catch (Exception e){
e.printStackTrace();
}
if(!connection.isClosed()){
connection.close();
}
}catch (Exception e){
e.printStackTrace();
}
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
Which means I'm creating db connection for each cypher query. I think it's very bad idea because when creating large number of connections most of them start to be timeout. I think db connection pooling will help on this case or is there any better idea regarding this than connection pool?
If connection pooling solve this issue, please give an example of how to create db connection pool using neo4j jdbc driver.

The neo4j-jdbc 2.3X driver uses the REST API to connect to the database, basically they are http calls using Restlet API, so there is no connection being opened or closed when you create/close JDBC connections.

Unable to reopen MySQL connection in Java

I've got an annoying bug in Java. I'm connecting to a MySQL database and using Tomcat in Eclipse. It works brilliantly, but only the first time around. If I reload the page or run the page again, I get a com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after connection closed.
This is my code:
Connection conn = null;
String returnString = null;
Response response = null;
ResultSet rs = null;
try {
System.out.println("Trying to connect");
conn = DbUtil.getConnection(); // Connect to the database
System.out.println("Okay, connected");
query = conn.prepareStatement("SELECT host_firstname FROM host"); //Crashes at this line!
rs = query.executeQuery();
ConvertToJson jsonConverter = new ConvertToJson();
JSONArray jsonArray = new JSONArray();
jsonArray = jsonConverter.convertToJsonArray(rs);
returnString = jsonArray.toString();
response = Response.ok(returnString).build();
}
catch (Exception e) {
e.printStackTrace();
System.out.println("hello!!!!");
}
finally {
if (rs != null){
rs.close();
}
if (query != null) {
query.close();
}
if (conn != null) {
conn.close();
}
}
return response;
I've seen everywhere I've Googled that I have to close the result set, the prepared statement and the connection (in that order) but once I've closed the connection, I can't reopen it.
This is my DbUtil class:
private static Connection connection = null;
public static Connection getConnection() {
if (connection != null) {
return connection;
}
else {
try {
Properties prop = new Properties();
InputStream inputStream = DbUtil.class.getClassLoader().getResourceAsStream("/db.properties");
prop.load(inputStream);
String driver = prop.getProperty("driver");
String url = prop.getProperty("url");
String user = prop.getProperty("user");
String password = prop.getProperty("password");
Class.forName(driver);
connection = DriverManager.getConnection(url, user, password);
}
catch (IOException e) {
e.printStackTrace();
}
catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return connection;
}
Any idea what is causing this problem?
Thanks
Omar :)

This answer is just to get your code working. But the best way would be to configure a connection pool. You should look about it.
YOur condition is :
if (connection != null) {
return connection; It's returning a closed connection
}
Try changing it to:
if (connection != null && !connection.isClosed()) {
return connection;
}

About JDBC Connection

A very simple question but i'm newbie in Java. How can I do the connection with my SQL Server DataBase that are in my network ?
I made the download of the JDBC 4.0, associate the file in my project and I'm trying the follow code, but I don't know how can I do a reference to my database
try {
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
String connectionUrl = "what i put here ?";
Connection con = DriverManager.getConnection(connectionUrl, "sa", "testtest");
} catch (SQLException e) {
e.printStackTrace();
}
catch (ClassNotFoundException e) {
e.printStackTrace();
}

String url = "jdbc:mysql://localhost:3306/";
String db = "yourDB";
String driver = "com.mysql.jdbc.Driver";
String user = "root";
String pass = "";
try {
Class.forName(driver);
Connection con = DriverManager.getConnection(url + db, user, pass);
con.setAutoCommit(true);
} catch (ClassNotFoundException e1) {
e1.printStackTrace();
} catch (SQLException e1) {
e1.printStackTrace();
}

try {
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
DriverManager.getConnection("jdbc:sqlserver://url.com;database=dbname;user=username;password=test")
} catch (SQLException e) {
e.printStackTrace();
}
catch (ClassNotFoundException e) {
e.printStackTrace();
}
replace the url/username/password. This is the connectionstring for sql server

Connecting To a URL through java in Blackberry

I am trying to connect to a URL through a Java program in Blackberry simulator. But it is not connecting.
try {
HttpConnection httpConn;
StreamConnection s;
s = (StreamConnection)Connector.open("http://www.google.com/");
httpConn = (HttpConnection)s;
status = httpConn.getResponseCode();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
int t=0;
if (status == HttpConnection.HTTP_OK)
{
add(new RichTextField("Successfully Authorized", Field.NON_FOCUSABLE));
}

s = (StreamConnection)Connector.open("http://www.google.com"+";deviceside=true");
try with this line...
If you are trying in emulator means use deviceside=true
If its in a mobile means for wifi connection you have to use interface=wifi