[`Class.forName()`][1] is not directly related to JDBC at all. It simply loads a class.

Most JDBC Driver classes register themselves in their static initializers by calling [`registerDriver()`][2].

`registerDriver()` is the real call that you hardly ever need to call yourself (unless you write your own JDBC driver).

Note that in JDBC 4 you should not need *either of those* if your JDBC driver is up-to-date, as drivers can be found using the service location mechanisms instead (i.e. simply leave out that call and open your connection as usual). See the [documentaton of `DriverManager`][3] for details:

&gt; The DriverManager methods `getConnection` and `getDrivers` have been enhanced to support the Java Standard Edition Service Provider mechanism. JDBC 4.0 Drivers must include the file `META-INF/services/java.sql.Driver`. This file contains the name of the JDBC drivers implementation of `java.sql.Driver`. For example, to load the `my.sql.Driver` class, the `META-INF/services/java.sql.Driver` file would contain the entry:
&gt;
&gt;     my.sql.Driver
&gt; 
&gt; Applications no longer need to explictly load JDBC drivers using `Class.forName()`. Existing programs which currently load JDBC drivers using `Class.forName()` will continue to work without modification.

  [1]: http://download.oracle.com/javase/6/docs/api/java/lang/Class.html#forName%28java.lang.String%29
  [2]: http://download.oracle.com/javase/6/docs/api/java/sql/DriverManager.html#registerDriver%28java.sql.Driver%29
  [3]: http://download.oracle.com/javase/6/docs/api/java/sql/DriverManager.html

Never call `DriverManager.registerDriver()` method manually. The JDBC spec requires a driver to register itself when the class is loaded, and the class is loaded via `Class.forName()`. In JDBC 4 the drivers are able to be loaded automatically just by being on the class path.

`DriverManager.registerDriver()` manually is potentially dangerous since it actually causes the Driver to be registered twice. If your code requires you to deregister a Driver to prevent a memory leak then you would only end up deregistering it once and leave a second instance registered. 

In additaion to what Joachim Sauer already mentioned about JDBC 4 drivers, note that in practice you usually want to **inject** either an EntityManager (JPA) or a pooled DataSource (and use JdbcTemplate of Spring).

I need to get previous month and year, relative to current date.

However, see following example.

    // Today is 2011-03-30
    echo date(&#39;Y-m-d&#39;, strtotime(&#39;last month&#39;));

    // Output:
    2011-03-02

This behavior is understandable (to a certain point), due to different number of days in february and march, and code in example above is what I need, but works only 100% correctly for between 1st and 28th of each month.

So, how to get last month AND year (think of `date(&quot;Y-m&quot;)`) in the most elegant manner as possible, which works for every day of the year? Optimal solution will be based on `strtotime` argument parsing.

Update. To clarify requirements a bit.

I have a piece of code that gets some statistics of last couple of months, but I first show stats from last month, and then load other months when needed. That&#39;s intended purpose. So, during THIS month, I want to find out which month-year should I pull in order to load PREVIOUS month stats.

I also have a code that is timezone-aware (not really important right now), and that accepts `strtotime`-compatible string as input (to initialize internal date), and then allows date/time to be adjusted, also using `strtotime`-compatible strings.

I know it can be done with few conditionals and basic math, but that&#39;s really messy, compared to this, for example (if it worked correctly, of course):

    echo tz::date(&#39;last month&#39;)-&gt;format(&#39;Y-d&#39;)

So, I ONLY need previous month and year, in a `strtotime`-compatible fashion.


Answer (thanks, @dnagirl):

    // Today is 2011-03-30
    echo date(&#39;Y-m-d&#39;, strtotime(&#39;first day of last month&#39;)); // Output: 2011-02-01

How to get previous month and year relative to today, using strtotime and date?

I&#39;m using Eclipse. Say I have a project &#39;ProjectA&#39; in the eclipseworkspace (in a folder ProjectA). I want to copy the project but with a new name (ProjectB) and have all the references in the new project adjusted. I can&#39;t find much help for what I thought would be a vary basic operation. I want to try out variations on the original design/code and creating a copy seemed the obvious way to go about it.

Any suggestions please.

Android - copy existing project with a new name in Eclipse

Which is the difference from `forName` method vs `registerDriver` to load and register a JDBC driver?

JDBC Class.forName vs DriverManager.registerDriver

<p>Which is the difference from <code>forName</code> method vs <code>registerDriver</code> to load and register a JDBC driver?</p>


I have the following code 

    public Object handlePermission(ProceedingJoinPoint joinPoint, RequirePermission permission) throws AccessException, Throwable {
        System.out.println(&quot;Permission = &quot; + permission.value());
        if (user.hasPermission(permission.value())) {
            System.out.println(&quot;Permission granted &quot;);
            return joinPoint.proceed();
        } else {
            System.out.println(&quot;No Permission&quot;);
            throw new AccessException(&quot;Current user does not have required permission&quot;);
        }

    }

When I use a user that does not have permissions, I get `java.lang.reflect.UndeclaredThrowableException` instead of `AccessException`. 

Getting UndeclaredThrowableException instead of my own exception

I would like to parse data from JSON which is of type `String`.
I am using [Google Gson][1].

I have:

    jsonLine = &quot;
    {
     &quot;data&quot;: {
      &quot;translations&quot;: [
       {
        &quot;translatedText&quot;: &quot;Hello world&quot;
       }
      ]
     }
    }
    &quot;;

and my class is:

    public class JsonParsing{
    
       public void parse(String jsonLine) {
        
          // there I would like to get String &quot;Hello world&quot;
      
       }
    
    }


  [1]: http://code.google.com/p/google-gson/

JSON parsing using Gson for Java

How do I persuade Windows to use the JDK instead of a JRE?

This question has been asked before, here and elsewhere:

https://stackoverflow.com/questions/551668/how-do-i-set-the-default-java-installation-runtime-windows

The trouble is that Windows ignores `JAVA_HOME` and it also ignores the fact that I made the JDK bin directory the first entry in the path.

When I run `java -version` from the command line, instead of invoking my JDK 1.6 installation, it runs the 1.7 JRE.

My guess is that this is a problem specific to 1.7, and Windows 7 is doing something it shouldn&#39;t with the registry.

Any ideas on how to fix this?

**Edit**: Oops. I wrote &quot;first entry in the classpath&quot; above, when I meant &quot;path&quot;. Sorry.


Windows ignores JAVA_HOME: how to set JDK as default?

A very simple &amp; quick question on Java libraries: is there a ready-made class that implements a `Queue` with a fixed maximum size - i.e. it always allows addition of elements, but it will silently remove head elements to accomodate space for newly added elements.

Of course, it&#39;s trivial to implement it manually:

    import java.util.LinkedList;

    public class LimitedQueue&lt;E&gt; extends LinkedList&lt;E&gt; {
        private int limit;
    
        public LimitedQueue(int limit) {
            this.limit = limit;
        }
    
        @Override
        public boolean add(E o) {
            super.add(o);
            while (size() &gt; limit) { super.remove(); }
            return true;
        }
    }

As far as I see, there&#39;s no standard implementation in Java stdlibs, but may be there&#39;s one in Apache Commons or something like that?

Size-limited queue that holds last N elements in Java

I have found `AtomicInteger`, `AtomicLong`, but where is `AtomicFloat` (or `AtomicDouble`)? Maybe there is some trick?

Java: is there no AtomicFloat or AtomicDouble?

I am trying to create a connection to my database, when I put test my code using the main method, it works seamlessly. However, when trying to access it through Tomcat 7, it fails with error: 

&lt;!-- language: lang-none --&gt;

    No suitable driver found for jdbc:mysql://localhost/dbname. 

I am using pooling. I put in mysql connector (5.1.15), dbcp (1.4) , and pool(1.4.5) libraries in WEB-INF/lib and in .classpath as well. I am using Eclipse IDE. My code for the database driver is:

&lt;!-- language: lang-java --&gt;

    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.SQLException;

    import org.apache.tomcat.dbcp.dbcp.ConnectionFactory;
    import org.apache.tomcat.dbcp.dbcp.DriverManagerConnectionFactory;
    import org.apache.tomcat.dbcp.dbcp.PoolableConnectionFactory;
    import org.apache.tomcat.dbcp.dbcp.PoolingDriver;
    import org.apache.tomcat.dbcp.pool.impl.GenericObjectPool;

    public class DatabaseConnector {
        public static String DB_URI = &quot;jdbc:mysql://localhost/dbname&quot;;
        public static String DB_USER = &quot;test&quot;;
        public static String DB_PASS = &quot;password&quot;;

        // Singleton instance
        protected static DatabaseConnector _instance;

        protected String _uri;
        protected String _username;
        protected String _password;

        /**
         * Singleton, so no public constructor
         */
        protected DatabaseConnector(String uri, String username, String password) {
            _uri = uri;
            _username = username;
            _password = password;

            GenericObjectPool connectionPool = new GenericObjectPool(null);
            ConnectionFactory connectionFactory = new DriverManagerConnectionFactory(
                _uri, _username, _password);
            PoolableConnectionFactory poolableConnectionFactory =
                new PoolableConnectionFactory(connectionFactory, connectionPool,
                                                null, null, false, true);
            PoolingDriver driver = new PoolingDriver();
            driver.registerPool(&quot;test&quot;, connectionPool);
        }

        /**
         * Returns the singleton instance
         */
        public static DatabaseConnector getInstance() {
            if (_instance == null) {
                _instance = new DatabaseConnector(DB_URI, DB_USER, DB_PASS);
            }
            return _instance;
        }

        /**
         * Returns a connection to the database
         */
        public Connection getConnection() {
            Connection con = null;
            try {
                con = DriverManager.getConnection(&quot;jdbc:apache:commons:dbcp:test&quot;);
            } catch (SQLException e) {
                throw new RuntimeException(e);
            }
            return con;
        }
    }

Start of my stack trace:

&lt;!-- language: lang-none --&gt;

    Apr 5, 2011 9:49:14 PM org.apache.catalina.core.StandardWrapperValve invoke
    SEVERE: Servlet.service() for servlet [Login] in context with path [/Project] 
    threw exception
    java.lang.RuntimeException: java.sql.SQLException: 
    No suitable driver found for jdbc:mysql://localhost/dbname

What is causing this error?

How to fix: &quot;No suitable driver found for jdbc:mysql://localhost/dbname&quot; error when using pools?

I&#39;m getting this exception when I try to run this program. It&#39;s one of the Microsoft examples. I&#39;ve added the sqljdbc4.jar to the classpath in netbeans for both compile and Run, via the project properties. I also tested that the class could be found by using an import statement below - no error during compile, so it must be finding the jar.

Could it be related to a dll or some sql dll that the sqldbc4.jar references?

This is the exact exception, and below is the exact code, except for password.

Exception:

    run:
    java.sql.SQLException: No suitable driver found for jdbc:microsoft:sqlserver://localhost:1433;databaseName=HealthCareDatabase
    Error Trace in getConnection() : No suitable driver found for jdbc:microsoft:sqlserver://localhost:1433;databaseName=HealthCareDatabase
    Error: No active Connection
    	at java.sql.DriverManager.getConnection(DriverManager.java:602)
    	at java.sql.DriverManager.getConnection(DriverManager.java:185)
    	at javaapplication1.Connect.getConnection(Connect.java:35)
    	at javaapplication1.Connect.displayDbProperties(Connect.java:50)
    	at javaapplication1.JavaApplication1.main(JavaApplication1.java:23)
    BUILD SUCCESSFUL (total time: 1 second)


Code:

     package javaapplication1;
    import com.microsoft.sqlserver.jdbc.SQLServerDriver;
    
    import java.*;
    
    public class Connect {
    
        private java.sql.Connection con = null;
        private final String url = &quot;jdbc:microsoft:sqlserver://&quot;;
        private final String serverName = &quot;localhost&quot;;
        private final String portNumber = &quot;1433&quot;;
        private final String databaseName = &quot;HealthCareDatabase&quot;;
        private final String userName = &quot;larry&quot;;
        private final String password = &quot;xxxxxxx&quot;;
      
        // Constructor
        public Connect() {
        }
    
        private String getConnectionUrl() {
            return url + serverName + &quot;:&quot; + portNumber + &quot;;databaseName=&quot; + databaseName ;
        }
    
        private java.sql.Connection getConnection() {
            try {
                Class.forName(&quot;com.microsoft.sqlserver.jdbc.SQLServerDriver&quot;);
                con = java.sql.DriverManager.getConnection(getConnectionUrl(), userName, password);
                if (con != null) {
                    System.out.println(&quot;Connection Successful!&quot;);
                }
            } catch (Exception e) {
                e.printStackTrace();
                System.out.println(&quot;Error Trace in getConnection() : &quot; + e.getMessage());
            }
            return con;
        }
    
        public void displayDbProperties() {
            java.sql.DatabaseMetaData dm = null;
            java.sql.ResultSet rs = null;
            try {
                con = this.getConnection();
                if (con != null) {
                    dm = con.getMetaData();
                    System.out.println(&quot;Driver Information&quot;);
                    System.out.println(&quot;\tDriver Name: &quot; + dm.getDriverName());
                    System.out.println(&quot;\tDriver Version: &quot; + dm.getDriverVersion());
                    System.out.println(&quot;\nDatabase Information &quot;);
                    System.out.println(&quot;\tDatabase Name: &quot; + dm.getDatabaseProductName());
                    System.out.println(&quot;\tDatabase Version: &quot; + dm.getDatabaseProductVersion());
                    System.out.println(&quot;Avalilable Catalogs &quot;);
                    rs = dm.getCatalogs();
                    while (rs.next()) {
                        System.out.println(&quot;\tcatalog: &quot; + rs.getString(1));
                    }
                    rs.close();
                    rs = null;
                    closeConnection();
                } else {
                    System.out.println(&quot;Error: No active Connection&quot;);
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
            dm = null;
        }
    
        private void closeConnection() {
            try {
                if (con != null) {
                    con.close();
                }
                con = null;
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    
        public static void main(String[] args) throws Exception {
            Connect myDbTest = new Connect();
            myDbTest.displayDbProperties();
        }

}




java.sql.SQLException: No suitable driver found for jdbc:microsoft:sqlserver

Which JDBC connection pool library should I use for a new application project (not web application)?

 - Apache DBCP has [enough unresolved issues][1] which are pushed until 2.0 I think. 
 - [C3P0][2] development seems to be stopped. 
 - And both of them [looks relatively slow][3].
 - [Proxool][4] is dead.
 - [DBPool][5] has almost no community (at least I&#39;ve found no public one - no forums, no mailing lists...)
 - [Apache Tomcat Pool][6] looks to be unusable without Tomcat
 - I&#39;ve found [SQL Datasources][7] article at Oracle website, but it seems, that it can be applied only to applets running in containers like servlets and web services.

Should I choose [BoneCP][8] may be? I don&#39;t have any huge requirements. I just need a good and easy to use database connection pool, that is in active development. Library, whose author can respond to bug reports, answer some specific question etc.

BTW, actually, I&#39;m using MySQL only. I&#39;ve found, that MySQL driver [supports DriverManager][9] interface, but I&#39;m unsure if it actually pools connections or not.


  [1]: https://issues.apache.org/jira/secure/IssueNavigator.jspa?reset=true&amp;pid=12310469&amp;sorter/field=issuekey&amp;sorter/order=DESC&amp;status=1&amp;status=4
  [2]: http://sourceforge.net/projects/c3p0
  [3]: http://jolbox.com/
  [4]: http://proxool.sourceforge.net/
  [5]: http://www.snaq.net/java/DBPool/
  [6]: http://people.apache.org/~fhanik/jdbc-pool/jdbc-pool.html
  [7]: http://download.oracle.com/javase/tutorial/jdbc/basics/sqldatasources.html
  [8]: http://jolbox.com/
  [9]: http://dev.mysql.com/doc/refman/5.5/en/connector-j-usagenotes-basic.html#connector-j-examples-connection-drivermanager

Java JDBC connection pool library choice in 2011/2012?

I&#39;m trying to connect to Oracle 10.2.0 from NetBeans, using the following connection string:

    jdbc:oracle:thin:@localhost:1521:XE

The weirdest part is that everything worked fine, until the one of the reboots. I started getting this TNS-12505 errors all the time; look at the final entries in my `listener.log`:

    TNSLSNR for 32-bit Windows: Version 10.2.0.1.0 - Production on 14-APR-2011 13:46:48
    
    Copyright (c) 1991, 2005, Oracle.  All rights reserved.
    
    System parameter file is D:\oraclexe\app\oracle\product\10.2.0\server\network\admin\listener.ora
    Log messages written to D:\oraclexe\app\oracle\product\10.2.0\server\network\log\listener.log
    Trace information written to D:\oraclexe\app\oracle\product\10.2.0\server\network\trace\listener.trc
    Trace level is currently 0
    
    Started with pid=3460
    Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(PIPENAME=\\.\pipe\EXTPROC_FOR_XEipc)))
    Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=Brodyaga-PC)(PORT=1521)))
    Listener completed notification to CRS on start
    
    TIMESTAMP * CONNECT DATA [* PROTOCOL INFO] * EVENT [* SID] * RETURN CODE
    14-APR-2011 13:48:54 * (CONNECT_DATA=(SID=XE)(CID=(PROGRAM=JDBC Thin Client)(HOST=__jdbc__)(USER=Brodyaga))) * (ADDRESS=(PROTOCOL=tcp)(HOST=127.0.0.1)(PORT=58458)) * establish * XE * 12505
    TNS-12505: TNS:listener does not currently know of SID given in connect descriptor
    14-APR-2011 13:49:00 * (CONNECT_DATA=(SID=XE)(CID=(PROGRAM=JDBC Thin Client)(HOST=__jdbc__)(USER=Brodyaga))) * (ADDRESS=(PROTOCOL=tcp)(HOST=127.0.0.1)(PORT=58481)) * establish * XE * 12505
    TNS-12505: TNS:listener does not currently know of SID given in connect descriptor
    14-APR-2011 13:49:02 * (CONNECT_DATA=(SID=XE)(CID=(PROGRAM=JDBC Thin Client)(HOST=__jdbc__)(USER=Brodyaga))) * (ADDRESS=(PROTOCOL=tcp)(HOST=127.0.0.1)(PORT=58487)) * establish * XE * 12505
    TNS-12505: TNS:listener does not currently know of SID given in connect descriptor
    14-APR-2011 13:50:23 * (CONNECT_DATA=(CID=(PROGRAM=)(HOST=)(USER=Brodyaga))(COMMAND=services)(ARGUMENTS=64)(SERVICE=LISTENER)(VERSION=169869568)) * services * 0

The first three entries are my attempts to connect from NetBeans.  The fourth, the connection via SQL*Plus, worked just fine.

Here are the contents of my **`listener.ora`**:

    SID_LIST_LISTENER =
      (SID_LIST =
        (SID_DESC =
          (SID_NAME = PLSExtProc)
          (ORACLE_HOME = D:\oraclexe\app\oracle\product\10.2.0\server)
          (PROGRAM = extproc)
        )
        (SID_DESC =
          (SID_NAME = CLRExtProc)
          (ORACLE_HOME = D:\oraclexe\app\oracle\product\10.2.0\server)
          (PROGRAM = extproc)
        )
      )
    
    LISTENER =
      (DESCRIPTION_LIST =
        (DESCRIPTION =
          (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC_FOR_XE))
          (ADDRESS = (PROTOCOL = TCP)(HOST = Brodyaga-PC)(PORT = 1521))
        )
      )
    
    DEFAULT_SERVICE_LISTENER = (XE)

And **`tnsnames.ora`**:

    XE =
      (DESCRIPTION =
        (ADDRESS = (PROTOCOL = TCP)(HOST = Brodyaga-PC)(PORT = 1521))
        (CONNECT_DATA =
          (SERVER = DEDICATED)
          (SERVICE_NAME = XE)
        )
      )
    
    EXTPROC_CONNECTION_DATA =
      (DESCRIPTION =
        (ADDRESS_LIST =
          (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC_FOR_XE))
        )
        (CONNECT_DATA =
          (SID = PLSExtProc)
          (PRESENTATION = RO)
        )
      )
    
    ORACLR_CONNECTION_DATA = 
      (DESCRIPTION = 
        (ADDRESS_LIST = 
          (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC_FOR_XE)) 
        ) 
        (CONNECT_DATA = 
          (SID = CLRExtProc) 
          (PRESENTATION = RO) 
        ) 
      ) 

And output from &gt; **lsnrctl services**

    C:\Users\Brodyaga&gt;lsnrctl services
    
    LSNRCTL for 32-bit Windows: Version 10.2.0.1.0 - Production on 14-APR-2011 13:59
    :45
    
    Copyright (c) 1991, 2005, Oracle.  All rights reserved.
    
    Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC_FOR_XE)))
    Services Summary...
    Service &quot;CLRExtProc&quot; has 1 instance(s).
      Instance &quot;CLRExtProc&quot;, status UNKNOWN, has 1 handler(s) for this service...
        Handler(s):
          &quot;DEDICATED&quot; established:0 refused:0
             LOCAL SERVER
    Service &quot;PLSExtProc&quot; has 1 instance(s).
      Instance &quot;PLSExtProc&quot;, status UNKNOWN, has 1 handler(s) for this service...
        Handler(s):
          &quot;DEDICATED&quot; established:0 refused:0
             LOCAL SERVER
    The command completed successfully

Both Oracle services are started and SQL*Plus connects fine. 

Is there some workaround for this error?

TNS-12505: TNS:listener does not currently know of SID given in connect descriptor

For given [`Connection`][1] instance how do I find out url that the `Connection` uses to connect the database ? Is it somewhere in `Properties` returned by [`Connection.getClientInfo()`][2] method?

If there you need me to provide clearer description all comments are welcome. Thank you


  [1]: http://download.oracle.com/javase/1.4.2/docs/api/java/sql/Connection.html
  [2]: http://download.oracle.com/javase/6/docs/api/java/sql/Connection.html#getClientInfo%28%29

Content Type	Original Author	Original Content on Stackoverflow
Question	xdevel2000	View Question on Stackoverflow
Solution 1 - Java	Joachim Sauer	View Answer on Stackoverflow
Solution 2 - Java	David O'Meara	View Answer on Stackoverflow
Solution 3 - Java	Puce	View Answer on Stackoverflow

JDBC Class.forName vs DriverManager.registerDriver

Java Problem Overview

Java Solutions

Solution 1 - Java

Solution 2 - Java

Solution 3 - Java

Android - copy existing project with a new name in Eclipse

How to get previous month and year relative to today, using strtotime and date?

Attributions