GWT e mysql

package org.page.client;

import com.google.gwt.user.client.rpc.RemoteService;

import com.google.gwt.user.client.rpc.RemoteServiceRelativePath;

public interface GWTService extends RemoteService{

public String getBoolean(boolean bo);

}

package org.page.client;

import com.google.gwt.user.client.rpc.AsyncCallback;

import com.google.gwt.user.client.rpc.RemoteService;

public interface GWTServiceAsync extends RemoteService{

public abstract void getBoolean(boolean bo, AsyncCallback callback);

}

public String getBoolean(Boolean bo) {
         //aqui sera executada as funçoes do lado server
         //como acesso a arquivos, busca de dados em bd, etc
     return bo; // aki sera retornado o valor neste exemplo eh boolean mas pode ser qualquer um outro
}

public void onFailure(Throwable caught) {

		//se ouver algum erro
                  RootPanel.get().add(new HTML(caught.toString());

}

public void onSuccess(boolean result) {

//se 	tudo der certo

RootPanel.get().add(new HTML(“O valor retornado é” + result);

}

});

com.google.gwt.user.client.rpc.StatusCodeException: 
HTTP Status 404 - /Portal/org.yournamehere.Main/GWTServiceImpl

--------------------------------------------------------------------------------

type Status report

message /Portal/org.yournamehere.Main/GWTServiceImpl

description The requested resource (/Portal/org.yournamehere.Main/GWTServiceImpl) is not available.


--------------------------------------------------------------------------------

Apache Tomcat/6.0.18

JDBC Connector

    * Add a JDBC connector jar to your Build Path
    * I put it here. My Projects are configured like: /opt/gwt-linux/mysql-connector-java-5.0.8-bin.jar
    * Check your Eclipse referenced libraries for jar
    * Example Eclipse Project Source code of Mysql Conn - http://gwt-examples.googlecode.com/svn/trunk/gwt-test-MySQLConn/src/com/tribling/gwt/test/mysqlconn/server/ 

    Links

    * JDBC Connector - http://www.mysql.com/products/connector/j/ - download MySQL Connector/J 5.1
    * Example MySQL Database, The King James Bible Download Bible Database Here (It comes as a MySQL Dump) 

Tomcat Setup

    When you use tomcat, the servlet container has to be given access outside of its container. More info here: gwtTomcat. 

    * Fix this problem: java.security.AccessControlException access denied (java.net.SocketPermission localhost resolve)
    * More information on this here: gwtTomcat 

    You will need to change Tomcat configuration.

    #for debian/ubuntu
    # I added to /etc/tomcat5.5/policy.d/04webapps.policy
    # Or make your own /etc/tomcat5.5/policy.d/myGWTPolicys.policy
    # you can also change file to: file:/apps/directory/yourGWTTomcatApps/- 
    grant codeBase "file:${catalina.home}/webapps/-" {
          permission java.net.SocketPermission "192.168.12.81:3306", "connect";
    };

Code Snippets

    MySQL Connection
    Connect to db. Don't forget to change the parameters.

    /**
     * db conn
     * 
     * Make sure you add a reference library (external jar in build path) JDBC Connector - 
     * You will see I put it in /opt/gwt-linux/mysql-connector-java-5.0.8-bin.jar
     * 
     * @return Connection
     */
    private Connection getConn() {

                Connection conn     = null;
                String url          = "jdbc:mysql://192.168.12.81:3306/";
                String db           = "hostdb";
                String driver       = "com.mysql.jdbc.Driver";
                String user         = "";
                String pass         = "";
                    
            try {
                    Class.forName(driver).newInstance();
            } catch (InstantiationException e) {
                    e.printStackTrace();
            } catch (IllegalAccessException e) {
                    e.printStackTrace();
            } catch (ClassNotFoundException e) {
                    e.printStackTrace();
            }
            try {
                            
                            conn = DriverManager.getConnection(url+db, user, pass);
            } catch (SQLException e) {
                            System.err.println("Mysql Connection Error: ");
                    e.printStackTrace();
            }
                    return conn;
    }

    Get Row Count
    Use this to size an array for your values

    /*
     * get row count
     */
    protected static int getResultSetSize(ResultSet resultSet) {
        int size = -1;

        try {
            resultSet.last();
            size = resultSet.getRow();
            resultSet.beforeFirst();
        } catch(SQLException e) {
            return size;
        }

        return size;
    }

    Query
    Query statement, using connection, statement, resultset, and get record. Setup a connection first.

    String query = "SELECT * FROM table";
     
    try {
        Connection conn = this.getConn();
        Statement select = conn.createStatement();
        ResultSet result = select.executeQuery(query);
        while (result.next()) {
            String s = result.getString(1);
        }
        select.close();
        result.close();
        conn.close();
    } catch(SQLException e) {
            System.err.println("Mysql Statement Error: " + query);
            e.printStackTrace();
    }

    Update / Insert
    Update and Insert into database, MySql or MsSql or whatever database you have. Setup a connection first

    //save session data to table 
    String query = "INSERT INTO `session` (UserID, SessionID, LastAccessed, DateCreated) " +
                               "VALUES ('" + this.dbUserID + "', '" + this.SessionID + "' , UNIX_TIMESTAMP(), UNIX_TIMESTAMP());";

    try {
        Connection conn = this.getConn();
        Statement update = conn.createStatement();
        update.executeUpdate(query);
        
        //get last id 
        ResultSet result = update.getGeneratedKeys(); 
        if (result != null && result.next()) { 
            int rsId = result.getInt(1);  
        }

        result.close();
        update.close();
        conn.close();
    } catch(SQLException e) {
        System.err.println("Mysql Statement Error: " + query);
        e.printStackTrace();
    }

    Escape String For SQL
    Apache has some cool functions for escaping strings. This can only be run on server side, preparing the sql data for insert. You don't have to unescape b/c it comes out as is. It just allows you to save with "'" '"' in the string. 

    * Right Click Project > Build Path > Configure Build Path > Libraries > Add External Jar
    * Link to Apache jar documentation: Classes Documentation
    * Download Jar: Goto Download

      import org.apache.commons.lang.StringEscapeUtils;

      /**
       * escape string to db
       * @param s
       * @return
       */
      protected static String escapeForSql(String s) {

              String rtn = StringEscapeUtils.escapeSql(s);
              
              return rtn;
      }

    Improved Escape method for fixing data before its stuck into db

    /**
     * escape string to db
     * 
     * remove harmfull db content
     * remove harmfull tags
     *
     * @param s
     * @return
     */
    protected static String escapeForSql(String s) {
            
            //remove harmful HTML tags
            if (s != null) {
                    s = s.replaceAll("(?i)</?(HTML|SCRIPT|HEAD|CSS)\\b[^>]*>", ""); 
            }

            String rtn = StringEscapeUtils.escapeSql(s);
            
            //escape utils returns null if null
            if (rtn == null) {
                    rtn = "";
            }

            return rtn;
    }

Trasporting Data / Recordsets Around

    This is an example of how I transport data from server to client and back. This is my favorite way and by far the most efficient and easiest way to do it. 

    I use a class like this to store MySQL record set data into an object array. This makes it very easy to pass around data. Now if you use private methods and/or fields in the class that goes from server to client, you will have have to change Tomcat security. See more in gwtTomcat.

    /**
     * I use this class to store my mysql recordset in an object that is an array.
     * This will give an example of how I pass data from the server to client in an object, 
     * one of my favorites for its simplicity.
     * 
     * @author branflake2267
     *
     */
    public class BibleData implements IsSerializable {

            // fields to store data
            public String book;
            public int howManyChapters;
            public int howManyVerses;
            
            /**
             * constructor
             */
            public BibleData() {
                    // nothing to do when transporting
            }
            
    }

    This is an example of how I spool the data into the Object Array from MySQL.

    public BibleData[] getBibleInfo() {
            
            String query = "SELECT bid, en FROM book;";
            
            // prepare for rpc transport
            BibleData[] bibleData = null;
            
        try {
            Connection connection = getConn();
            Statement select = connection.createStatement();
            ResultSet result = select.executeQuery(query);
           
            // init object into the size we need, like a recordset
            int rsSize = getResultSetSize(result); //size the array
            bibleData = new BibleData[rsSize];
            
            int i = 0;
            while (result.next()) {
                    
                    // init each object in the array !!!!
                    bibleData[i] = new BibleData(); // <-THIS IS CRITICAL TO REMEMBER!!!! init each array with the object type (I forget to do this so often)
                    
                    int bid = result.getInt(1);
                    bibleData[i].book = result.getString(2);
                    bibleData[i].howManyChapters = getHowManyChapters(bid);
                    bibleData[i].howManyVerses = getHowManyVerses(bid);
                    
                i++;
            }
            
            // clean up
            result.close();
            connection.close();
            
        } catch(Exception e) {
            
            System.err.println("Mysql Statement Error: " + query);
            e.printStackTrace();
            
        }
            
        // return the array
        return bibleData;
    }

Feed Back Widget

The feedback widget in the repository gathers up the inputs and sends them to the server and inserts them into MySql.

    * Feedback widget Demo
    * SVN FeedBack Widget Project - Eclipse project for my Feedback widget 

    My Feedback Table

    CREATE TABLE `gv_feedback` (
      `ID` int(11) NOT NULL auto_increment,
      `UserID` int(11) default NULL,
      `FromEmail` varchar(150) default NULL,
      `FromName` varchar(150) default NULL,
      `Subject` varchar(250) default NULL,
      `Message` text,
      `Suggestion` tinyint(1) default '0',
      `Comment` tinyint(1) default '0',
      `Problem` tinyint(1) default '0',
      `Other` tinyint(1) default '0',
      `Post` tinyint(1) default NULL,
      `DateCreated` int(11) NOT NULL default '0',
      `LastUpdated` int(11) default NULL,
      PRIMARY KEY  (`ID`),
      KEY `UserID` (`UserID`)
    ) ENGINE=MyISAM DEFAULT CHARSET=latin1