Current Topic: 4.4.4.6.2. DataService handling DB connections
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DataService handling DB connections
The framework does most of the plumbing work of connecting to DB and executing the SQL statements.
To better understand how this is done, take a look at the extracts from several sources.
DataService framework can be used in a stand alone desktop application as well as in a web application.
In the extracts we focus on the case of web applications where main configuration variables are provided in the web.xml - file.
For a big application with many action-services there is a need for action-specific configuration messages.
Such data are provided in specific configuration files, which are handled by the ConversationManager class considered in another lesson.
When a web application starts, DataService framework automatically initiates both: messages and data pool by providing these two lines in the ItsBaseServlet.contextInitialized() method:
ConversationManager.init(appName); // init messages
DataService.init(appName); // init DB connections
Sample Here are the extracts from the DataService class that reads the DB configuration variables and creates a connection pool.
public class DataService {
public static String defaultMySqlPort = "3306";
public static String defaultDbType = "mysql";
public static String oracleDriverName = "oracle.jdbc.driver.OracleDriver";
public static String mySqlDriverName = "com.mysql.jdbc.Driver";
public static String msSqlDriverName = "com.microsoft.sqlserver.jdbc.SQLServerDriver";
public static String postgreSqlDriverName = "org.postgresql.Driver";
public static String defaultMySqlConURL = "jdbc:mysql://localhost:3306/content?user=root&password=lowtide"; // mySql
public static String defaultOracleXeConURL = "jdbc:oracle:thin:admin/pswdt@localhost:1521:xe";
public static String defaultPostgreConURL = "jdbc:postgresql://localhost:5432/lportal?user=postgres&password=postgres"; // postgtres
public static String dynamicMySqlConURL = "jdbc:mysql://{hostname}:{dbPort}/{dbName}?user={userName}&password={password}"; // mySql
public static String dynamicMsSqlConURL = "jdbc:microsoft:sqlserver://{hostname}:{dbPort};User={userName};Password={password};DatabaseName={dbName}"; // MS SQL conURL - must replace {parameters}
public static String dynamicPostgreConURL = "jdbc:postgresql://{hostname}:{dbPort}/{dbName}?user={userName}&password={password}"; // postgtres
public static String dynamicOracleConURL = "jdbc:oracle:thin:{userName}/{password}@{hostname}:{dbPort}:{dbName}";
public static String defaultSqlLocation = "config/sql";
public static String oraclePoolDataSourceClassName = "oracle.jdbc.pool.OracleDataSource";
public static String mySqlPoolDataSourceClassName = "com.mysql.jdbc.jdbc2.optional.MysqlDataSource";
private static String[] dbConnectComponents = {
"microsoft",msSqlDriverName, dynamicMsSqlConURL, "SQLServer2008Dialect", //A dialect for Microsoft SQL Server 2008 with JDBC Driver 3.0 and above
"postgresql", postgreSqlDriverName, dynamicPostgreConURL, "PostgreSQLDialect",
"mysql", mySqlDriverName, dynamicMySqlConURL, "MySQLDialect", // An SQL dialect for MySQL (prior to 5.x) or MySQL5Dialect for 5.0 features
"oracle", oracleDriverName, dynamicOracleConURL, "OracleDialect"};
public static List listOfDbConnectComponents = Arrays.asList(dbConnectComponents);
public static Hashtable dataSources = new Hashtable();
/**
* initDs() is called usually at a start time; for web apps by contextInitialized() - automatic call by a system
* In the DataService framework it is called by the ItsBaseServlet.contextInitialized()
* @param appName
*/
public static void initDs(String appName) {
// dbParamString in web.xml: dbName, userName, psw, dsName, sqlLocation, hostname, dbPort, dbType-->
String dbParamString = Stats.getAppDetailsByKeyName(appName, "dbParamString");
String[] dbParams = Stringer.split(",", dbParamString);
String dbName = dbParams[0].trim();
String userName = dbParams[1].trim();
String psw = dbParams[2].trim();
String originDsName = dbParams[3].trim(); // for example, "sampleDB"
String dsName = appName +"/" + originDsName; // for example, "BASE/sampleDB"
String pathToDeploy = Stats.getAppDetailsByKeyName(appName, "pathToDeploy");
String appLocationName = Stats.getAppDetailsByKeyName(appName, "appLocationName");
String sqlLocation = pathToDeploy + appLocationName + "/" + DataService.defaultSqlLocation; // config/sql
if(dbParams.length > 4) {
sqlLocation = pathToDeploy + appLocationName + "/" + dbParams[4].trim();
}
String hostname = "localhost"; // default hostname
if(dbParams.length > 5) {
hostname = dbParams[5].trim();
}
String dbPort = DataService.defaultMySqlPort; // default port for mysql
if(dbParams.length > 6) {
dbPort = dbParams[6].trim();
}
String dbType = DataService.defaultDbType; // "mysql"
String dbDriverName = DataService.mySqlDriverName;
String dbURL = DataService.defaultMySqlConURL;
if(dbParams.length > 7) {
// use dbType to get dbURL and dbDriver
dbType = dbParams[7].trim().toLowerCase(); // microsoft,postgresql,mysql,oracle (db2?)
int indexOfDbType = DataService.listOfDbConnectComponents.indexOf(dbType);
if(indexOfDbType >= 0) {
dbDriverName = DataService.listOfDbConnectComponents.get(indexOfDbType + 1);
dbURL = DataService.listOfDbConnectComponents.get(indexOfDbType + 2);
}
}
createConnectionPool(dbURL, dbName, userName, psw, dbDriverName, dsName);
// source is not provided, consists of simple IOMaster.readTextFile() in the loop
readAndStoreSql(appName, sqlLocation); // read SQL files and cache in the Hashtable
}
/**
* Getting a connection from a pool of connections
* @param dsName
* @return connection
* @throws Exception
*/
public static Connection getConnection(String dsName) throws Exception {
// retrieve a proper data source
DataSource ds = dataSources.get(dsName);
// dataSources - a Hashtable with dsName as a key and DataSource object populated in the createConnectionPool()
// get a connection from the pool
return ds.getConnection();
}
/**
* createConnectionPool() uses db params from web.xml
* @param dbURL
* @param dbName
* @param username
* @param password
* @param driverName
* @param dsName
* @return dbURL
*/
public static String createConnectionPool(String dbURL, String dbName, String username, String password,
String driverName, String dsName) {
if(driverName.equals(msSqlDriverName)) {
/** Uncomment to work with MS SQL Server (0), Postgresql (1), or MySql (2) DB ....
* if this application needs more DB types, provide proper jars in the library and add similar code
com.microsoft.sqlserver.jdbc.SQLServerConnectionPoolDataSource msds = new com.microsoft.sqlserver.jdbc.SQLServerConnectionPoolDataSource();
msds.setURL(connectionUrl);
msds.setUser(username);
msds.setPassword(password);
setDataSource(dsName, msds);
return;
] else if(driverName.equals(postgreSqlDriverName)) {
org.postgresql.ds.PGSimpleDataSource pds = new org.postgresql.ds.PGSimpleDataSource();
pds.setDatabaseName(dbName);
pds.setServerName(hostname);
pds.setPortNumber(Integer.parseInt(dbPort));
pds.setUser(username);
pds.setPassword(password);
setDataSource(dsName, pds);
return;
//optional for mysql, remove if mysql.jar is not in the lib
*/
} else if(driverName.equals(mySqlDriverName)) {
MysqlDataSource pds = new MysqlDataSource();
pds.setURL(dbURL);
pds.setUser(username);
pds.setPassword(password);
dataSources.put(dsName, pds);
return dbURL;
} else if(driverName.equals(oracleDriverName)) {
try {
OracleDataSource opds = new OracleDataSource();
opds.setURL(dbURL);
opds.setUser(username);
opds.setPassword(password);
dataSources.put(dsName, opds);
} catch(Exception e) {
System.out.println("ERROR: "+e.getMessage());
}
}
return dbURL;
}
}
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<br/>ConversationManager.init(appName); // init messages
<br/>DataService.init(appName); // init DB connections
<br/>
Sample Here are the extracts from the DataService class that reads the DB configuration variables and creates a connection pool.
<br/>public class DataService {
<br/> public static String defaultMySqlPort = "3306";
<br/> public static String defaultDbType = "mysql";
<br/> public static String oracleDriverName = "oracle.jdbc.driver.OracleDriver";
<br/> public static String mySqlDriverName = "com.mysql.jdbc.Driver";
<br/> public static String msSqlDriverName = "com.microsoft.sqlserver.jdbc.SQLServerDriver";
<br/> public static String postgreSqlDriverName = "org.postgresql.Driver";
<br/>
<br/> public static String defaultMySqlConURL = "jdbc:mysql://localhost:3306/content?user=root&password=lowtide"; // mySql
<br/> public static String defaultOracleXeConURL = "jdbc:oracle:thin:admin/pswdt@localhost:1521:xe";
<br/> public static String defaultPostgreConURL = "jdbc:postgresql://localhost:5432/lportal?user=postgres&password=postgres"; // postgtres
<br/>
<br/> public static String dynamicMySqlConURL = "jdbc:mysql://{hostname}:{dbPort}/{dbName}?user={userName}&password={password}"; // mySql
<br/> public static String dynamicMsSqlConURL = "jdbc:microsoft:sqlserver://{hostname}:{dbPort};User={userName};Password={password};DatabaseName={dbName}"; // MS SQL conURL - must replace {parameters}
<br/> public static String dynamicPostgreConURL = "jdbc:postgresql://{hostname}:{dbPort}/{dbName}?user={userName}&password={password}"; // postgtres
<br/> public static String dynamicOracleConURL = "jdbc:oracle:thin:{userName}/{password}@{hostname}:{dbPort}:{dbName}";
<br/>
<br/> public static String defaultSqlLocation = "config/sql";
<br/> public static String oraclePoolDataSourceClassName = "oracle.jdbc.pool.OracleDataSource";
<br/> public static String mySqlPoolDataSourceClassName = "com.mysql.jdbc.jdbc2.optional.MysqlDataSource";
<br/>
<br/> private static String[] dbConnectComponents = {
<br/> "microsoft",msSqlDriverName, dynamicMsSqlConURL, "SQLServer2008Dialect", //A dialect for Microsoft SQL Server 2008 with JDBC Driver 3.0 and above
<br/> "postgresql", postgreSqlDriverName, dynamicPostgreConURL, "PostgreSQLDialect",
<br/> "mysql", mySqlDriverName, dynamicMySqlConURL, "MySQLDialect", // An SQL dialect for MySQL (prior to 5.x) or MySQL5Dialect for 5.0 features
<br/> "oracle", oracleDriverName, dynamicOracleConURL, "OracleDialect"};
<br/> public static List<String> listOfDbConnectComponents = Arrays.asList(dbConnectComponents);
<br/>
<br/> public static Hashtable<String, DataSource> dataSources = new Hashtable<String, DataSource>();
<br/> /**
<br/> * initDs() is called usually at a start time; for web apps by contextInitialized() - automatic call by a system
<br/> * In the DataService framework it is called by the ItsBaseServlet.contextInitialized()
<br/> * @param appName
<br/> */
<br/> public static void initDs(String appName) {
<br/> // dbParamString in web.xml: dbName, userName, psw, dsName, sqlLocation, hostname, dbPort, dbType-->
<br/> String dbParamString = Stats.getAppDetailsByKeyName(appName, "dbParamString");
<br/> String[] dbParams = Stringer.split(",", dbParamString);
<br/> String dbName = dbParams[0].trim();
<br/> String userName = dbParams[1].trim();
<br/> String psw = dbParams[2].trim();
<br/> String originDsName = dbParams[3].trim(); // for example, "sampleDB"
<br/> String dsName = appName +"/" + originDsName; // for example, "BASE/sampleDB"
<br/> String pathToDeploy = Stats.getAppDetailsByKeyName(appName, "pathToDeploy");
<br/> String appLocationName = Stats.getAppDetailsByKeyName(appName, "appLocationName");
<br/> String sqlLocation = pathToDeploy + appLocationName + "/" + DataService.defaultSqlLocation; // config/sql
<br/> if(dbParams.length > 4) {
<br/> sqlLocation = pathToDeploy + appLocationName + "/" + dbParams[4].trim();
<br/> }
<br/> String hostname = "localhost"; // default hostname
<br/> if(dbParams.length > 5) {
<br/> hostname = dbParams[5].trim();
<br/> }
<br/> String dbPort = DataService.defaultMySqlPort; // default port for mysql
<br/> if(dbParams.length > 6) {
<br/> dbPort = dbParams[6].trim();
<br/> }
<br/> String dbType = DataService.defaultDbType; // "mysql"
<br/> String dbDriverName = DataService.mySqlDriverName;
<br/> String dbURL = DataService.defaultMySqlConURL;
<br/> if(dbParams.length > 7) {
<br/> // use dbType to get dbURL and dbDriver
<br/> dbType = dbParams[7].trim().toLowerCase(); // microsoft,postgresql,mysql,oracle (db2?)
<br/> int indexOfDbType = DataService.listOfDbConnectComponents.indexOf(dbType);
<br/> if(indexOfDbType >= 0) {
<br/> dbDriverName = DataService.listOfDbConnectComponents.get(indexOfDbType + 1);
<br/> dbURL = DataService.listOfDbConnectComponents.get(indexOfDbType + 2);
<br/> }
<br/> }
<br/> createConnectionPool(dbURL, dbName, userName, psw, dbDriverName, dsName);
<br/> // source is not provided, consists of simple IOMaster.readTextFile() in the loop
<br/> readAndStoreSql(appName, sqlLocation); // read SQL files and cache in the Hashtable
<br/> }
<br/>
<br/> /**
<br/> * Getting a connection from a pool of connections
<br/> * @param dsName
<br/> * @return connection
<br/> * @throws Exception
<br/> */
<br/> public static Connection getConnection(String dsName) throws Exception {
<br/> // retrieve a proper data source
<br/> DataSource ds = dataSources.get(dsName);
<br/> // dataSources - a Hashtable with dsName as a key and DataSource object populated in the createConnectionPool()
<br/> // get a connection from the pool
<br/> return ds.getConnection();
<br/> }
<br/> /**
<br/> * createConnectionPool() uses db params from web.xml
<br/> * @param dbURL
<br/> * @param dbName
<br/> * @param username
<br/> * @param password
<br/> * @param driverName
<br/> * @param dsName
<br/> * @return dbURL
<br/> */
<br/> public static String createConnectionPool(String dbURL, String dbName, String username, String password,
<br/> String driverName, String dsName) {
<br/> if(driverName.equals(msSqlDriverName)) {
<br/> /** Uncomment to work with MS SQL Server (0), Postgresql (1), or MySql (2) DB ....
<br/> * if this application needs more DB types, provide proper jars in the library and add similar code
<br/>
<br/> com.microsoft.sqlserver.jdbc.SQLServerConnectionPoolDataSource msds = new com.microsoft.sqlserver.jdbc.SQLServerConnectionPoolDataSource();
<br/>
<br/> msds.setURL(connectionUrl);
<br/> msds.setUser(username);
<br/> msds.setPassword(password);
<br/> setDataSource(dsName, msds);
<br/> return;
<br/> ] else if(driverName.equals(postgreSqlDriverName)) {
<br/> org.postgresql.ds.PGSimpleDataSource pds = new org.postgresql.ds.PGSimpleDataSource();
<br/> pds.setDatabaseName(dbName);
<br/> pds.setServerName(hostname);
<br/> pds.setPortNumber(Integer.parseInt(dbPort));
<br/> pds.setUser(username);
<br/> pds.setPassword(password);
<br/> setDataSource(dsName, pds);
<br/> return;
<br/> //optional for mysql, remove if mysql.jar is not in the lib
<br/> */
<br/> } else if(driverName.equals(mySqlDriverName)) {
<br/> MysqlDataSource pds = new MysqlDataSource();
<br/> pds.setURL(dbURL);
<br/> pds.setUser(username);
<br/> pds.setPassword(password);
<br/> dataSources.put(dsName, pds);
<br/> return dbURL;
<br/> } else if(driverName.equals(oracleDriverName)) {
<br/> try {
<br/> OracleDataSource opds = new OracleDataSource();
<br/> opds.setURL(dbURL);
<br/> opds.setUser(username);
<br/> opds.setPassword(password);
<br/> dataSources.put(dsName, opds);
<br/> } catch(Exception e) {
<br/> System.out.println("ERROR: "+e.getMessage());
<br/> }
<br/> }
<br/> return dbURL;
<br/> }
<br/>}
<br/>
Was it clear so far? Highlight the text in question
Or onclick="window.location.href='/BASE/jsp/chat.jsp?issueID=474&ur=f'">
Assignments: 1. Read the source and expand the description of each method in the Discussion section
2. Add suggestions and questions to the source there.
3. Provide 2 QnA related to this lesson.
We invite you to create your own questions and answers (QnA) to increase your rank and win the Top Creativity Prize!
