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DbPool
Represents a pool of connections to a particular database configuration.
To connect to a database, you first create a pool of database connections and then access individual connections as needed. For more information on the general methodology for using DbPool objects, see Writing Server-Side JavaScript Applications.
创建源
The DbPool constructor.
描述
The lifetime of a DbPool object (its scope) varies. Assuming it has been assigned to a variable, a DbPool object can go out of scope at different times:
It is your responsibility to release all connections and close all cursors, stored procedures, and result sets associated with a DbPool object before that object goes out of scope. Release connections and close the other objects as soon as you are done with them.
If you do not release a connection, it remains bound and is unavailable to the next user until the associated DbPool object goes out of scope. When you do call release to give up a connection, the runtime engine waits until all associated cursors, stored procedures, and result sets are closed before actually releasing the connection. Therefore, you must close those objects when you are done with them.
You can use the prototype property of the DbPool object to add a property to all DbPool instances. If you do so, that addition applies to all DbPool objects running in all applications on your server, not just in the single application that made the change. This allows you to expand the capabilities of this object for your entire server.
属性概览
方法概览
属性
prototype
Represents the prototype for this class. You can use the prototype to add properties or methods to all instances of a class. For information on prototypes, see Function.prototype.
方法
DbPool
Creates a pool of database Connection objects and optionally connects the objects to a particular configuration of database and user.
语法
new DbPool();
new DbPool (dbtype, serverName, username, password, databaseName);
new DbPool (dbtype, serverName, username, password, databaseName, maxConnections);
new DbPool (dbtype, serverName, username, password, databaseName, maxConnections, commitflag);
参数
描述
The first version of this constructor takes no parameters. It instantiates and allocates memory for a DbPool object. This version of the constructor creates and caches one connection. When this connection goes out of scope, pending transactions are rolled back.
The second version of this constructor instantiates a DbPool object and then calls the connect method to establish a database connection. This version of the constructor also creates and caches one connection. When this connection goes out of scope, pending transactions are rolled back.
The third version of this constructor instantiates a DbPool object and then calls the connect method to establish a database connection. In addition, it attempts to create as many connections as specified by the maxConnections parameter. If successful, it stores those connections for later use. If the runtime engine does not obtain the requested connections, it returns an error. When this connection goes out of scope, pending transactions are rolled back.
The fourth version of this constructor does everything the third version does. In addition, the commitflag parameter indicates what to do with pending transactions when the connection goes out of scope. If this parameter is false (the default), a pending transaction is rolled back. If this parameter is true, a pending transaction if committed.
To detect errors, you can use the majorErrorCode method.
If possible, your application should call this constructor and make the database connection on its initial page. Doing so prevents conflicts from multiple client requests trying to manipulate the status of the connections at once.
connect
Connects the pool to a particular configuration of database and user.
语法
connect (dbtype, serverName, username, password, databaseName)
connect (dbtype, serverName, username, password, databaseName, maxConnections)
connect (dbtype, serverName, username, password, databaseName, maxConnections, commitflag)
参数
返回
0 if the call was successful; otherwise, a nonzero status code based on any error message passed by the database. If the method returns a nonzero status code, use the associated majorErrorCode and majorErrorMessage methods to interpret the cause of the error.
描述
When you call this method, the runtime engine first closes and releases any currently open connections. It then reconnects the pool with the new configuration. You should be sure that all connections have been released before calling this method.
The first version of this method creates and caches one connection. When this connection goes out of scope, pending transactions are rolled back.
The second version of this method attempts to create as many connections as specified by the maxConnections parameter. If successful, it stores those connections for later use. If the runtime engine does not obtain the requested connections, it returns an error. When this connection goes out of scope, pending transactions are rolled back.
The third version of this method does everything the second version does. In addition, the commitflag parameter indicates what to do with pending transactions when this connection goes out of scope. If this parameter is false (the default), a pending transaction is rolled back. If this parameter is true, a pending transaction if committed.
示例
The following statement creates four connections to an Informix database named mydb on a server named myserver, with user name SYSTEM and password MANAGER. Pending transactions are rolled back at the end of a client request:
pool.connect("INFORMIX", "myserver", "SYSTEM", "MANAGER", "mydb", 4)
connected
Tests whether the database pool and all of its connections are connected to a database.
语法
connected()
参数
无。
返回
True if the pool (and hence a particular connection in the pool) is currently connected to a database; otherwise, false.
描述
The connected method indicates whether this object is currently connected to a database.
If this method returns false for a Connection object, you cannot use any other methods of that object. You must reconnect to the database, using the DbPool object, and then get a new Connection object. Similarly, if this method returns false for the database object, you must reconnect before using other methods of that object.
示例
示例 1: The following code fragment checks to see if the connection is currently open. If it's not, it reconnects the pool and reassigns a new value to the myconn variable.
if (!myconn.connected()) {
mypool.connect ("INFORMIX", "myserver", "SYSTEM", "MANAGER", "mydb", 4);
myconn = mypool.connection;
}
示例 2: The following example uses an if condition to determine if an application is connected to a database server. If the application is connected, the isConnectedRoutine function runs; if the application is not connected, the isNotConnected routine runs.
if(database.connected()) {
isConnectedRoutine() }
else {
isNotConnectedRoutine() }
connection
Retrieves an available connection from the pool.
语法
connection (name, timeout)
参数
返回
A new Connection object.
disconnect
Disconnects all connections in the pool from the database.
语法
disconnect()
参数
无。
返回
0 if the call was successful; otherwise, a nonzero status code based on any error message passed by the database. If the method returns a nonzero status code, use the associated majorErrorCode and majorErrorMessage methods to interpret the cause of the error.
描述
For the DbPool object, before calling the disconnect method, you must first call the release method for all connections in this database pool. Otherwise, the connection is still considered in use by the system, so the disconnect waits until all connections are released.
After disconnecting from a database, the only methods of this object you can use are connect and connected.
示例
The following example uses an if condition to determine if an application is connected to a database server. If the application is connected, the application calls the disconnect method; if the application is not connected, the isNotConnected routine runs.
if(database.connected()) {
database.disconnect() }
else {
isNotConnectedRoutine() }
majorErrorCode
Major error code returned by the database server or ODBC.
语法
majorErrorCode()
参数
无。
返回
The result returned by this method depends on the database server being used:
描述
SQL statements can fail for a variety of reasons, including referential integrity constraints, lack of user privileges, record or 表 locking in a multiuser database, and so on. When an action fails, the database server returns an error message indicating the reason for failure. The LiveWire Database Service provides two ways of getting error information: from the status code returned by various methods or from special properties containing error messages and codes.
Status codes are integers between 0 and 27, with 0 indicating a successful execution of the statement and other numbers indicating an error, as shown in
表 10.3 Database status codes.
表 10.3.
示例
This example updates the rentals 表 within a transaction. The updateRow method assigns a database status code to the statusCode variable to indicate whether the method is successful.
If updateRow succeeds, the value of statusCode is 0, and the transaction is committed. If updateRow returns a statusCode value of either five or seven, the values of majorErrorCode, majorErrorMessage, minorErrorCode, and minorErrorMessage are displayed. If statusCode is set to any other value, the errorRoutine function is called.
database.beginTransaction()
statusCode = cursor.updateRow("rentals")
if (statusCode == 0) {
database.commitTransaction()
}
if (statusCode == 5 || statusCode == 7) {
write("The operation failed to complete.<BR>"
write("Contact your system administrator with the following:<P>"
write("The value of statusCode is " + statusCode + "<BR>")
write("The value of majorErrorCode is " +
database.majorErrorCode() + "<BR>")
write("The value of majorErrorMessage is " +
database.majorErrorMessage() + "<BR>")
write("The value of minorErrorCode is " +
database.minorErrorCode() + "<BR>")
write("The value of minorErrorMessage is " +
database.minorErrorMessage() + "<BR>")
database.rollbackTransaction()
}
else {
errorRoutine()
}
majorErrorMessage
Major error message returned by database server or ODBC. For server errors, this typically corresponds to the server's SQLCODE.
语法
majorErrorMessage()
参数
无。
返回
A string describing that depends on the database server:
描述
SQL statements can fail for a variety of reasons, including referential integrity constraints, lack of user privileges, record or 表 locking in a multiuser database, and so on. When an action fails, the database server returns an error message indicating the reason for failure. The LiveWire Database Service provides two ways of getting error information: from the status code returned by connection and DbPool methods or from special connection or DbPool properties containing error messages and codes.
示例
See DbPool.majorErrorCode.
minorErrorCode
Secondary error code returned by database vendor library.
语法
minorErrorCode()
参数
无。
返回
The result returned by this method depends on the database server:
minorErrorMessage
Secondary message returned by database vendor library.
语法
minorErrorMessage()
参数
无。
返回
The string returned by this method depends on the database server:
storedProcArgs
Creates a prototype for a DB2, ODBC, or Sybase stored procedure.
语法
storedProcArgs (procName, type1, ..., typeN)
参数
返回
Nothing.
描述
This method is only for Sybase stored procedures.
This method provides the procedure name and the parameters for that stored procedure. Sybase stored procedures can accept parameters that are only for input ("IN"), only for output ("OUT"), or for both input and output ("INOUT").
You must create one prototype for each Sybase stored procedure you use in your application. Additional prototypes for the same stored procedure are ignored.
You can specify an INOUT parameter either as an INOUT or as an OUT parameter. If you use an INOUT parameter of a stored procedure as an OUT parameter, the LiveWire Database Service implicitly passes a NULL value for that parameter.
示例
Assume the inoutdemo stored procedure takes one input parameter and one input/output parameter, as follows:
create procedure inoutdemo ( @inparam int, @inoutparam int output)
as
if ( @inoutparam == null)
@inoutparam = @inparam + 1
else
@inoutparam = @inoutparam + 1
Assume execute the following code and then call outParameters(0), the result will be 101:
database.storedProcArgs("inoutdemo", "IN", "INOUT")
spobj= database.storedProc("inoutdemo", 6, 100);
answer = spobj.outParameters(0);
The value of answer is 101. On the other hand, assume you execute this code:
database.storedProcArgs("inoutdemo", "IN", "OUT")
spobj = database.storedProc("inoutdemo", 6, 100);
answer = spobj.outParameters(0);
In this case, the value of answer is 7.
toString
Returns a string representing the specified object.
语法
toString()
参数
无。
描述
Every object has a toString method that is automatically called when it is to be represented as a text value or when an object is referred to in a string concatenation.
You can use toString within your own code to convert an object into a string, and you can create your own function to be called in place of the default toString method.
This method returns a string of the following format:
db "name" "userName" "dbtype" "serverName"
where
The method displays an empty string for any of attributes whose value is unknown.
For information on defining your own toString method, see the Object.toString method.
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