Advanced Features. This section discusses in greater depth some of the SQLJ features introduced in the section . This discussion not only goes into greater detail but covers relatively advanced SQLJ functionality. Enviroment/user that connects to oracle. On unix this is normally the user enviroment that starts the webserver. SQL in the SQLJ program file into a Java source file with JDBC calls. It gives programmers a higher level of programmatic interface for - A Java. Overview of the Program Interface The program interface is the software layer between a database application and Oracle Database. The program interface: Provides a security barrier, preventing destructive access to the SGA by client user processes Acts as a. SQLJ is a deprecated working title for efforts to combine Java and SQL. It was a common effort started around 1997 by engineers from IBM, Oracle, Compaq, Informix, Sybase, Cloudscape and Sun Microsystems. It consists of the three parts: 0, 1 and 2. The connections depicted above represent a single connection for each program. For performance reasons your DBAs might set up 'Connection. Topics include the following. SQLJ. iterator class implementation and advanced functionality. Connection contexts are used to specify particular types of schemas for database connections. Execution contexts are used for status and control of SQL operations. Multithreading is discussed here because a key consideration in using multithreading with SQLJ is that multiple threads cannot use the same execution context. Each connection context class can be used for a particular type of schema, meaning that all the connections you define using a particular connection context class will use the same set of SQL objects (such as tables, views, and stored procedures). Note, however, that a connection context declaration does not define a type of schema that the connection context class is used for, and it is permissible to use the same connection context class for different schema types. Advanced SQLJ Functionality This section discusses in greater depth some of the SQLJ features introduced in the section. In addition to the methods specified and defined in the ConnectionContext interface, each connection context class defines the).
To avoid semantics errors when doing online checking, all of the SQL objects used in SQLJ statements that use a given connection context class must match SQL objects found in the exemplar schema you provide for online checking of that connection context class. Alternatively, if all of the SQLJ statements using a given connection context class use a set of SQL objects belonging to a single schema type, then you can provide a more meaningful exemplar schema which allows more accurate semantics- checking. In addition to any connection context classes that you declare, there is always a default connection context class: sqlj. Default. Context. You typically accomplish this by specifying a username, password, and database URL as input to the constructor of the connection context class. The connection context instance manages the set of SQL operations performed during the session. In this circumstance, however, one connection does not see changes from the other connection until you commit the changes. In the example above, both mctx. Remember that a connection context instance defines a particular connection, specifying a database URL, username, and password. A connection context class can be used for any number of such instances, typically to the same schema type. For clarity, this document always specifies whether it is discussing a connection context class or a connection context instance. In other words, you are using different sets of SQL objects such as tables, views, and stored procedures. While a SQLJ- generated connection context class has the same set of features as the Default. Context class, you can add code to customize a connection context class with additional functionality. It uses the default context to access a table of employees and a user- defined context to access employee department information. By using distinct contexts, it is possible for you to store the employee and department information in different schemas or even physically different databases. For more information, see the . This base class would be a feature of the particular SQLJ implementation you are using. In fact, its definition (aside from its package name) is the same as what can be generated by a SQLJ declaration. The following two statements will generate a definition that is identical to the actual definition of the Default. Context class (note the specification of public class). Default. Context. Instantiating a Connection Object. Continuing the preceding example, instantiate the Order. Entry. Ctx class with the following syntax. Order. Entry. Ctx my. Order. Conn = new Order. Entry. Ctx. (url, username, password, autocommit). Order. Entry. Ctx my. Order. Conn = new Order. Entry. Ctx. (. For example, in the following SQLJ statement, the connection object is my. Order. Conn from the previous example. This means that any executable statement that uses an instance of a declared connection context class must explicitly specify the appropriate connection instance, as shown above. It implicitly uses an object of the Default. Context class for one type of schema and uses an instance of the declared connection context class Dept. Context for another type of schema. As previously mentioned, this is just one of several ways you can construct a SQLJ connection context instance. This example is repeated in the . Additionally, it closes the underlying JDBC connection if you pass in CLOSE. It does not close the underlying JDBC connection if you pass in the boolean KEEP. If you do not pass in a parameter, the default is CLOSE. For more information, see the section . Then you could conveniently retrieve it using the get. Default. Context() method of the particular class. This would allow you, for example, to specify a connection context instance for a SQLJ executable statement as follows. My. Context. My. Context myctx. My. Context(url, user, password, auto- commit). For general information and syntax, see the section . More specifically, you might want the capability of a class that has get. Connection() functionality, but does not have other functionality of a connection context class. You can then declare a connection context class but expose only the get. Connection() functionality by assigning a connection context instance to a variable of the type Has. Connection instead of to a variable that has the type of your declared connection context class. This allows SQLJ semantics- checking to verify during translation that you are using your connection context instances correctly in your code. The type of schema specifies such properties as names and privileges associated with tables and views, the datatypes of their rows, and names and definitions of stored procedures. You accomplish this by setting the SQLJ - user, - password, and - url options. These schema examples are sometimes referred to as exemplar schemas. For information about these SQLJ options, see the section . For example, it must have tables, views, stored functions, and stored procedures with identical names and types, and with privileges set appropriately. In that case, SQLJ statements specifying connection objects of that connection context class are only semantically checked to the extent possible. The exemplar schema only furnishes the translator with an example of the type of schema that you use for a particular connection context class. An execution context instance is associated either implicitly or explicitly with each SQL operation in your SQLJ application. Every execution context is an instance of the Execution. Context class. So while the term connection context refers to a class that you have declared, the term execution context refers to an instance of the Execution. Context class. This document specifies connection context class, connection context instance, and execution context instance to avoid confusion. You can use different execution context instances in statements that use the same connection context instance, and vice versa. And you can use multiple connection context instances with a single execution context instance if you want the same set of SQL control parameters to apply to all of the connection context instances. This is described in the following section. This is convenient, as there are no input parameters for the Exection. Context constructor. Execution. Context my. Exec. Ctx = new Execution. Context(). You can then specify this execution context instance for use with any particular SQLJ statement, much as you would specify a connection context instance. The general syntax is as follows. The SQLWarning object is initially created for the first warning reported, and any subsequent warnings are chained to the same object. The SQLWarning object ultimately represents all warnings generated during the execution of the SQL operation and the subsequent outputting of parameters to the output host expressions. Zero (0) is returned if the last SQL operation was not a DML statement. The constant EXCEPTION. In such a case, this method returns the next result set, in a JDBC Result. Set object. Further calls move to and return subsequent result sets. This method implicitly closes each open result set that it had previously obtained. This method has no effect if no statement is currently being executed using this instance. The SQLJ runtime supports multiple threads either using separate connection context instances or sharing the same connection context instance. However, any use of multithreading in your SQLJ application is subject to the limitations of your JDBC driver or proprietary database access vehicle. Each statement, for example, may bind input parameters, then execute, then bind output parameters. With some JDBC drivers, special care must be taken not to intermingle these stages of different operations.). Whereas connection contexts can be safely shared between threads, execution contexts cannot. If an execution context is shared, the results of a SQL operation performed by one thread are visible in the other thread. If both threads are executing SQL operations, a race condition may occur in which the results of an execution in one thread are overwritten by the results of an execution in the next thread, before the first thread has processed the original results. For this reason, the Oracle SQLJ runtime is implemented so that if a thread attempts to execute a SQL operation using an execution context that is already being used to execute an operation in another thread, the second thread will be blocked until the first thread completes its operation. To avoid such blockages, each thread in your application must use a distinct execution context instance. This is required if you use multiple threads with the same connection context instance. However, each thread uses a distinct execution context instance. The run() method is the focus of this example. This sample is also repeated in the section . Classes implementing the Named. Using Network. Manager with the GNOME Graphical User Interface. In Red Hat Enterprise Linux 7, Network. Manager does not have its own graphical user interface (GUI). The network connection icon on the top right of the desktop is provided as part of the GNOME Shell and the Network settings configuration tool is provided as part of the new GNOME control- center GUI. The old nm- connection- editor GUI is still available for certain tasks. Connecting to a Network Using a GUI. There are two ways to access the Network settings window of the control- center application. When you click on the GNOME Shell network connection icon, you are presented with. Wired and Wi- Fi). Available Networks that Network. Manager has detected. Virtual Private Networks (VPNs); and. Network Settings menu entry. Clicking anywhere on the level of the button will toggle the state of the button. If you change the button from ON to OFF you will disconnect that network connection. The GNOME network menu, showing all available and connected- to networks. Configuring New and Editing Existing Connections. The Network settings window shows the connection status, its type and interface, its IP address and routing details, and so on. Configure Networks Using the Network Settings Window. The Network settings window has a menu on the left- hand side showing the available network devices or interfaces. This includes software interfaces such as for VLANs, bridges, bonds, and teams. On the right- hand side, the connection profiles are shown for the selected network device or interface. A profile is a named collection of settings that can be applied to an interface. Below that is a plus and a minus button for adding and deleting new network connections, and on the right a gear wheel icon will appear for editing the connection details of the selected network device or VPN connection. To add a new connection, click the plus symbol to open the Add Network Connection window and proceed to Section 2. Configuring a New Connection”. Configure Networks Using the Network Connection Details Window. Configuring a New Connection. In the Network settings window, click the plus sign below the menu to open the Add Network Connection window. This displays a list of connection types that can be added. Connecting to a Network Automatically. For any connection type you add or configure, you can choose whether you want Network. Manager to try to connect to that network automatically when it is available. Configuring Network. Manager to Connect to a Network Automatically When Detected. Press the Super key to enter the Activities Overview, type control network and then press Enter. The Network settings tool appears. If you have only one profile associated with the selected interface the gear wheel icon will be in the lower right- hand- side corner. The Network details window appears. The Network window changes to the identity view. Clear the check box if you do not want Network. Manager to connect automatically. If the check box is clear, you will have to select that connection manually in the network connection icon's menu to cause it to connect. System- wide and Private Connection Profiles. Network. Manager stores all connection profiles. A profile is a named collection of settings that can be applied to an interface. Network. Manager stores these connection profiles for system- wide use (system connections), as well as all user connection profiles. Access to the connection profiles is controlled by permissions which are stored by Network. Manager. See the nm- settings(5) man page for more information on the connection settings permissions property. The permissions correspond to the USERS directive in the ifcfg files. If the USERS directive is not present, the network profile will be available to all users. As an example, the following command in an ifcfg file will make the connection available only to the users listed: USERS=. In nm- connection- editor, there is the corresponding All users may connect to this network check box on the General tab, and in the GNOME control- center Network settings Identity window, there is the Make available to other users check box. Profiles that should be available at boot time cannot be private because they will not be visible until the user logs in. For example, if user user creates a connection profile user- em. Connect Automatically check box selected but with the Make available to other users not selected, then the connection will not be available at boot time. See the polkit(8) man page for more information on polkit. Changing a Connection to Be User- specific Instead of System- Wide, or Vice Versa. Depending on the system's policy, you may need root privileges on the system in order to change whether a connection is user- specific or system- wide. The Network settings tool appears. If you have only one profile associated with the selected interface the gear wheel icon will be in the lower right- hand- side corner. The Network details window appears. The Network window changes to the identity view. Configuring a Wired (Ethernet) Connection. To configure a wired network connection, press the Super key to enter the Activities Overview, type control network and then press Enter. The Network settings tool appears. A profile is a named collection of settings that can be applied to an interface. More than one profile can be created for an interface and applied as needed. The default profile cannot be deleted but its settings can be changed. You can edit the default Wired profile by clicking the gear wheel icon. You can create a new wired connection profile by clicking the Add Profile button. Connection profiles associated with a selected interface are shown on the right- hand side menu. The difference between these dialogs is that an existing connection profile has a Details and Reset menu entry. In effect, you are always editing a connection profile; the difference only lies in whether that connection previously existed or was just created by Network. Manager when you clicked Add Profile. Configuring the Connection Name, Auto- Connect Behavior, and Availability Settings. Many settings in the Editing dialog are common to all connection types, see the Identity view (or the General tab if using nm- connection- editor). Name — Enter a descriptive name for your network connection. This name will be used to list this connection in the menu of the Network window. The MTU value represents the size in bytes of the largest packet that the link- layer will transmit. This value defaults to 1. Select the VPN from the drop- down menu. If the profile was in use while being edited, power cycle the connection to make Network. Manager apply the changes. If the profile is OFF, set it to ON or select it in the network connection icon's menu. See Section 2. 5. Connecting to a Network Using a GUI” for information on using your new or altered connection. Configuring a Wi- Fi Connection. This section explains how to use Network. Manager to configure a Wi- Fi (also known as wireless or 8. Access Point. A padlock symbol indicates the access point requires authentication. If the access point is secured, a dialog prompts you for an authentication key or password. If there are multiple possibilities, Network. Manager guesses the security type and presents it in the Wi- Fi security drop- down menu. For WPA- PSK security (WPA with a passphrase) no choice is necessary. For WPA Enterprise (8. X) you have to specifically select the security, because that cannot be auto- detected. If you are unsure, try connecting to each type in turn. Finally, enter the key or passphrase in the Password field. Certain password types, such as a 4. WEP or 1. 28- bit WPA key, are invalid unless they are of a requisite length. The Connect button will remain inactive until you enter a key of the length required for the selected security type. To learn more about wireless security, see Section 2. Configuring Wi- Fi Security”. Connecting to a Hidden Wi- Fi Network. All access points have a Service Set Identifier (SSID) to identify them. However, an access point may be configured not to broadcast its SSID, in which case it is hidden, and will not show up in Network. Manager's list of Available networks. You can still connect to a wireless access point that is hiding its SSID as long as you know its SSID, authentication method, and secrets. The Network window appears. Select Wi- Fi from the menu and then select Connect to Hidden Network to cause a dialog to appear. If you have connected to the hidden network before, use the Connection drop- down to select it, and click Connect. If you have not, leave the Connection drop- down as , enter the SSID of the hidden network, select its Wi- Fi security method, enter the correct authentication secrets, and click Connect. Editing a Connection, or Creating a Completely New One. You can edit an existing connection that you have tried or succeeded in connecting to in the past by opening the Wi- Fi page of the Network dialog and selecting the gear wheel icon to the right of the Wi- Fi connection name. If the network is not currently in range, click History to display past connections. When you click the gear wheel icon the editing connection dialog appears. The Details window shows the connection details. If the SSID is not in range, see Section 2. Connecting to a Hidden Wi- Fi Network”. If the SSID is in range, the procedure is as follows. Press the Super key to enter the Activities Overview, type control network and then press Enter. The Network settings tool appears. A padlock symbol indicates a key or password is required. The following settings are available. The Service Set Identifier (SSID) of the access point (AP). This field is blank by default, and you are able to connect to a wireless access point by SSID without having to specify its BSSID. If the BSSID is specified, it will force the system to associate to a specific access point only. It is not displayed by Network. Manager. MAC address. Select the MAC address, also known as a hardware address, of the Wi- Fi interface to use.
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