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jvx:reference [2020/06/15 09:10] cduncan [Application Basics] |
jvx:reference [2020/06/15 09:57] cduncan [Accessing the Data With Strings] |
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This example demonstrates how a simple launcher is implemented and why it is necessary to have a launcher in the first place. Compared with the “[[#jvx|JVx]] are of course a lot more complex than these examples, that is because they implement all the required functionality and also take care of a lot of boiler plate operations. It is taking care of all technology specific code and allows to keep your application free from knowing about the platform it runs on. | This example demonstrates how a simple launcher is implemented and why it is necessary to have a launcher in the first place. Compared with the “[[#jvx|JVx]] are of course a lot more complex than these examples, that is because they implement all the required functionality and also take care of a lot of boiler plate operations. It is taking care of all technology specific code and allows to keep your application free from knowing about the platform it runs on. | ||
- | ====== Data Books ====== | + | ====== Databooks ====== |
- | Let’s talk about data books, which allow access to data without any effort. | + | Let’s talk about databooks, which allow access to data without any effort. |
===== What is it? ===== | ===== What is it? ===== | ||
- | DataBooks are an active model, which allow you to directly query and manipulate the data. Contrary to many other systems, [[https://sourceforge.net/projects/jvx/|JVx]] does not map the data into objects, but allows you to directly access it in a table-like fashion exposing columns, rows, and values. | + | Databooks are an active model that allow you to directly query and manipulate the data. Contrary to many other systems, [[https://sourceforge.net/projects/jvx/|JVx]] does not map the data into objects, but allows you to directly access it in a table-like fashion exposing columns, rows, and values. |
One could say that it is like a three dimensional array with these dimensions: | One could say that it is like a three dimensional array with these dimensions: | ||
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The row definition defines what columns are available in the row and stores some additional information about them, like the names of the [[https://en.wikipedia.org/wiki/Unique_key|primary key]] columns. You can think of the row definition as the headers of a table. | The row definition defines what columns are available in the row and stores some additional information about them, like the names of the [[https://en.wikipedia.org/wiki/Unique_key|primary key]] columns. You can think of the row definition as the headers of a table. | ||
- | Its creation and usage is rather simple, and, if you’re working with RemoteDataBooks there is no need to create one at all, as it is automatically created when the data book is opened. A row definition holds and manages column definitions, which define the columns. | + | Its creation and usage is rather simple, and, if you’re working with RemoteDataBooks there is no need to create one at all, as it is automatically created when the databook is opened. A row definition holds and manages column definitions, which define the columns. |
<code java> | <code java> | ||
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The data page is basically a list of data rows. It also holds its own row definition, which is shared with all the contained data rows. | The data page is basically a list of data rows. It also holds its own row definition, which is shared with all the contained data rows. | ||
- | The main usage of data pages is to allow paging in a master/detail relationship. If the master selects a different row, the detail data book selects the related data page. | + | The main usage of data pages is to allow paging in a master/detail relationship. If the master selects a different row, the detail databook selects the related data page. |
- | ===== Data Book ===== | + | ===== Databook ===== |
- | The data book is the main model of [[https://sourceforge.net/projects/jvx/|JVx]], it provides direct access to its current data page and data row by extending from IDataRow and IDataPage. | + | The databook is the main model of [[https://sourceforge.net/projects/jvx/|JVx]], it provides direct access to its current data page and data row by extending from IDataRow and IDataPage. |
- | By default, the data book holds one data page and only has multiple data pages if it is the detail in a master/detail relationship. | + | By default, the databook holds one data page and only has multiple data pages if it is the detail in a master/detail relationship. |
===== Usage Example ===== | ===== Usage Example ===== | ||
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==== Accessing the Data With Strings ==== | ==== Accessing the Data With Strings ==== | ||
- | One of the major advantages of the data book concept is that there is no need to create new classes to represent each table, view, or query result. One can always use the data book directly and easily, and model changes don’t necessitate changes on the client side. The downside to this approach is that we lose compile time checks because we access the data dynamically. However, this can be mitigated by using [[https://marketplace.eclipse.org/content/eplug-jvx|EPlug, an Eclipse plugin]] which provides compile time checks and many more features. | + | One of the major advantages of the databook concept is that there is no need to create new classes to represent each table, view, or query result. One can always use the databook directly and easily, and model changes don’t necessitate changes on the client side. The downside to this approach is that we lose compile time checks because we access the data dynamically. However, this can be mitigated by using [[https://marketplace.eclipse.org/content/eplug-jvx|EPlug, an Eclipse plugin]] which provides compile time checks and many more features. |
==== No Primitives, Objects Only ==== | ==== No Primitives, Objects Only ==== | ||
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frame.eventWindowClosed().addListener(() -> System.exit(0)); | frame.eventWindowClosed().addListener(() -> System.exit(0)); | ||
</code> | </code> | ||
- | We can start to create and manipulate the GUI. In this case we are building a simple window with a label inside. Last but not least, we make sure that the JVM will exit when the window is closed. | + | We can start to create and manipulate the GUI. In this case, we are building a simple window with a label inside. Lastly, we make sure that the JVM will exit when the window is closed. |
A very good example and showcase for that is the [[https://github.com/sibvisions/jvx.kitchensink|JVx Kitchensink]]. | A very good example and showcase for that is the [[https://github.com/sibvisions/jvx.kitchensink|JVx Kitchensink]]. | ||
- | That’s it. That is the most simple way to start a [[https://sourceforge.net/projects/jvx/|JVx]] application. We can use all controls, and we can use ''%%MemDataBook%%''s without any problem or limitation. Best of all, we can simply switch to another technology by using another factory. | + | That’s it! That is the most simple way to start a [[https://sourceforge.net/projects/jvx/|JVx]] application. We can use all controls, and we can use ''%%MemDataBook%%''s without any problem or limitation. Best of all, we can simply switch to another technology by using another factory. |
- | ===== Anatomy of a remote JVx application ===== | + | ===== Anatomy of a Remote JVx Application ===== |
- | Of course [[https://sourceforge.net/projects/jvx/|JVx]] wouldn’t be that useful if it would just provide static GUI components. Now, to explain what else is required for a remote [[https://sourceforge.net/projects/jvx/|JVx]] application I have to go far afield, so let’s head down the rabbit hole. | + | Of course, [[https://sourceforge.net/projects/jvx/|JVx]] wouldn’t be that useful if it would just provide static GUI components. Now, to explain what else is required for a remote [[https://sourceforge.net/projects/jvx/|JVx]] application, I have to go far afield, so let’s head down the rabbit hole. |
{{:jvx:reference:jvx-client-server.png?nolink| Layers}} | {{:jvx:reference:jvx-client-server.png?nolink| Layers}} | ||
- | What you are seeing here is a rough sketch of how the architecture of [[https://sourceforge.net/projects/jvx/|JVx]] looks like. Let’s walk through the image step by step. We will look at each successive layer and work our way from the database on the server to the databook on the client. | + | What you are seeing here is a rough sketch of how the architecture of [[https://sourceforge.net/projects/jvx/|JVx]] looks like. Let’s walk through the image step by step. We will look at each successive layer and work our way from the database on the server to the data book on the client. |
- | ==== DBAccess, accessing a database ==== | + | ==== DBAccess, Accessing a Database ==== |
Accessing a database is easy when using ''%%DBAccess%%''. All we must do is to set the [[https://en.wikipedia.org/wiki/Java_Database_Connectivity|JDBC]] URL of the server and connect to it: | Accessing a database is easy when using ''%%DBAccess%%''. All we must do is to set the [[https://en.wikipedia.org/wiki/Java_Database_Connectivity|JDBC]] URL of the server and connect to it: | ||
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dbAccess.open(); | dbAccess.open(); | ||
</code> | </code> | ||
- | As a note, the instance returned by ''%%getDBAccess(...)%%'' is the database specific ''%%DBAccess%%'' extension, which does know how to handle its database. | + | As a note, the instance returned by ''%%getDBAccess(...)%%'' is the database-specific ''%%DBAccess%%'' extension, which knows how to handle its database. |
- | We can of course use ''%%DBAccess%%'' to directly access the database: | + | We can, of course, use ''%%DBAccess%%'' to directly access the database: |
<code java> | <code java> | ||
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List<Bean> data = dbAccess.executeQuery("select * from SOME_TABLE"); | List<Bean> data = dbAccess.executeQuery("select * from SOME_TABLE"); | ||
</code> | </code> | ||
- | …or manipulate the database, or query information about the database or execute procedures or do anything else. | + | …or manipulate the database, query information about the database, execute procedures, or anything else! |
- | ==== DBStorage, preparing the database access for databooks ==== | + | ==== DBStorage, Preparing the Database Access for Databooks ==== |
- | The downside of using DBAccess is that everything must be database specific. To become database agnostic we must use ''%%DBStorage%%''. ''%%DBStorage%%'' does not care which database it is connected to and can operate on any of them: | + | The downside of using DBAccess is that everything must be database-specific. To become database-neutral, we must use ''%%DBStorage%%''. ''%%DBStorage%%'' does not care which database it is connected to and can operate on any of them: |
<code java> | <code java> | ||
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storage.open(); | storage.open(); | ||
</code> | </code> | ||
- | We can use this to insert, update, delete and fetch data. Additionally the ''%%DBStorage%%'' does retrieve and manage the metadata of the table we’ve set, which means that we can query all column names, what type they are, we can even access the indexes and the default values. Short, the ''%%DBStorage%%'' leaves little to be desired when it comes to operating on a database. | + | We can use this to insert, update, delete and fetch data. Additionally, the ''%%DBStorage%%'' does retrieve and manage the metadata of the table we’ve set, which means that we can query all column names, what type they are, we can even access the indexes and the default values. Short, the ''%%DBStorage%%'' leaves little to be desired when it comes to operating on a database. |
- | If we query data from the ''%%DBStorage%%'' we receive a List of rows. The rows are are either represented as ''%%Object%%'' array, ''%%IBean%%'' or a POJO and we can easily manipulate the data, like this: | + | If we query data from the ''%%DBStorage%%'', we receive a list of rows. The rows are either represented as ''%%Object%%'' array, ''%%IBean%%'', or a POJO, and we can easily manipulate the data, like this: |
<code java> | <code java> | ||
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} | } | ||
</code> | </code> | ||
- | As one can see, it looks quite familiar to the DataBook, which isn’t a coincidence. The ''%%DBStorage%%'' “powers” the DataBooks on the server side, a DataBook will get its data from and will send its modified data to the ''%%DBStorage%%''. | + | As one can see, it looks quite familiar to the DataBook, which isn’t a coincidence. The ''%%DBStorage%%'' “powers” the databooks on the server side, a databook will get its data from and will send its modified data to the ''%%DBStorage%%''. |
- | I’ve been using the ''%%DBStorage%%'' here as an example, but actually the Storage is not dependent on a database. ''%%IStorage%%'' can be implemented to provide any sort of data provider, like reading from an XML or JSON file, scraping data from a website, fetching data from a different process or reading it directly from a hardware sensor. | + | I’ve been using the ''%%DBStorage%%'' here as an example, but actually the storage is not dependent on a database. ''%%IStorage%%'' can be implemented to provide any sort of data provider, like reading from an XML or JSON file, scraping data from a website, fetching data from a different process, or reading it directly from a hardware sensor. |
==== Life Cycle Objects, the business objects with all the logic ==== | ==== Life Cycle Objects, the business objects with all the logic ==== |