Java Database Class
Last updated
Last updated
To use the SILK Java Database Class in your own Java class or JSP code you have to import the com.oopsclick.silk.dbo.* class package together with other classes you may need.
For a java class use: import com.oopsclick.silk.dbo.*;
For a JSP code use: <%@ page import="com.oopsclick.silk.dbo.*" %>
This package provides multiple classes to submit and retrieve data between the application and the database. The main class is the DataProvider.
The DataProvider is the only class needed to connect to an ORM object and use its methods to update data into the connected database. A DataProvider can only be connected to one ORM object. However an application, or program, can contain multiple DataProviders connected to different ORM objects.
There are multiple ways to use a DataProvider in an application and it is up to the programer to decide the level of complexity based on application requirements. This documentation will start with the simple way to use the DataProvider and scale to a more complex scenarios.
A DataProvider is connected to an ORM object. The ORM Object path has to be provided during the class instantiation. In order to easily recognize a DataProvider it is suggested to add the postfix "DP" at the end of the object name.
If you know the exact location of the ORM file use this constructor.
If you are using the the SILK-Builder environment to define a DataProvider in a Java code inside a JSP file use this constructor.
In the example above the DataProvider dataDP is connected to the testPerson.orm object. All the operation are going to be related to this ORM Object configuration. Read the chapter to understand how the ORM is configured.
To extract information from the database the select() method is used. This method will call a SQL SELECT command store in a <sqlSelect> tag in the testPerson.orm object. The select() method return the number of record extracted after executing the SQL SELECT command.
The select() method can received a selectName parameter, select(selectName), which allows to call different SQL SELECT commands store in the ORM Object. For example:
In this example the select("onlyFemales") command will call for the SQL SELECT stored in the <sqlSelect name="onlyFemales" > tag in the ORM Object.
After the select() method is executed the data extracted is stored in the DataProvider. One way to get access to the data is by looping its records and calling the information using the getItemAt() method. The loops is usually a for() command which will use as top limit the number of records returned by the select() command. It should start counting from 0 using single increments.
There are several methods to extract the data from a record depending in how the programer wants to use the data. The basic one is getItemAt() method which returns data with the type Object. In this case date data has to be cast to the type in which the programers requirements. This method received two parameters: the index position of the record to accessed, and the column's name of the information to be extracted. For Example:
There are method which will return data in specific types: getStringItem(), getIntItem(), getDoubleItem(), getLongItem(), and getDateItem(). These are use in this way:
Ther are methods retuning string formatted values with parameters to support formatting templates: getIntStringItem(), getDoubleStringItem(), and getDateStringItem(). These are used in this way:
In the cases when the returned data is expected to be only one row the code could look like this:
Notice that in this case the method does not received the index, only the column. Under this conditions the method will always return the first row value. If the SQL SELECT does not return a row the method will return null.
To insert a record in the database the information has first be loaded in the DataProvider using the setFormItem() method, and later executing the insert() method. The setFormItem() method receives to parameters: column and value. The insert() method return an integer with the number of affected rows. The programer does not have to send the primary key except if the ORM Object table is configure to pkMode="value". The generated primary key can be extracted using the same methods explained before. It is a good practice to clean the form values using the method cleanForm() before loading values.
The code to insert data looks like this:
To update a record follows a similar process as the insert process. The difference is that in this case the primary key has to be provided together with the data to be modify. and execute the update() method.
The following code updates the columns phone and email:
To delete a record only the primary key has to be provided, and the delete() method executed.