Java Operator Sample

About This Sample

The StringCase.sbapp sample application uses a Java operator to change the case of strings. This is then used to implement case-insensitive query table lookups.

This topic describes the Java operator sample, which includes a StreamBase application and a Java class that extends*.

For details about how StreamBase used the API to extend*, see Using the StreamBase Java Operator Wizard in the API Guide. For information about importing a JAR that contains a Java Operator in StreamBase Studio, and then selecting an Operator class from that JAR, see Using Java Operators in the Authoring Guide.

For details about using custom icons with your Java operators, see the Java Client library documentation for getIconResource in


The Java code in this sample is delivered only in source code form. To build the code, you must load the sample into StreamBase Studio, which automatically builds the Java code.

Importing This Sample into StreamBase Studio

In StreamBase Studio, import this sample with the following steps:

  • From the top menu, select FileLoad StreamBase Sample.

  • Select javao to narrow the list of options.

  • Select javaoperator from the Extending StreamBase category.

  • Click OK.

StreamBase Studio creates a project for the sample.

Running StringCase.sbapp in StreamBase Studio

  1. In the Project Explorer, notice the src/main/java folder in the sample_javaoperator project. This directory contains sample.StringCase under the package folder, which extends

  2. In the Project Explorer, open the sample you just loaded.

  3. Open the src/main/eventflow folder.

  4. Open the package folder (most samples contain a single package folder. Open the top-level package folder if your sample contains more than one folder).

  5. Open the StringCase.sbapp application file.

  6. Click the Java1 operator in the canvas to open its Properties view. In the Parameters tab, notice that the string conversion type (by default) is set to Lowercase. Change this setting to Uppercase. Do the same for the Java2 operator.

  7. Select the StringCase.sbapp tab in the EventFlow Editor, then click the Run button. The application starts and Studio switches to the SB Test/Debug perspective.

    If you see red marks, wait a moment for the project in Studio to load its features.

    If red marks do not resolve themselves in a moment, select the project and right-click MavenUpdate Project from the context menu.

  8. Select the Manual Input view. Select InputPrice from the Input Stream list.

  9. In the symbol field, enter ibm, and in the price field, enter 120, and click Send Data.

  10. In the Output Streams view, notice that in OutputStream1, after the write to the Query Table, the symbol string is IBM in uppercase.

  11. Type symbol Orcl, price 40, and click Send Data.

  12. In the Manual Input view, select PriceQuery from the Input Stream list.

  13. Type symbol ibm, and click Send Data. The price, 120, is displayed in the Output Streams view.

  14. Type symbol oRcL in mixed case, and click Send Data. The price, 40, is displayed in the Output Streams view. Notice that the table lookup was successful, because the string is stored as uppercase, despite the mixed-case initial input.

  15. When done, press F9 or click the Stop Running Application button.

Sample Location

When you load the sample into StreamBase Studio, Studio copies the sample project's files to your Studio workspace, which is normally part of your home directory, with full access rights.


Load this sample in StreamBase Studio, and thereafter use the Studio workspace copy of the sample to run and test it, even when running from the command prompt.

Using the workspace copy of the sample avoids permission problems. The default workspace location for this sample is:


See Default Installation Directories for the default location of studio-workspace on your system.