Importing Parameter Values

When you view a report with parameters, the Enter Parameter Values dialog will be displayed, showing the parameters the report uses for you to input values. The default values shown in the dialog are fixed at development time. However, showing a default, fixed value often is not useful to users.

JReport provides an interface for importing different default values from an outside class file so that the default values can be specified flexibly. There is only one method for this interface: public Hashtable promptValues(String paramsName[]);

Reference: JReport Javadoc jet.util.ImportParamValues interface in <install_root>\help\api.

The following are the general steps for importing parameter values from a class file:

Define a Java class file. For help, see the sample program ParamTest.java and TestParamList.java in <install_root>\help\samples\APIParameter. To import parameter values, implement the interface jet.util.ImportParamValues in your Java file. The class definition may be as follows:

package help.;
import java.util.*;
import jet.util.*;
public class ParamTest implements ImportParamValues
{
    public ParamTest()
    {
        //Class body
    }
    public Hashtable promptValues(String paramsName[])
    {
        //Class body
    }
}

The following explains the code:

The package name can be defined by yourself. In our sample code, we use help as the package name.
Since the interface ImportParamValues is in the package jet.util, you will have to import the class package jet.util.*.
A public constructor method without parameters is required.

Compile the Java file to generate the class file.

Append the class path to the ADDCLASSPATH variable of the file setenv.bat/setenv.sh in <install_root>\bin for both JReport Designer and JReport Server.

Start JReport Designer with the modified batch file.

Open the report with the parameter value that you want to import.

In the Report Inspector, set the property Import Parameter Values of the report to be the class name that you just generated with the package name, and set Parameter List Auto to false.

The following two examples explain how to import parameter values and what you should be aware of while using this feature.

Example 1: Importing from a database

In the sample program ParamTest.java in <install_root>\help\samples\APIParameter, different values were assigned to the parameter p_StartDate by accessing values from an HSQL database. We will create a report based on a query using this parameter in the query condition and use this report to explain how to import parameter values from a database, so that you do not need to type in the values one by one while specifying the parameter default value (note that in this example we assume your JReport Designer is installed in the default path, that is C:\JReport\Designer).

Note that in the sample ParamTest.java, we use the method compareToIgnoreCase() to compare the parameter name in the class file with the one in your report. This method is not case sensitive when performing the comparison.

Example 2: Importing from a class file

In addition to Example 1, another example of applying the feature of importing parameter values is to specify your required default values. When you group/sort data dynamically with a parameter, when viewing the report, a dialog will be displayed, in which you will find many default values in the drop-down list. However, since you do not need so many values with which to group/sort, you can specify your required default values in a Java class, and then import them. For help, refer to the sample program TestParamList.java in <install_root>\help\samples\APIParameter.

To specify the default parameter values in a class file and then import them, follow the steps below:

Notes:

You need to ensure that the parameter format in the class file is consistent with that in JReport, specifically, that the parameter format used in the class file is parsed when viewing the report so that the correct data records will be returned.
When you implement the interface jet.util.ImportParamValues and use its function promptValues(), ensure that:
- The parameter of this function is a String array which contains the names of the parameters.
- The return value of this method is a Hashtable, its keys are parameter names used in the report and its values are vector objects which contain the parameter values.
When there are subreports in a primary report, setting the properties Import Parameter Value and Parameter List Auto will not affect them. That is, you have to set these properties in the primary report and subreports separately.
If you want to use a parameter as grouping/sorting criteria, you will need to make sure that the parameter values are within the columns used in the report's query. In addition, the name should be consistent with the column names defined in the catalog. For example, the query of the report joins two tables: Orders and Orders Detail. In the Catalog Manager, expand the query used by the report. You will then see all the columns from the two tables. Make sure that the values returned are within them and consistent with the column names.