How do I print a list of strings contained within another list in iReport?

I am creating a simple reporting program using java and iReport (from jasper), which is supposed to create a report in pdf showing PCs with their IP address, their location, whether it's idle or not at the moment (handled by another system), and a list of projects it is currently attached to (managed elsewhere, too).

I'm using iReport for this matter, and have created a dummy collection generating class as follows:

public class PCReports {

    public static java.util.Collection PC_collection;
    public static java.util.Collection generateCollection() {

        PC_collection = new ArrayList<PCLineDTO>();
        PCLineDTO line = new PCLineDTO();
        line.setIP("192.168.1.1");
        line.setLab("location");
        line.setActive(true);
        line.addProjectName("project1");
        line.addProjectName("project2");
        line.addProjectName("project3");
        PC_collection.add(line);

        line = new PCLineDTO();
        line.setIp("192.168.1.2");
        line.setLab("location2");
        line.setActive(false);
        line.addProjectName("project1");
        line.addProjectName("project2");
        PC_collection.add(line);

        return PC_collection;
    }
}

The entity class in this case being:

public class PCLineDTO {
    private String ip;
    private String lab;
    private Boolean active;
    private ArrayList<String> projects;
}

After some searching around the Internet, I found a way to do something similar, using subreports.

The thing is, I don't know how to print a collection of strings passed as a dataSource to this subreport.

In the examples I found on the Internet, for each item in the master collection, the subreports were passed a collection of objects -with their own getter methods for each attribute- instead of a collection开发者_StackOverflow社区 of strings as is the case here. In those cases, they accessed the values they needed to use via the iReport syntax, which I was not able to use, for example:

$F{project}

Since iReport looks for a getProject method contained within the objects it receives, but in this case it's a simple String object (without a getProject method, as it were).

Use a subreport or a subdataset.

Pass the subreport a collection datasource

JRBeanCollectionDataSource($F{Projects})

Then in the new subreport create a new field called "_THIS" exactly, this means the bean in the collection passed is the same as the value i want

For more info, check the source code of the class here: JRAbstractBeanDataSource

Note: this is available in JasperReport 3.0.0 im not sure if it exists in previous builds. Hope this helps

Update: just checked the SVN, seems like this feature is implemented in JasperReports 2.0.0

Interesting. I think you'd better use the List, and then define getName() on the Project class. Then in the subreport define a variable "name". It will work this way, and it will allow you to add easily additional information, like project duration, team-lead, etc.

As Bozho says, in case proyects was an array of complex object you should reference it as a field of type java.util.Collection an then pass it to the inner subreport the same way medopal indicates. And don´t put the _THIS field.

To elaborate on this without using _THIS: let's say a java bean has a list of subBeans and this subBean has a complex format and we want to print each subBean in a custom way. I quote an example where the subDataset element is on the report level and the componentElement is in the detail band:

<subDataset name="ListOfSubBeans" uuid="66c86e41-c565-4f18-bccf-1a1b2a567585">
    <field name="subBeanField_1" class="java.lang.String">
        <fieldDescription><![CDATA[subBeanField_1]]></fieldDescription>
    </field>
</subDataset>

...

        <componentElement>
            <reportElement x="780" y="0" width="100" height="30" uuid="f73864b9-46dd-4adb-8dad-a6bd8dfae64e">
                <property name="net.sf.jasperreports.export.headertoolbar.table.name" value=""/>
            </reportElement>
            <jr:list xmlns:jr="http://jasperreports.sourceforge.net/jasperreports/components" xsi:schemaLocation="http://jasperreports.sourceforge.net/jasperreports/components http://jasperreports.sourceforge.net/xsd/components.xsd" printOrder="Vertical">
                <datasetRun subDataset="ListOfSubBeans" uuid="a8dd1c2b-3ac0-4ffa-b9d0-08e4890e199a">
                    <dataSourceExpression><![CDATA[new net.sf.jasperreports.engine.data.JRBeanCollectionDataSource($F{listOfSubBeans})]]></dataSourceExpression>
                </datasetRun>
                <jr:listContents height="30" width="100">
                    <textField>
                        <reportElement x="0" y="0" width="100" height="30" uuid="61700c18-6bb9-45da-a235-b76b9f76a2ea"/>
                        <textFieldExpression><![CDATA[$F{subBeanField_1}]]></textFieldExpression>
                    </textField>
                </jr:listContents>
            </jr:list>
        </componentElement>

...

So, the master dataset has declared that the master bean has a member variable that is a list: listOfSubBeans. This java.util.List is used to feed the datasource of the jr:list, while the fields of the jr:list are declared using a subDataset called ListOfSubBeans (pay attention to case sensitivity).