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## 6.34. < rich:columns >

### 6.34.1. Description

The <rich:columns> is a component, that allows you to create a dynamic set of columns from your model.

Figure 6.41. <rich:columns> component

### 6.34.2. Key Features

- Highly customizable look and feel

- Dynamic tables creation

- Possibility to combine columns with the help of "colspan" and "breakBefore"

- Possibility to combine rows with the help of "rowspan"

- Sorting column values

- Filtering column values

Table 6.126. rich : columns attributes

Attribute Name | Description
--- | ---
begin | The first iteration item
breakBefore | if "true" next column begins from the first row
colspan | Corresponds to the HTML colspan attribute
columns | Number of columns to be rendered
comparator | Defines value binding to the comparator that is used to compare the values
dir | Direction indication for text that does not inherit directionality. Valid values are "LTR" (left-to-right) and "RTL" (right-to-left)
end | The last iteration item
filterBy | Defines iterable object property which is used when filtering performed.
filterEvent | Event for filter input that forces the filtration (default value is "onchange")
filterExpression | Attribute defines a bean property which is used for filtering of a column
filterMethod | This attribute is defined with method binding. This method accepts on Object parameter and return boolean value
filterValue | Defines current filtering value
footerClass | Space-separated list of CSS style class(es) that are be applied to any footer generated for this table
headerClass | Space-separated list of CSS style class(es) that are be applied to any header generated for this table
id | Every component may have a unique id that is automatically created if omitted
index | The current counter
label | Column label for drag indicator. Usable only for extendedDataTable component
lang | Code describing the language used in the generated markup for this component
rendered | If "false", this component is not rendered
rowspan | Corresponds to the HTML rowspan attribute
selfSorted | Manages if the header of the column is clickable, icons rendered and sorting is fired after click on the header. You need to define this attribute inside <rich:dataTable> component
sortable | Boolean attribute. If "true" it's possible to sort the column content after click on the header. Default value is "true"
sortBy | Attribute defines a bean property which is used for sorting of a column
sortExpression | DEPRECATED(use sortBy)Attribute defines a bean property which is used for sorting of a column
sortIcon | Defines sort icon
sortIconAscending | Defines sort icon in ascending order
sortIconDescending | Defines sort icon in descending order
sortOrder | SortOrder is an enumeration of the possible sort orderings.
style | CSS style(s) is/are to be applied when this component is rendered
styleClass | Corresponds to the HTML class attribute
title | Advisory title information about markup elements generated for this component
value | The current value for this component
var | The current variable
visible | The attribute is used to define whether the component is visible or not. The default value is "true".
width | Attribute defines width of column.

Table 6.127. Component identification parameters

Name | Value
--- | ---
component-type | org.richfaces.Column
tag-class | org.richfaces.taglib.ColumnsTagHandler

### 6.34.3. Creating the Component with a Page Tag

To create the simplest variant on a page use the following syntax:

Example:

    ...

    <rich:dataTable value="#{capitalsBean.capitals}" var="cap">

            <rich:columns value="#{capitalsBean.labels}" var="col" index="index">

                    <h:outputText value="#{cap[index]}" />

            </rich:columns>

    </rich:dataTable>

    ...

### 6.34.4. Creating the Component Dynamically Using Java

Example:

    import org.richfaces.component.html.HtmlColumns;

    ...

    HtmlColumns myColumns = new HtmlColumns();

    ...

### 6.34.5. Details of Usage

The <rich:columns> component gets a list from data model and outputs corresponding set of columns inside <rich:dataTable> on a page. It is possible to use "header" and "footer" facets with <rich:columns> component.

The "value" and "var" attributes are used to access the values of collection.

The simple example is placed below.

Example:

    ...

    <rich:dataTable value="#{capitalsBean.capitals}" var="cap">

            <rich:columns value="#{capitalsBean.labels}" var="col" index="index">

                    <f:facet name="header">

                            <h:outputText value="#{col.text}" />

                    </f:facet>

             <h:outputText value="#{cap[index]}" />

             <f:facet name="footer">

                     <h:outputText value="#{col.text}" />

             </f:facet>

            </rich:columns>

    </rich:dataTable>

    ...

The "columns" attribute defines the count of columns.

The "rowspan" attribute defines the number of rows to be displayed. If the value of this attribute is zero, all remaining rows in the table are displayed on a page.

The "begin" attribute contains the first iteration item. Note, that iteration begins from zero.

The "end" attribute contains the last iteration item.

With the help of the attributes described below you can customize the output, i.e. define which columns and how many rows appear on a page.

Example:

    ...

    <rich:dataTable value="#{capitalsBean.capitals}" var="cap">

            <rich:columns value="#{capitalsBean.labels}" var="col" index="index" rowspan="0" columns="3" begin="1" end="2">

                    <f:facet name="header">

                            <h:outputText value="#{col.text}" />

                    </f:facet>

                    <h:outputText value="#{cap[index]}" />

            </rich:columns>

    </rich:dataTable>

    ...

In the example below, columns from first to second and all rows are shown in the <rich:dataTable> .

The result is:

Figure 6.42. Generated <rich:columns> with columns from first to second and all rows

The <rich:columns> component does not prevent to use <rich:column> . In the following example one column renders in any way and another columns could be picked from the model.

Example:

    ...

    <rich:dataTable value="#{rowBean.rows}" var="row">

            <rich:column>

                    <h:outputText value ="#{row.columnValue}"/>

            </rich:column>

            <rich:columns value="#{colBean.columns}" var="col">

                    <f:facet name="header">

                            <h:outputText value="#{col.header}"/>

                    </f:facet>

                    <h:outputText value="#{row.columnValue}"/>

                    <f:facet name="footer">

                            <h:outputText value="#{col.footer}"/>

                    </f:facet>

            </rich:columns>

    </rich:dataTable>

    ...

In order to group columns with text information into one row, use the "colspan" attribute, which is similar to an HTML one. In the following example the third column contains 3 columns. In addition, it's necessary to specify that the next column begins from the first row with the help of the `breakBefore = "true"` .

Example:

    ...

    <rich:dataTable value="#{columns.data1}" var="data">

            <rich:column>

                    <h:outputText value="#{column.Item1}" />

            </rich:column>

            <rich:column>

                    <h:outputText value="#{column.Item2}" />

            </rich:column>

            <rich:column>

                    <h:outputText value="#{column.Item3}" />

            </rich:column>

            <rich:columns columns="3" colspan="3" breakBefore="true">

                    <h:outputText value="#{data.str0}" />

            </rich:columns>

    </rich:dataTable>

    ...

The same way is used for columns grouping with the "rowspan" attribute that is similar to an HTML. The only thing to add in the example is an instruction to move onto the next row for each next after the second column.

Example:

    ...

    <rich:dataTable value="#{columns.data1}" var="data">

            <rich:columns columns="2" rowspan="3">

                    <h:outputText value="#{data.str0}" />

            </rich:columns>

            <rich:column>

                    <h:outputText value="#{column.Item1}" />

            </rich:column>

            <rich:column  breakBefore="true">

                    <h:outputText value="#{column.Item2}" />

            </rich:column>

            <rich:column  breakBefore="true">

                    <h:outputText value="#{column.Item3}" />

            </rich:column>

    </rich:dataTable>

    ...

## Note:

The <rich:columns> tag is initialized during components tree building process. This process precedes page rendering at "Render Response" JSF phase. To be rendered properly the component needs all it variables to be initialized while the components tree is being building. A javax.servlet.jsp.JspTagException occurs if <rich:columns> uses variables passed from other components, if these variables are initialized during rendering. Thus, when <rich:columns> is asking for such variables they do not already exist. Use <c:forEach> JSP standard tag as workaround. Compare two examples below.

This code calls the exception:

    ...

    <rich:dataTable value="#{bean.data}" var="var">

              <rich:columns value="#{var.columns}">

                 ...

              </rich:columns>

    </rich:dataTable>

    ...

This code works properly:

    ...

    <c:forEach items="#{bean.data}" var="var">

              <rich:columns value="#{var.columns}">

                 ...

              </rich:columns>

    </c:forEach>

    ...

Information about sorting and filtering you can find here .

### 6.34.6. Look-and-Feel Customization

For skinnability implementation, the components use a style class redefinition method. Default style classes are mapped on skin parameters.

There are two ways to redefine the appearance of all <rich:columns> components at once:

- Redefine the corresponding skin parameters

- Add to your style sheets style classes used by a <rich:columns> component

### 6.34.7. Skin Parameters Redefinition

Skin parameters redefinition for <rich:columns> are the same as for the <rich:dataTable> component .

### 6.34.8. Definition of Custom Style Classes

Custom style classes for <rich:columns> are the same as for the <rich:dataTable> component .

In order to redefine styles for all <rich:columns> components on a page using CSS, it's enough to create classes with the same names (possible classes could be found in the tables above ) and define necessary properties in them.

Example:

    ...

    .rich-table-subheadercell{

            color: #a0a0a0;

    }

    ...

This is a result:

Figure 6.43. Redefinition styles with predefined classes

In the example column header cells color was changed.

Also it's possible to change styles of particular <rich:columns> component. In this case you should create own style classes and use them in corresponding <rich:columns> styleClass attributes. An example is placed below:

Example:

    ...

    .myClass {

            font-style: oblique;

    }

    ...

The "styleClass" attribute for <rich:columns> is defined as it's shown in the example below:

Example:

    <rich:columns  styleClass="myClass">

This is a result:

Figure 6.44. Redefinition styles with own classes and styleClass attributes

As it could be seen on the picture above, the font style for columns was changed.

### 6.34.9. Relevant Resources Links

Here you can found some additional information for <rich:columns> component usage.

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