# com.bea.wlw.netui.tags.databinding.grid.column
ExpressionColumn Class

public class ExpressionColumn
extends `FormattableColumn`

A column that can use expressions in addition to formatters to format the value of a data cell. The expression column enables combining data from different fields of the current data item or even from different expression contexts into a value for the cell. An expression column is not sortable or filterable.

Attribute Descriptions
Attribute | Required | Runtime Expression Evaluation | Data Bindable
--- | --- | --- | ---
title | No | No | No
The text that will be rendered in the header for this column.
value | No | No | Yes
The expression value that can contain expressions that reference data in the current data item. The result of the expression evaluation will be rendered in the data cell.

Related Topics

Grid

Hierarchy
  `Object`
  `TagSupport`
  `BodyTagSupport`
  `AbstractBaseTag`
  `StructuredBaseTag`
  `GridComponent`
  `GridColumn`
  `FormattableColumn`
  `ExpressionColumn`

All Implemented Interfaces
  `BodyTag`, `Formattable`, `IterationTag`, `Serializable`, `Tag`

## Field Summary

Fields from com.bea.wlw.netui.tags.databinding.base`.`StructuredBaseTag``
`EMPTY_STRING`

Fields from com.bea.wlw.netui.tags`.`AbstractBaseTag``
``ATTR_GENERAL`, `ATTR_GENERAL_EXPRESSION`, `ATTR_JAVASCRIPT`, `ATTR_STYLE`, `CLASS`, `ID`, `JAVASCRIPT_STATUS`, `NAME`, `NETUI_UNIQUE_CNT`, `ONCLICK`, `ONDBLCLICK`, `ONKEYDOWN`, `ONKEYPRESS`, `ONKEYUP`, `ONMOUSEDOWN`, `ONMOUSEMOVE`, `ONMOUSEOUT`, `ONMOUSEOVER`, `ONMOUSEUP`, `STYLE`, `TABINDEX``

Fields from javax.servlet.jsp.tagext`.`BodyTagSupport``
`bodyContent`

Fields from javax.servlet.jsp.tagext`.`TagSupport``
`id, pageContext`

Fields from interface javax.servlet.jsp.tagext`.`BodyTag``
`EVAL_BODY_BUFFERED, EVAL_BODY_TAG`

Fields from interface javax.servlet.jsp.tagext`.`IterationTag``
`EVAL_BODY_AGAIN`

Fields from interface javax.servlet.jsp.tagext`.`Tag``
`EVAL_BODY_INCLUDE, EVAL_PAGE, SKIP_BODY, SKIP_PAGE`

## Constructor Summary

ExpressionColumn()

## Method Summary

`public `String`` | `getTagName`() Get the name of this tag.
`public `String`` | `getTitle`() Get the title rendered in the header cell of this column.
`public `String`` | `getValue`() Get the value of this tag.
`protected void` | `localRelease`() Reset all of the fields of this tag.
`public `String`` | `renderDataCell`() Render a cell for the "current" data item.
`public `String`` | `renderFooterCell`() Render the footer.
`public `String`` | `renderHeaderCell`() Render the header cell for this column.
`public void` | `setTitle`(`String` title) Set the title rendered in the header cell of this column.
`public void` | `setValue`(`String` value) Set the value of this tag.

Methods from `com.bea.wlw.netui.tags.databinding.grid.column.`FormattableColumn``
``addFormatter`, `format`, `renderStartTag``

Methods from `com.bea.wlw.netui.tags.databinding.grid.column.`GridColumn``
``getColumns`, `getStyleClassPrefix`, `getValidContainerType`, `localRelease`, `prepare`, `renderCloseCellTag`, `renderDataCellTag`, `renderEndTag`, `renderFooterCellTag`, `renderHeaderCellTag`, `renderOpenCellTag`, `renderStartTag`, `setStyleClassPrefix``

Methods from `com.bea.wlw.netui.tags.databinding.grid.`GridComponent``
``getCurrentRenderState`, `getGrid`, `getGridContext`, `getValidContainerType`, `localRelease`, `prepare``

Methods from `com.bea.wlw.netui.tags.databinding.base.`StructuredBaseTag``
`addContent, doEndTag, doStartTag, getContent, getCurrentRenderState, getValidContainerType, localRelease, prepare, renderEndTag, renderStartTag, verifyAttributes, verifyStructure`

Methods from `com.bea.wlw.netui.tags.`AbstractBaseTag``
``addTagIdMapping`, `evaluateAttributeToString`, `filter`, `filter`, `getJavaScriptUtils`, `getNearestForm`, `getScriptReporter`, `getUserLocale`, `localRelease`, `registerTagError`, `release`, `renderAttribute`, `rewriteName`, `write``

Methods from `javax.servlet.jsp.tagext.`BodyTagSupport``
`doAfterBody, doEndTag, doInitBody, doStartTag, getBodyContent, getPreviousOut, release, setBodyContent`

Methods from `javax.servlet.jsp.tagext.`TagSupport``
`doAfterBody, doEndTag, doStartTag, findAncestorWithClass, getId, getParent, getValue, getValues, release, removeValue, setId, setPageContext, setParent, setValue`

Methods from class `java.lang.`Object``
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Methods from interface `javax.servlet.jsp.tagext.`BodyTag``
`doInitBody, setBodyContent`

Methods from interface `com.bea.wlw.netui.tags.html.`Formattable``
``addFormatter``

Methods from interface `javax.servlet.jsp.tagext.`IterationTag``
`doAfterBody`

Methods from interface `javax.servlet.jsp.tagext.`Tag``
`doEndTag, doStartTag, getParent, release, setPageContext, setParent`

## Constructor Detail

### ExpressionColumn

    public ExpressionColumn()

## Method Detail

### getTagName() Method

    public String getTagName()

Get the name of this tag. This is used to identify the type of this tag for reporting tag errors.

Overrides
  `AbstractBaseTag.getTagName()`

#### Returns

a constant String representing the name of this tag.

### getTitle() Method

    public String getTitle()

Get the title rendered in the header cell of this column.

#### Returns

the title of the colum

### getValue() Method

    public String getValue()

Get the value of this tag.

#### Returns

the value of this tag

### localRelease() Method

    protected void localRelease()

Reset all of the fields of this tag.

Overrides
  `FormattableColumn.localRelease()`

### renderDataCell() Method

    public String renderDataCell()
         throws JspException

Render a cell for the "current" data item. The value attribute is first evaluated as an expression, then formatted using any contained Formatter tags, and is finally returned to be buffered. If errors occur during the process of expression evaluation on the value attribute, these errors are reported in the page.

Overrides
  `GridColumn.renderDataCell()`

#### Returns

the String content that should be buffered for this tag

#### Exceptions

``JspException``
  if an error occurs that can not be reported in the page

### renderFooterCell() Method

    public String renderFooterCell()

Render the footer. This footer contains no text.

Overrides
  `GridColumn.renderFooterCell()`

#### Returns

the emtpy string

### renderHeaderCell() Method

    public String renderHeaderCell()

Render the header cell for this column. The title attribute is rendered in the header of an ExpressionColumn.

Overrides
  `GridColumn.renderHeaderCell()`

#### Returns

the String content that should be buffered for this tag

### setTitle(String) Method

    public void setTitle(String title)

Set the title rendered in the header cell of this column.

#### Parameters

title
  the title of the column

### setValue(String) Method

    public void setValue(String value)

Set the value of this tag. The value may contain an expression(s) that will be evaluated before the data for each item in the Grid's data set is rendered. The databinding expression `container` may be used to access the "current" data item that is being rendered. For example, the expression `container.item` accesses the current data item.

#### Parameters

value
  the value of this tag. This attribute may contain expression(s).