Class AbstractFormTag

java.lang.Object

jakarta.servlet.jsp.tagext.TagSupport

org.springframework.web.servlet.tags.RequestContextAwareTag

org.springframework.web.servlet.tags.HtmlEscapingAwareTag

org.springframework.web.servlet.tags.form.AbstractFormTag

All Implemented Interfaces:

jakarta.servlet.jsp.tagext.IterationTag, jakarta.servlet.jsp.tagext.JspTag, jakarta.servlet.jsp.tagext.Tag, jakarta.servlet.jsp.tagext.TryCatchFinally, Serializable

Direct Known Subclasses:

AbstractDataBoundFormElementTag

public abstract class AbstractFormTag
extends HtmlEscapingAwareTag

Base class for all JSP form tags. Provides utility methods for null-safe EL evaluation and for accessing and working with a TagWriter.

Subclasses should implement the writeTagContent(TagWriter) to perform actual tag rendering.

Subclasses (or test classes) can override the createTagWriter() method to redirect output to a Writer other than the JspWriter associated with the current PageContext.

Since:

2.0

Author:

Rob Harrop, Juergen Hoeller

See Also:

• Serialized Form

Field Summary

Fields inherited from class RequestContextAwareTag

logger, REQUEST_CONTEXT_PAGE_ATTRIBUTE

Fields inherited from class jakarta.servlet.jsp.tagext.TagSupport

id, pageContext

Fields inherited from interface jakarta.servlet.jsp.tagext.IterationTag

EVAL_BODY_AGAIN

Fields inherited from interface jakarta.servlet.jsp.tagext.Tag

EVAL_BODY_INCLUDE, EVAL_PAGE, SKIP_BODY, SKIP_PAGE

Constructor Summary

Constructors

Constructor	Description
AbstractFormTag()

Method Summary

Modifier and Type	Method	Description
protected TagWriter	createTagWriter()	Create the TagWriter which all output will be written to.
protected final int	doStartTagInternal()	Provide a simple template method that calls createTagWriter() and passes the created TagWriter to the writeTagContent(TagWriter) method.
protected @Nullable Object	evaluate(String attributeName, @Nullable Object value)	Evaluate the supplied value for the supplied attribute name.
protected String	getDisplayString(@Nullable Object value)	Get the display value of the supplied Object, HTML escaped as required.
protected String	getDisplayString(@Nullable Object value, @Nullable PropertyEditor propertyEditor)	Get the display value of the supplied Object, HTML escaped as required.
protected boolean	isDefaultHtmlEscape()	Overridden to default to true in case of no explicit default given.
protected final void	writeOptionalAttribute(TagWriter tagWriter, String attributeName, @Nullable String value)	Optionally writes the supplied value under the supplied attribute name into the supplied TagWriter.
protected abstract int	writeTagContent(TagWriter tagWriter)	Subclasses should implement this method to perform tag content rendering.

Methods inherited from class HtmlEscapingAwareTag

htmlEscape, isHtmlEscape, isResponseEncodedHtmlEscape, setHtmlEscape

Methods inherited from class RequestContextAwareTag

doCatch, doFinally, doStartTag, getRequestContext

Methods inherited from class jakarta.servlet.jsp.tagext.TagSupport

doAfterBody, doEndTag, findAncestorWithClass, getId, getParent, getValue, getValues, release, removeValue, setId, setPageContext, setParent, setValue

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

AbstractFormTag

public AbstractFormTag()

Method Details

evaluate

protected @Nullable Object evaluate(String attributeName,
 @Nullable Object value)
                             throws jakarta.servlet.jsp.JspException

Evaluate the supplied value for the supplied attribute name.

The default implementation simply returns the given value as-is.

Throws:

jakarta.servlet.jsp.JspException

writeOptionalAttribute

protected final void writeOptionalAttribute(TagWriter tagWriter,
 String attributeName,
 @Nullable String value)
                                     throws jakarta.servlet.jsp.JspException

Optionally writes the supplied value under the supplied attribute name into the supplied TagWriter. In this case, the supplied value is evaluated first and then the String representation is written as the attribute value. If the resultant String representation is null or empty, no attribute is written.

Throws:

jakarta.servlet.jsp.JspException

See Also:

• TagWriter.writeOptionalAttributeValue(String, String)

createTagWriter

protected TagWriter createTagWriter()

Create the TagWriter which all output will be written to. By default, the TagWriter writes its output to the JspWriter for the current PageContext. Subclasses may choose to change the Writer to which output is actually written.

doStartTagInternal

protected final int doStartTagInternal()
                                throws Exception

Provide a simple template method that calls createTagWriter() and passes the created TagWriter to the writeTagContent(TagWriter) method.

Specified by:

doStartTagInternal in class RequestContextAwareTag

Returns:

the value returned by writeTagContent(TagWriter)

Throws:

Exception - any exception, any checked one other than a JspException gets wrapped in a JspException by doStartTag

See Also:

• TagSupport.doStartTag()

getDisplayString

protected String getDisplayString(@Nullable Object value)

Get the display value of the supplied Object, HTML escaped as required. This version is not PropertyEditor-aware.

getDisplayString

protected String getDisplayString(@Nullable Object value,
 @Nullable PropertyEditor propertyEditor)

Get the display value of the supplied Object, HTML escaped as required. If the supplied value is not a String and the supplied PropertyEditor is not null then the PropertyEditor is used to obtain the display value.

isDefaultHtmlEscape

protected boolean isDefaultHtmlEscape()

Overridden to default to true in case of no explicit default given.

Overrides:

isDefaultHtmlEscape in class HtmlEscapingAwareTag

See Also:

• RequestContextAwareTag.getRequestContext()

writeTagContent

protected abstract int writeTagContent(TagWriter tagWriter)
                                throws jakarta.servlet.jsp.JspException

Subclasses should implement this method to perform tag content rendering.

Returns:

valid tag render instruction as per Tag.doStartTag().

Throws:

jakarta.servlet.jsp.JspException