1.3

1.2

logic

http://struts.apache.org/tags-logic Note: Some of the features in this taglib are also available in the JavaServer Pages Standard Tag Library (JSTL). The Struts team encourages the use of the standard tags over the Struts specific tags when possible.

This tag library contains tags that are useful in managing conditional generation of output text, looping over object collections for repetitive generation of output text, and application flow management.

For tags that do value comparisons (equal, greaterEqual, greaterThan, lessEqual, lessThan, notEqual), the following rules apply:

The specified value is examined. If it can be converted successfully to a double or a long, it is assumed that the ultimate comparison will be numeric (either floating point or integer). Otherwise, a String comparison will be performed.
The variable to be compared to is retrieved, based on the selector attribute(s) (cookie, header, name, parameter, property) present on this tag. It will be converted to the appropriate type for the comparison, as determined above.
If the specified variable or property returns null, it will be coerced to a zero-length string before the comparison occurs.
The specific comparison for this tag will be performed, and the nested body content of this tag will be evaluated if the comparison returns a true result.

For tags that do substring matching (match, notMatch), the following rules apply:

The specified variable is retrieved, based on the selector attribute(s) (cookie, header, name, parameter, property) present on this tag. The variable is converted to a String, if necessary.
A request time exception will be thrown if the specified variable cannot be retrieved, or has a null value.
The specified value is checked for existence as a substring of the variable, in the position specified by the location attribute, as follows: at the beginning (if location is set to start), at the end (if location is set to end), or anywhere (if location is not specified).

Many of the tags in this tag library will throw a JspException at runtime when they are utilized incorrectly (such as when you specify an invalid combination of tag attributes). JSP allows you to declare an "error page" in the <%@ page %> directive. If you wish to process the actual exception that caused the problem, it is passed to the error page as a request attribute under key org.apache.struts.action.EXCEPTION.

]]> empty

org.apache.struts.taglib.logic.EmptyTag

JSP

Evaluate the nested body content of this tag if the requested variable is either null or an empty string.

This tag evaluates its nested body content only if the specified value is either absent (i.e. null), an empty string (i.e. a java.lang.String with a length of zero), or an empty java.util.Collection or java.util.Map (tested by the .isEmpty() method on the respective interface).

JSTL: The equivalent JSTL tag is <c:if> using the empty operator. For example,
<c:if test="${empty sessionScope.myBean.myProperty}"> do something </c:if>

Since:: Struts 1.1

]]> name false true The variable to be compared is the JSP bean specified by this attribute, if property is not specified, or the value of the specified property of this bean, if property is specified.

]]> property false true The variable to be compared is the property (of the bean specified by the name attribute) specified by this attribute. The property reference can be simple, nested, and/or indexed.

]]> scope false true The bean scope within which to search for the bean named by the name property, or "any scope" if not specified.

]]> equal

org.apache.struts.taglib.logic.EqualTag

JSP

Evaluate the nested body content of this tag if the requested variable is equal to the specified value.

Compares the variable specified by one of the selector attributes against the specified constant value. The nested body content of this tag is evaluated if the variable and value are equal.

]]> cookie false true The variable to be compared is the value of the cookie whose name is specified by this attribute.

]]> header false true The variable to be compared is the value of the header whose name is specified by this attribute. The name match is performed in a case insensitive manner.

]]> parameter false true The variable to be compared is the first, or only, value of the request parameter specified by this attribute.

]]> scope false true The bean scope within which to search for the bean named by the name property, or "any scope" if not specified.

]]> value true true The constant value to which the variable, specified by other attribute(s) of this tag, will be compared.

]]> forward

org.apache.struts.taglib.logic.ForwardTag

empty

Forward control to the page specified by the specified ActionForward entry.

Performs a PageContext.forward() or HttpServletResponse.sendRedirect() call for the global ActionForward entry for the specified name. URL rewriting will occur automatically if a redirect is performed.

]]> name true true The logical name of the global ActionForward entry that identifies the destination, and forwarding approach, to be used. Note: forwarding to Tiles definitions is not supported from this tag. You should forward to them from an Action subclass.

]]> greaterEqual

org.apache.struts.taglib.logic.GreaterEqualTag

JSP

Evaluate the nested body content of this tag if the requested variable is greater than or equal to the specified value.

Compares the variable specified by one of the selector attributes against the specified constant value. The nested body content of this tag is evaluated if the variable is greater than or equal to the value.

]]> cookie false true The variable to be compared is the value of the cookie whose name is specified by this attribute.

]]> header false true The variable to be compared is the value of the header whose name is specified by this attribute. The name match is performed in a case insensitive manner.

]]> parameter false true The variable to be compared is the first, or only, value of the request parameter specified by this attribute.

]]> scope false true The bean scope within which to search for the bean named by the name property, or "any scope" if not specified.

]]> value true true The constant value to which the variable, specified by other attribute(s) of this tag, will be compared.

]]> greaterThan

org.apache.struts.taglib.logic.GreaterThanTag

JSP

Evaluate the nested body content of this tag if the requested variable is greater than the specified value.

Compares the variable specified by one of the selector attributes against the specified constant value. The nested body content of this tag is evaluated if the variable is greater than the value.

]]> cookie false true The variable to be compared is the value of the cookie whose name is specified by this attribute.

]]> header false true The variable to be compared is the value of the header whose name is specified by this attribute. The name match is performed in a case insensitive manner.

]]> parameter false true The variable to be compared is the first, or only, value of the request parameter specified by this attribute.

]]> scope false true The bean scope within which to search for the bean named by the name property, or "any scope" if not specified.

]]> value true true The constant value to which the variable, specified by other attribute(s) of this tag, will be compared.

]]> iterate

org.apache.struts.taglib.logic.IterateTag

org.apache.struts.taglib.logic.IterateTei

JSP

Repeat the nested body content of this tag over a specified collection.

Repeats the nested body content of this tag once for every element of the specified collection, which must be an Iterator, a Collection, a Map (whose values are to be iterated over), or an array. The collection to be iterated over must be specified in one of the following ways:

As a runtime expression specified as the value of the collection attribute.
As a JSP bean specified by the name attribute.
As the property, specified by the property, of the JSP bean specified by the name attribute.

The collection to be iterated over MUST conform to one of the following requirements in order for iteration to be successful:

An array of Java objects or primitives.
An implementation of java.util.Collection, including ArrayList and Vector.
An implementation of java.util.Enumeration.
An implementation of java.util.Iterator.
An implementation of java.util.Map, including HashMap, Hashtable, and TreeMap. NOTE - See below for additional information about accessing Maps.

Normally, each object exposed by the iterate tag is an element of the underlying collection you are iterating over. However, if you iterate over a Map, the exposed object is of type Map.Entry that has two properties:

key - The key under which this item is stored in the underlying Map.
value - The value that corresponds to this key.

So, if you wish to iterate over the values of a Hashtable, you would implement code like the following:


    <logic:iterate id="element" name="myhashtable">

      Next element is <bean:write name="element" property="value"/>

    </logic:iterate>

If the collection you are iterating over can contain null values, the loop will still be performed but no page scope attribute (named by the id attribute) will be created for that loop iteration. You can use the <logic:present> and <logic:notPresent> tags to test for this case.

]]> collection false true java.lang.Object A runtime expression that evaluates to a collection (conforming to the requirements listed above) to be iterated over.

]]> id true false The name of a page scope JSP bean that will contain the current element of the collection on each iteration, if it is not null.

]]> indexId false false The name of a page scope JSP bean that will contain the current index of the collection on each iteration.

]]> length false true The maximum number of entries (from the underlying collection) to be iterated through on this page. This can be either an integer that directly expresses the desired value, or the name of a JSP bean (in any scope) of type java.lang.Integer that defines the desired value. If not present, there will be no limit on the number of iterations performed.

]]> name false true The name of the JSP bean containing the collection to be iterated (if property is not specified), or the JSP bean whose property getter returns the collection to be iterated (if property is specified).

]]> offset false true The zero-relative index of the starting point at which entries from the underlying collection will be iterated through. This can be either an integer that directly expresses the desired value, or the name of a JSP bean (in any scope) of type java.lang.Integer that defines the desired value. If not present, zero is assumed (meaning that the collection will be iterated from the beginning.

]]> property false true Name of the property, of the JSP bean specified by name, whose getter returns the collection to be iterated.

]]> scope false true The bean scope within which to search for the bean named by the name property, or "any scope" if not specified.

]]> type false true Fully qualified Java class name of the element to be exposed through the JSP bean named from the id attribute. If not present, no type conversions will be performed. NOTE: The actual elements of the collection must be assignment-compatible with this class, or a request time ClassCastException will occur.

]]> lessEqual

org.apache.struts.taglib.logic.LessEqualTag

JSP

Evaluate the nested body content of this tag if the requested variable is less than or equal to the specified value.

Compares the variable specified by one of the selector attributes against the specified constant value. The nested body content of this tag is evaluated if the variable is less than or equal to the value.

]]> cookie false true The variable to be compared is the value of the cookie whose name is specified by this attribute.

]]> header false true The variable to be compared is the value of the header whose name is specified by this attribute. The name match is performed in a case insensitive manner.

]]> parameter false true The variable to be compared is the first, or only, value of the request parameter specified by this attribute.

]]> scope false true The bean scope within which to search for the bean named by the name property, or "any scope" if not specified.

]]> value true true The constant value to which the variable, specified by other attribute(s) of this tag, will be compared.

]]> lessThan

org.apache.struts.taglib.logic.LessThanTag

JSP

Evaluate the nested body content of this tag if the requested variable is less than the specified value.

Compares the variable specified by one of the selector attributes against the specified constant value. The nested body content of this tag is evaluated if the variable is less than the value.

]]> cookie false true The variable to be compared is the value of the cookie whose name is specified by this attribute.

]]> header false true The variable to be compared is the value of the header whose name is specified by this attribute. The name match is performed in a case insensitive manner.

]]> parameter false true The variable to be compared is the first, or only, value of the request parameter specified by this attribute.

]]> scope false true The bean scope within which to search for the bean named by the name property, or "any scope" if not specified.

]]> value true true The constant value to which the variable, specified by other attribute(s) of this tag, will be compared.

]]> match

org.apache.struts.taglib.logic.MatchTag

JSP

Evaluate the nested body content of this tag if the specified value is an appropriate substring of the requested variable.

Matches the variable specified by one of the selector attributes (as a String) against the specified constant value. If the value is a substring (appropriately limited by the location attribute), the nested body content of this tag is evaluated.

]]> cookie false true The variable to be matched is the value of the cookie whose name is specified by this attribute.

]]> header false true The variable to be matched is the value of the header whose name is specified by this attribute. The name match is performed in a case insensitive manner.

]]> location false true If not specified, a match between the variable and the value may occur at any position within the variable string. If specified, the match must occur at the specified location (either start or end) of the variable string.

]]> name false true The variable to be matched is the JSP bean specified by this attribute, if property is not specified, or the value of the specified property of this bean, if property is specified.

]]> parameter false true The variable to be matched is the first, or only, value of the request parameter specified by this attribute.

]]> property false true The variable to be matched is the property (of the bean specified by the name attribute) specified by this attribute. The property reference can be simple, nested, and/or indexed.

]]> scope false true The bean scope within which to search for the bean named by the name property, or "any scope" if not specified.

]]> value true true The constant value which is checked for existence as a substring of the specified variable.

]]> messagesNotPresent

org.apache.struts.taglib.logic.MessagesNotPresentTag

JSP

Generate the nested body content of this tag if the specified message is not present in any scope.

Evaluates the nested body content of this tag if an ActionMessages object, ActionErrors object, a String, or a String array is not present in any scope. If such a bean is found, nothing will be rendered.

Since:: Struts 1.1

]]> name false true The parameter key used to retrieve the message from page, request, session or application scope.

]]> property false true Name of the property for which messages should be retrieved. If not specified, all messages (regardless of property) are retrieved.

]]> message false true By default the tag will retrieve the bean it will iterate over from the Globals.ERROR_KEY constant string, but if this attribute is set to 'true' the bean will be retrieved from the Globals.MESSAGE_KEY constant string. Also if this is set to 'true', any value assigned to the name attribute will be ignored.

]]> messagesPresent

org.apache.struts.taglib.logic.MessagesPresentTag

JSP

Generate the nested body content of this tag if the specified message is present in any scope.

Evaluates the nested body content of this tag if an ActionMessages object, ActionErrors object, a String, or a String array is present in any scope. If such a bean is not found, nothing will be rendered.

Since:: Struts 1.1

]]> name false true The parameter key used to retrieve the message from page, request, session, or application scope.

]]> property false true Name of the property for which messages should be retrieved. If not specified, all messages (regardless of property) are retrieved.

]]> notEmpty

org.apache.struts.taglib.logic.NotEmptyTag

JSP

Evaluate the nested body content of this tag if the requested variable is neither null, nor an empty string, nor an empty java.util.Collection (tested by the .isEmpty() method on the java.util.Collection interface).

This tag evaluates its nested body content only if the specified value is present (i.e. not null) and is not an empty string (i.e. a java.lang.String with a length of zero).

JSTL: The equivalent JSTL tag is <c:if> using the ! empty operator. For example,
<c:if test="${ ! empty sessionScope.myBean.myProperty}"> do something </c:if>

]]> scope false true The bean scope within which to search for the bean named by the name property, or "any scope" if not specified.

]]> notEqual

org.apache.struts.taglib.logic.NotEqualTag

JSP

Evaluate the nested body content of this tag if the requested variable is not equal to the specified value.

Compares the variable specified by one of the selector attributes against the specified constant value. The nested body content of this tag is evaluated if the variable and value are not equal.

]]> cookie false true The variable to be compared is the value of the cookie whose name is specified by this attribute.

]]> header false true The variable to be compared is the value of the header whose name is specified by this attribute. The name match is performed in a case insensitive manner.

]]> parameter false true The variable to be compared is the first, or only, value of the request parameter specified by this attribute.

]]> scope false true The bean scope within which to search for the bean named by the name property, or "any scope" if not specified.

]]> value true true The constant value to which the variable, specified by other attribute(s) of this tag, will be compared.

]]> notMatch

org.apache.struts.taglib.logic.NotMatchTag

JSP

Evaluate the nested body content of this tag if the specified value is not an appropriate substring of the requested variable.

Matches the variable specified by one of the selector attributes (as a String) against the specified constant value. If the value is not a substring (appropriately limited by the location attribute), the nested body content of this tag is evaluated.

]]> cookie false true The variable to be matched is the value of the cookie whose name is specified by this attribute.

]]> header false true The variable to be matched is the value of the header whose name is specified by this attribute. The name match is performed in a case insensitive manner.

]]> parameter false true The variable to be matched is the first, or only, value of the request parameter specified by this attribute.

]]> scope false true The bean scope within which to search for the bean named by the name property, or "any scope" if not specified.

]]> value true true The constant value which is checked for existence as a substring of the specified variable.

]]> notPresent

org.apache.struts.taglib.logic.NotPresentTag

JSP

Generate the nested body content of this tag if the specified value is not present in this request.

Depending on which attribute is specified, this tag checks the current request, and evaluates the nested body content of this tag only if the specified value is not present. Only one of the attributes may be used in one occurrence of this tag, unless you use the property attribute, in which case the name attribute is also required.

]]> cookie false true Checks for the existence of a cookie with the specified name.

]]> header false true Checks for the existence of an HTTP header with the specified name. The name match is performed in a case insensitive manner.

]]> name false true Checks for the existence of a JSP bean, in any scope, with the specified name. If property is also specified, checks for a non-null property value for the specified property.

]]> parameter false true Checks for the existence of at least one occurrence of the specified request parameter on this request, even if the parameter value is a zero-length string.

]]> property false true Checks for the existence of a non-null property value, returned by a property getter method on the JSP bean (in any scope) that is specified by the name attribute. Property references can be simple, nested, and/or indexed.

]]> role false true Checks whether the currently authenticated user (if any) has been associated with the specified security role.

]]> scope false true The bean scope within which to search for the bean named by the name property, or "any scope" if not specified.

]]> user false true Checks whether the currently authenticated user principal has the specified name.

]]> present

org.apache.struts.taglib.logic.PresentTag

JSP

Generate the nested body content of this tag if the specified value is present in this request.

Depending on which attribute is specified, this tag checks the current request, and evaluates the nested body content of this tag only if the specified value is present. Only one of the attributes may be used in one occurrence of this tag, unless you use the property attribute, in which case the name attribute is also required.

]]> cookie false true Checks for the existence of a cookie with the specified name.

]]> header false true Checks for the existence of an HTTP header with the specified name. The name match is performed in a case insensitive manner.

]]> name false true Checks for the existence of a JSP bean, in any scope, with the specified name. If property is also specified, checks for a non-null property value for the specified property.

]]> parameter false true Checks for the existence of at least one occurrence of the specified request parameter on this request, even if the parameter value is a zero-length string.

]]> role false true Checks whether the currently authenticated user (if any) has been associated with any of the specified security roles. Use a comma-delimited list to check for multiple roles. Example:

<logic:present role="role1,role2,role3">
                code.....
            </logic:present>

]]> scope false true The bean scope within which to search for the bean named by the name property, or "any scope" if not specified.

]]> user false true Checks whether the currently authenticated user principal has the specified name.

]]> redirect

org.apache.struts.taglib.logic.RedirectTag

Render an HTTP Redirect

Performs an HttpServletResponse.sendRedirect() call to the hyperlink specified by the attributes to this tag. URL rewriting will be applied automatically, to maintain session state in the absence of cookies.

The base URL for this redirect is calculated based on which of the following attributes you specify (you must specify exactly one of them):

forward - Use the value of this attribute as the name of a global ActionForward to be looked up, and use the module-relative or context-relative URI found there.
href - Use the value of this attribute unchanged.
page - Use the value of this attribute as an module-relative URI, and generate a server-relative URI by including the context path.

Normally, the redirect you specify with one of the attributes described in the previous paragraph will be left unchanged (other than URL rewriting if necessary). However, there are two ways you can append one or more dynamically defined query parameters to the hyperlink -- specify a single parameter with the paramId attribute (and its associated attributes to select the value), or specify the name (and optional property) attributes to select a java.util.Map bean that contains one or more parameter ids and corresponding values.

To specify a single parameter, use the paramId attribute to define the name of the request parameter to be submitted. To specify the corresponding value, use one of the following approaches:

Specify only the paramName attribute - The named JSP bean (optionally scoped by the value of the paramScope attribute) must identify a value that can be converted to a String.
Specify both the paramName and paramProperty attributes - The specified property getter method will be called on the JSP bean identified by the paramName (and optional paramScope) attributes, in order to select a value that can be converted to a String.

If you prefer to specify a java.util.Map that contains all of the request parameters to be added to the hyperlink, use one of the following techniques:

Specify only the name attribute - The named JSP bean (optionally scoped by the value of the scope attribute) must identify a java.util.Map containing the parameters.
Specify both name and property attributes - The specified property getter method will be called on the bean identified by the name (and optional scope) attributes, in order to return the java.util.Map containing the parameters.

As the Map is processed, the keys are assumed to be the names of query parameters to be appended to the hyperlink. The value associated with each key must be either a String or a String array representing the parameter value(s). If a String array is specified, more than one value for the same query parameter name will be created.

]]> action false true Logical name of a global Action that contains the actual content-relative URI of the destination of this transfer. This hyperlink may be dynamically modified by the inclusion of query parameters, as described in the tag description. You must specify exactly one of the action attribute, the forward attribute, the href attribute, or the page attribute.

]]> anchor false true Optional anchor tag ("#xxx") to be added to the generated hyperlink. Specify this value without any "#" character.

]]> forward false true Logical name of a global ActionForward that contains the actual content-relative URI of the destination of this redirect. This URI may be dynamically modified by the inclusion of query parameters, as described in the tag description. You must specify exactly one of the forward attribute, the href attribute, the linkName attribute, or the page attribute.

]]> href false true The URL to which this redirect will transfer control. This URL may be dynamically modified by the inclusion of query parameters, as described in the tag description. You must specify exactly one of the forward attribute, the href attribute, the linkName attribute, or the page attribute.

]]> name false true The name of a JSP bean that contains a Map representing the query parameters (if property is not specified), or a JSP bean whose property getter is called to return a Map (if property is specified).

]]> page false true The context-relative path (beginning with a "/" character) to which this hyperlink will transfer control if activated. This hyperlink may be dynamically modified by the inclusion of query parameters, as described in the tag description. You must specify exactly one of the forward attribute, the href attribute, the linkName attribute, or the page attribute.

]]> paramId false true The name of the request parameter that will be dynamically added to the generated hyperlink. The corresponding value is defined by the paramName and (optional) paramProperty attributes, optionally scoped by the paramScope attribute

]]> paramName false true The name of a JSP bean that is a String containing the value for the request parameter named by paramId (if paramProperty is not specified), or a JSP bean whose property getter is called to return a String (if paramProperty is specified). The JSP bean is constrained to the bean scope specified by the paramScope property, if it is specified.

]]> paramProperty false true The name of a property of the bean specified by the paramName attribute, whose return value must be a String containing the value of the request parameter (named by the paramId attribute) that will be dynamically added to this hyperlink.

]]> paramScope false true The scope within which to search for the bean specified by the paramName attribute. If not specified, all scopes are searched.

]]> property false true The name of a property of the bean specified by the name attribute, whose return value must be a java.util.Map containing the query parameters to be added to the hyperlink. You must specify the name attribute if you specify this attribute.

]]> scope false true The scope within which to search for the bean specified by the name attribute. If not specified, all scopes are searched.

]]> transaction false true boolean Set to true if you want the current transaction control token included in the generated URL for this redirect.

]]> useLocalEncoding false true boolean If set to true, LocalCharacterEncoding will be used, that is, the characterEncoding set to the HttpServletResponse, as prefered character encoding rather than UTF-8, when URLEncoding is done on parameters of the URL.

]]>