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JSTL Reference Sheet | Wendy's Corner

JSTL Reference Sheet

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There are five types of JSTL tag Library:

  • Core Tags

  • Formatting Tags

  • SQL Tags

  • JSTL Functions

  • XML Tags (I skip this part)

Before you use JSTL library, you need to download it and put it to webapps\ROOT\WEB-INF\lib directoy.

Core Tages

Make sure you include core tag library in your JSP file: <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

Following tags are common core tags with an explaination of their usage:

<c:out>: Display the result of an expression. Similar to <%= %> exception you use a . notation to access property now.

Example: <c:out value="person.age"/>

<c:set>: Evaluates an expression and uses the result to set a value of a JavaBean or a java.util.Map object.

Example: <c:set var="var_name" value="${person.age}"/>

<c:remove>: Remove a variable from either a specified scope or the first scope where the variable is found.

Example: <c:remove var="var_name"/>

<c:catch>: Catches any throwable error and optionally expost it.

You can combine it with

<c:catch var="exception">
<p>${person.age}</p>
</c:catch>

<c:if test="${exception!=null}">
    <p>The exception is: ${exception}</p>
</c:if>

<c:if>:Display content only if test is passed. <c:choose> ,<c:when> ,c:otherwise> ususally are used together to create (nested) if-else loop

Example: <c:if test="${person.age>20}">Hello World!</c:if>

<c:choose>
    <c:when test="${person.age>18}">
        Adult
    </c:when>
    <c:when test="${12<person.age<18}">
        Junior
    </c:when>
    <c:otherwise>
        Child
    </c:otherwise>
</c:choose>

<c:import>: Work like <include>, takes an url and allows for inclusion of content from a differenet website or an FTP server.

Example: <c:import var="var_name" url="http://pengyin-shan.com"/> fetches complete content from this website and would store in variable data.

<c:forEach>: Iterates over a collection of objects. Work like for, while or do-while in Java. Possiable Parameters:

  • begin: Element to start with. 0 means the first item

  • end: Element to end with. 0 means the first item

  • step: Process every step items. Default is 1.

  • var: Name of variable for current item

  • varStatus: Name of variable for current loop status. Works like i or count in java.

Example:

<c:forEach items="${people}" var="person" varStatus="theCount">
${theCount.index}
</c:forEach>

Note: {varStatus.index} starts from 0. {varStatus.count} starts from 1.

<c:forTokens>: Similar as <c:forEach>. It is used to break a string into tokens and iterate through each of the tokens. Requested Parameter: delims, define character that is used for division.

<c:url> formats a URL string and optionally put to a variable and print to page

<c:param> allows proper URL request parameter to be specified with URL. Usually work with <c:url>

<c:redirect> automatically re-direct page to another URL

Example: <c:forTokens items="a,b,c" delims="," var="charName">${charName}</c:forTokens>

<c:url var="testUrl" value="/index.jsp">
    <c:param name="id" value="1234"/>
</c:url>
#now testUrl is: /index.jsp?id=1234
<a href="<c:url value=${testUrl}">Test</a>
<c:redirect url="${testUrl}"/>

Formatting Tags

Make sure you include formatting tag library in your JSP file: <%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %>

Following tags are common formatting tags with an explaination of their usage:

<fmt:formatNumber>: format numbers, percentages and currencies. It has lots of parameters for configuration. You can view here for detail.

Example: <p>Number is: <fmt:formatNumber value="${balance}" maxIntegerDigits="3" maxFactionDigits="3" pattern="###.###E0"></p>

<fmt:formatDate>: Similarly but just for date. For example, you can set timezone using this tag. You can view detail here.

<fmt:parseNumber>: parse numbers, percentages and currencies. You are given a number and this tag can parse number to certain format. You can view here for useful parameters.

Example: <fmt:parseNumber var="i" type="number" value="${balance}" integerOnly="true"/>

<fmt:parseDate>:Similary, but just for Date. For example, you can set date as "YYYY-MM-DD" format. You can view detail here.

<fmt:message> tag maps key to localized message

<fmt:bundle> often being used with <fmt:message>. It will find a java class which extend ListResourceBunder, and use it for message

<fmt:setBundle> is similar to <fmt:bundle> except it not wraps <fmt:message>

public class Example extends ListResouceBundle{
    public Object[][] getContents(){
        return contents;
    }
    static final Object[][] contents = {
        {"count.one","One"},
        {"count.two","Two"}
    }
}

:::html
<fmt:bundle basedname="com.pengyinshan.Example">
    <fmt:message key="count.one"/>
    <fmt:message key="count.two"/>
        #if you use <fmt:setBundle>, <fmt:message> will be outside
</fmt:bundle>

<fmt:setLocale> is similar as <fmt:setBundle>. You need to specify class Name. Tag will find the scale that corresponds to this name <fmt:requestCoding> set up encoding. You don't need extra class for it

Assume we have same example:

publc class Exmple_en_us extends ListResourceBundle{
    //...
}

:::html
<fmt:requestEncoding value="en_us"/>
<fmt:setLocale value="en_us"/>
<fmt:bundle basedname="com.pengyinshan.Example">
</fmt:bundle>

<fmt:timeZone> and <fmt:setTimeZone> are used to specify timezone in body.

They are oftern used above <fmt:formatDate>

<fmt:setTimeZone value="EST">
    <fmt:formatDate value="${now}" timeStyle="long" dateStyle="long" type="both" />
</fmt:setTimeZone>

SQL Tags

Make sure you include sql tag library in your JSP file: <%@ taglib prefix="sql" uri="http://java.sun.com/jsp/jstl/sql" %>

Following tags are common sql tags with an explaination of their usage:

<sql:setDateSource>: Takes several parameters and set data source.

For example: <sql:setDataSource var="snapshot" driver="com.mysql.jdbc.Driver" url="jdbc:mysql://localhost/TEST" user="user_id"password="mypassword"/>

<sql:query>: Take several parameters and run a query. You can put result to a variable and use it as var.id, var.last, var.name, etc. You may want to use <c:forEach> for result.

For example:

<sql:query dataSource="${snapshot}" var="result">
SELECT * from Employees;
</sql:query>

<sql:udpate>: Use for sql query that does not return value, such as insert, update or delete.

For example:

<sql:update dataSource="${snapshot}" var="count">
   INSERT INTO Employees VALUES (104, 2, 'Nuha', 'Ali');
</sql:update>

<sql:param>: Use for fill parameter to <sql:update> or <sql:query> if need.

<sql:dateParam>: Similaly but specailly used to modify date/timestamp.

The sequence of tags corresponding to sequnce of ? in query.

For example:

<sql:update dataSource="${snapshot}" var="count">
  Update Employees Set Dob = ? WHERE Id = ?
  <sql:dateParam value="<%=DoB%>" type="DATE" />
  <sql:param value="${empId}" />
</sql:update>

<sql:transaction>: Wrap some <sql:update> and <sql:query> to create transaction.

For Example:

<sql:transaction dataSource="${snapshot}">
#<sql:update>....
</sql:transaction>

JSTL Functions

Make sure you include function tag library in your JSP file: <%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>

Normally JSTL functions are used within ${}.

Following tags are common function tags with an explaination of their usage:

<fn:contains>: Equals to boolean contains(java.lang.String, java.lang.String).

<fn:containsIgnoreCase>: Similar but just ignore case problem.

Example:

<c:if test="${fn:contains(var_name,'test')}">
<p>Found "test" in variable</p>
</c:if>

<fn:endsWith>: Determines whether an input string ends with a specified suffix. Equals to boolean endsWith(java.lang.String, java.lang.String).

<fn:startWith>: Similar but it work with prefix.

Example:

<c:if test="${fn:endsWith(var_name, '123')}">
   <p>String ends with 123<p>
</c:if>

<fn:indexOf>: Returns the index within a string of a specified substring. Equals to int indexOf(java.lang.String, java.lang.String).

<fn:length>: Returns the length of a string. Equals to int length(java.lang.Object).

<fn:split>: splits a string into an array of substrings. Equals to java.lang.String[] split(java.lang.String, java.lang.String).

<fn:join>: Concatenates all the elements of an array into a string with a specified separator. Equals to String join (java.lang.String[], java.lang.String).

<fn:replace>: replace all occurrences of a string with another string.

Example:

<c:set var="string1" value="This is first String."/>
<c:set var="string2" value="${fn:split(string1, ' ')}" />
<c:set var="string3" value="${fn:join(string2, '-')}" />
<c:set var="string4" value="${fn:replace(string3, '-' , '+')}" />

<fn:substring>: Returns a subset of a string specified by start and end index. Equals to java.lang.String substring(java.lang.String, int, int).

<fn:substringAfter>: Returns the part of a string after a specified substring. Example: <c:set var="string2" value="${fn:substringAfter(string1, 'is')}" />. Note is here is included in result.

<fn:substringBefore>: Returns the part of a string before a specified substring. Example is similar as above. Note is here is excluded in result.

<fn:toLowerCase> and <fn:toUpperCase>:take a string and transfer its case. For example: <c:set var="string2" value="${fn:toLowerCase(string1)}" />.

<fn:trim>: Removes white space from both ends of a string. Example: <c:set var="string1" value="This is first String "/>.

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