JSTL标签库

JSTL

• apache对EL表达式的扩展
• jstl.jar包
  • core 核心库
  • fmt 格式化标签库

---

Core (c标签)

• out && set

  • <c:out value="xx"/>
  • <c:out value="${xxx}"/> // ${xxx}
  • <c:out value="${xxx}" default="xxx" escapeXml="true"/> // 默认true

  ---

  • <c:set var="name" value="value"/>
  • <c:set var="name" value="value" scope="session"/> // scope默认pageContext

• remove

  • <c:remove var="name"/> //所有域的变量
  • <c:remove var="name" scope="session"/>

• url (路径前面自动加上项目名)

  • <c:url value="/index.jsp"/> //必须以斜杠开头
  • 子标签 <c:param/> url后面添加参数
    • <c:param name="name" value="value"/> // value会有url编码

• if

  • <c:if test="${not empty a}">
    <c:out value="${a}"/>
    </c:if>

• choose

  • <c:choose>
    <c:when test="boolean" ></c:when>
    <c:when test="boolean"></c:when>
    <c:otherwise></c:otherwise>
    </c:choose>

• forEach

  • <c:forEach var="i" begin="1" end="10" step="2">
    </c:forEach>
  • <c:forEach items="${list}" var="item">
    ${item}
    </c:forEach>

• 循环状态

• <c:forEach items="${list}" item="ele" varStatus="vs">
  ${vs.index} ${vs.count} ${vs.first} ${vs.last}
  </c:forEach>

---

fmt (格式化标签)

• <fmt:formatDate value="${date}" pattern="yyyy-MM-dd HH:mm:ss" />
• <fmt:formatNumber value="${number}" pattern="#.###" />

---

SimpleTag || SimpleTagSurport

• void doTag() //每次执行
• void setJspBody(JspFragment jspBody)
• void setJspContext(JspContext context)
• JspTag getParent() //设置标签体
• void setParent(JspTag parent)

eg:

package com.suse.yuxin.tags;
import java.io.IOException;
import javax.servlet.jsp.JspContext;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.JspFragment;
import javax.servlet.jsp.tagext.JspTag;
import javax.servlet.jsp.tagext.SimpleTag;
   
public class TestSimpleTag implements SimpleTag {
    @Override
    public void doTag() throws JspException, IOException {
      context.getOut().write("Hello tags");
    }

    @Override
    public JspTag getParent() {
        return parent;
    }

    @Override
    public void setJspBody(JspFragment jspBody) {
        this.fragment = jspBody;
    }
    
    
    private JspTag parent;
    private JspContext context;
    
    private JspFragment fragment;
    
    
    @Override
    public void setJspContext(JspContext pc) {
        this.context = pc;
    }

    @Override
    public void setParent(JspTag parent) {
        this.parent = parent;
    }
}

<taglib xmlns="http://java.sun.com/xml/ns/j2ee"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
  version="2.0">
 <tlib-version>1.0</tlib-version>
 <short-name>hellotag</short-name>
 <uri>http://www.suse.yuxin/tags/1.0</uri>
 
 <tag>
    <name>hellotag</name>
    <tag-class>com.suse.yuxin.tags.TestSimpleTag</tag-class>
    <body-content>empty</body-content>
 </tag>
 
</taglib>

<%@ taglib prefix="mm" uri="/WEB-INF/tlds/hellotag.tld" %>
<mm:hellotag/>

标签体内容

• empty
• scriptless 只能是EL表达式 或者其他标签 // <tag>${el}</tag>

标签的属性

• 标签处理类至少要有一个set方法
• 在tld里面配置属性

   <tag>
    <name>hellotag</name>
    <tag-class>com.suse.yuxin.tags.TestSimpleTag</tag-class>
    <body-content>empty</body-content>
    <attribute>
        <name>test</name>
        <required>false</required>
        <rtexprvalue>true</rtexprvalue> <!-- 指定属性是否使用EL -->
    </attribute>
  

</tag>

- - -

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# :)