jstl自定义函数的使用

由于本人之前并没有接触过jstl标签，说来也可笑，之前一直使用struts2标签。最近项目用到jstl，所以做些记录方便以后自己查看。

jstl的强大原因之一我认为就是他的自定义函数，我们可以在前端页面直接就调用了java后台的一些常用方法，这一点真是让我爱不释手好吗。废话不多说，接下来具体看看如何使用jstl的自定义函数。

首先jstl的jar包肯定是要导的，在这就不啰嗦了。

使用jstl自定义函数要做到以下几点：

1.定义的方法必须是public的并且是static的；

2.定义相应的tld文件在WEB-INF目录或其子目录下；

3.定义相应的自定义函数库<%@ taglib prefix="fns" uri="/WEB-INF/tlds/fns.tld" %>。

具体示例代码如下：

fns.tld文件

<?xml version="1.0" encoding="UTF-8" ?>

<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">
    
  <description>JSTL 1.1 functions library</description>
  <display-name>JSTL functions sys</display-name>
  <tlib-version>1.1</tlib-version>
  <short-name>fns</short-name>
  <uri>http://java.sun.com/jsp/jstl/functionss</uri>

  <function>
    <description>获取管理路径</description>
    <name>getAdminPath</name>
    <function-class>com.gisquest.djgx.common.config.Global</function-class>
    <function-signature>java.lang.String getAdminPath()</function-signature>
    <example>${fns:getAdminPath()}</example>
  </function>
  <function>
    <description>获取网站路径</description>
    <name>getFrontPath</name>
    <function-class>com.gisquest.djgx.common.config.Global</function-class>
    <function-signature>java.lang.String getFrontPath()</function-signature>
    <example>${fns:getFrontPath()}</example>
  </function>
  <function>
    <description>获取网站URL后缀</description>
    <name>getUrlSuffix</name>
    <function-class>com.gisquest.djgx.common.config.Global</function-class>
    <function-signature>java.lang.String getUrlSuffix()</function-signature>
    <example>${fns:getUrlSuffix()}</example>
  </function>
  <function>
    <description>获取配置</description>
    <name>getConfig</name>
    <function-class>com.gisquest.djgx.common.config.Global</function-class>
    <function-signature>java.lang.String getConfig(java.lang.String)</function-signature>
    <example>${fns:getConfig(key)}</example>
  </function>
  <function>
    <description>获取常量</description>
    <name>getConst</name>
    <function-class>com.gisquest.djgx.common.config.Global</function-class>
    <function-signature>java.lang.Object getConst(java.lang.String)</function-signature>
    <example>${fns:getConst(key)}</example>
  </function>
  
  <!-- UserUtils -->
  <function>
    <description>获取当前用户对象</description>
    <name>getUser</name>
    <function-class>com.gisquest.djgx.modules.sys.utils.UserUtils</function-class>
    <function-signature>com.gisquest.djgx.modules.sys.entity.User getUser()</function-signature>
    <example>${fns:getUser()}</example>  
  </function>
  <function>
    <description>根据ID获得用户对象</description>
    <name>getUserById</name>
    <function-class>com.gisquest.djgx.modules.sys.utils.UserUtils</function-class>
    <function-signature>com.gisquest.djgx.modules.sys.entity.User getUserById(java.lang.String)</function-signature>
    <example>${fns:getUserById(id)}</example>  
  </function>
  
  <function>
    <description>获取授权用户信息</description>
    <name>getPrincipal</name>
    <function-class>com.gisquest.djgx.modules.sys.utils.UserUtils</function-class>
    <function-signature>com.gisquest.djgx.modules.sys.security.SystemAuthorizingRealm.Principal getPrincipal()</function-signature>
    <example>${fns:getPrincipal()}</example>  
  </function>
  
  <function>
    <description>获取当前用户的菜单对象列表</description>
    <name>getMenuList</name>
    <function-class>com.gisquest.djgx.modules.sys.utils.UserUtils</function-class>
    <function-signature>java.util.List getMenuList()</function-signature>
    <example>${fns:getMenuList()}</example>  
  </function>
  
  <function>
    <description>获取当前用户的区域对象列表</description>
    <name>getAreaList</name>
    <function-class>com.gisquest.djgx.modules.sys.utils.UserUtils</function-class>
    <function-signature>java.util.List getAreaList()</function-signature>
    <example>${fns:getAreaList()}</example>  
  </function>
  
  <function>
    <description>获取当前用户的部门对象列表</description>
    <name>getOfficeList</name>
    <function-class>com.gisquest.djgx.modules.sys.utils.UserUtils</function-class>
    <function-signature>java.util.List getOfficeList()</function-signature>
    <example>${fns:getOfficeList()}</example>  
  </function>
  
  <function>
    <description>获取当前用户缓存</description>
    <name>getCache</name>
    <function-class>com.gisquest.djgx.modules.sys.utils.UserUtils</function-class>
    <function-signature>java.lang.Object getCache(java.lang.String, java.lang.Object)</function-signature>
    <example>${fns:getCache(cacheName, defaultValue)}</example>  
  </function>
	
  <!-- DictUtils -->
  <function>
    <description>获取字典标签</description>
    <name>getDictLabel</name>
    <function-class>com.gisquest.djgx.modules.sys.utils.DictUtils</function-class>
    <function-signature>java.lang.String getDictLabel(java.lang.String, java.lang.String, java.lang.String)</function-signature>
    <example>${fns:getDictLabel(value, type, defaultValue)}</example>  
  </function>
  
  <function>
    <description>获取字典标签(多个)</description>
    <name>getDictLabels</name>
    <function-class>com.gisquest.djgx.modules.sys.utils.DictUtils</function-class>
    <function-signature>java.lang.String getDictLabels(java.lang.String, java.lang.String, java.lang.String)</function-signature>
    <example>${fns:getDictLabels(values, type, defaultValue)}</example>  
  </function>

  <function>
    <description>获取字典值</description>
    <name>getDictValue</name>
    <function-class>com.gisquest.djgx.modules.sys.utils.DictUtils</function-class>
    <function-signature>java.lang.String getDictValue(java.lang.String, java.lang.String, java.lang.String)</function-signature>
    <example>${fns:getDictValue(label, type, defaultValue)}</example>  
  </function>
  
  <function>
    <description>获取字典对象列表</description>
    <name>getDictList</name>
    <function-class>com.gisquest.djgx.modules.sys.utils.DictUtils</function-class>
    <function-signature>java.util.List getDictList(java.lang.String)</function-signature>
    <example>${fns:getDictList(type)}</example>  
  </function>
  
  <!-- Encodes -->
  <function>
    <description>URL编码</description>
    <name>urlEncode</name>
    <function-class>com.gisquest.djgx.common.utils.Encodes</function-class>
    <function-signature>java.lang.String urlEncode(java.lang.String)</function-signature>
    <example>${fns:urlEncode(part)}</example>  
  </function>
  <function>
    <description>URL解码</description>
    <name>urlDecode</name>
    <function-class>com.gisquest.djgx.common.utils.Encodes</function-class>
    <function-signature>java.lang.String urlDecode(java.lang.String)</function-signature>
    <example>${fns:urlDecode(part)}</example>  
  </function>
  <function>
    <description>HTML编码</description>
    <name>escapeHtml</name>
    <function-class>com.gisquest.djgx.common.utils.Encodes</function-class>
    <function-signature>java.lang.String escapeHtml(java.lang.String)</function-signature>
    <example>${fns:escapeHtml(html)}</example>  
  </function>
  <function>
    <description>HTML解码</description>
    <name>unescapeHtml</name>
    <function-class>com.gisquest.djgx.common.utils.Encodes</function-class>
    <function-signature>java.lang.String unescapeHtml(java.lang.String)</function-signature>
    <example>${fns:unescapeHtml(html)}</example>  
  </function>
  
  <!-- StringUtils -->
  <function>
    <description>从后边开始截取字符串</description>
    <name>substringAfterLast</name>
    <function-class>org.apache.commons.lang3.StringUtils</function-class>
    <function-signature>java.lang.String substringAfterLast(java.lang.String, java.lang.String)</function-signature>
    <example>${fns:substringAfterLast(str,separator)}</example>  
  </function>
  <function>
    <description>判断字符串是否以某某开头</description>
    <name>startsWith</name>
    <function-class>org.apache.commons.lang3.StringUtils</function-class>
    <function-signature>boolean startsWith(java.lang.CharSequence, java.lang.CharSequence)</function-signature>
    <example>${fns:startsWith(str,prefix)}</example> 
  </function>
  <function>
    <description>判断字符串是否以某某结尾</description>
    <name>endsWith</name>
    <function-class>org.apache.commons.lang3.StringUtils</function-class>
    <function-signature>boolean endsWith(java.lang.CharSequence, java.lang.CharSequence)</function-signature>
    <example>${fns:endsWith(str,suffix)}</example> 
  </function>
  <function>
    <description>缩写字符串，超过最大宽度用“...”表示</description>
    <name>abbr</name>
    <function-class>com.gisquest.djgx.common.utils.StringUtils</function-class>
    <function-signature>java.lang.String abbr(java.lang.String, int)</function-signature>
    <example>${fns:abbr(str,length)}</example>  
  </function>
  <function>
    <description>替换掉HTML标签后缩写字符串，超过最大宽度用“...”表示</description>
    <name>rabbr</name>
    <function-class>com.gisquest.djgx.common.utils.StringUtils</function-class>
    <function-signature>java.lang.String rabbr(java.lang.String, int)</function-signature>
    <example>${fns:rabbr(str,length)}</example>
  </function>
  <function>
    <description>替换掉HTML标签</description>
    <name>replaceHtml</name>
    <function-class>com.gisquest.djgx.common.utils.StringUtils</function-class>
    <function-signature>java.lang.String replaceHtml(java.lang.String)</function-signature>
    <example>${fns:replaceHtml(html)}</example>  
  </function>
  
  <function>
    <description>转换为JS获取对象值，生成三目运算返回结果。</description>
    <name>jsGetVal</name>
    <function-class>com.gisquest.djgx.common.utils.StringUtils</function-class>
    <function-signature>java.lang.String jsGetVal(java.lang.String)</function-signature>
    <example>${fns:jsGetVal('row.user.id')}  返回：!row?'':!row.user?'':!row.user.id?'':row.user.id</example>  
  </function>
  
  <!-- DateUtils -->
  <function>
    <description>获取当前日期</description>
    <name>getDate</name>
    <function-class>com.gisquest.djgx.common.utils.DateUtils</function-class>
    <function-signature>java.lang.String getDate(java.lang.String)</function-signature>
    <example>${fns:getDate(pattern)}</example>  
  </function>
  <function>
    <description>获取过去的天数</description>
    <name>pastDays</name>
    <function-class>com.gisquest.djgx.common.utils.DateUtils</function-class>
    <function-signature>long pastDays(java.util.Date)</function-signature>
    <example>${fns:pastDays(date)}</example>  
  </function>
  
  <!-- JsonMapper -->
  <function>
    <description>对象转换JSON字符串</description>
    <name>toJson</name>
    <function-class>com.gisquest.djgx.common.mapper.JsonMapper</function-class>
    <function-signature>java.lang.String toJsonString(java.lang.Object)</function-signature>
    <example>${fns:toJson(object)}</example>  
  </function>
</taglib>

相应后台工具代码：

package com.gisquest.djgx.modules.sys.utils;

import java.util.List;
import java.util.Map;

import org.apache.commons.lang3.StringUtils;

import com.gisquest.djgx.common.utils.CacheUtils;
import com.gisquest.djgx.common.utils.SpringContextHolder;
import com.gisquest.djgx.modules.sys.dao.DictDao;
import com.gisquest.djgx.modules.sys.entity.Dict;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;

/**
 * 字典工具类
 * @author Administrator
 * @version 2013-5-29
 */
public class DictUtils {
	
	private static DictDao dictDao = SpringContextHolder.getBean(DictDao.class);

	public static final String CACHE_DICT_MAP = "dictMap";
	
	public static String getDictLabel(String value, String type, String defaultValue){
		if (StringUtils.isNotBlank(type) && StringUtils.isNotBlank(value)){
			for (Dict dict : getDictList(type)){
				if (type.equals(dict.getType()) && value.equals(dict.getValue())){
					return dict.getLabel();
				}
			}
		}
		return defaultValue;
	}
	
	public static String getDictLabels(String values, String type, String defaultValue){
		if (StringUtils.isNotBlank(type) && StringUtils.isNotBlank(values)){
			List<String> valueList = Lists.newArrayList();
			for (String value : StringUtils.split(values, ",")){
				valueList.add(getDictLabel(value, type, defaultValue));
			}
			return StringUtils.join(valueList, ",");
		}
		return defaultValue;
	}

	public static String getDictValue(String label, String type, String defaultLabel){
		if (StringUtils.isNotBlank(type) && StringUtils.isNotBlank(label)){
			for (Dict dict : getDictList(type)){
				if (type.equals(dict.getType()) && label.equals(dict.getLabel())){
					return dict.getValue();
				}
			}
		}
		return defaultLabel;
	}
	
	public static List<Dict> getDictList(String type){
		@SuppressWarnings("unchecked")
		Map<String, List<Dict>> dictMap = (Map<String, List<Dict>>)CacheUtils.get(CACHE_DICT_MAP);
		if (dictMap == null){
			dictMap = Maps.newHashMap();
			for (Dict dict : dictDao.findAllList()){
				List<Dict> dictList = dictMap.get(dict.getType());
				if (dictList != null){
					dictList.add(dict);
				}else{
					dictMap.put(dict.getType(), Lists.newArrayList(dict));
				}
			}
			CacheUtils.put(CACHE_DICT_MAP, dictMap);
		}
		
		List<Dict> dictList = dictMap.get(type);
		if (dictList == null){
			dictList = Lists.newArrayList();
		}
		return dictList;
	}
	
}

前台调用：

<div class="control-group">
			<label class="control-label" for="flag">定时类型:</label>
			<div class="controls">
				<form:select path="flag" onchange="updateClass()">
					<form:options items="${fns:getDictList('696d7f3d414940b79aa962b8c30f989f')}" itemLabel="label" itemValue="value" htmlEscape="false"/>
				</form:select>
			</div>
		</div>