Freemarker自定义标签配置流程
在这里通过JEECMS所使用的架构来描述Freemarker自定义标签配置流程，以@cms_content_list为例来说明，在一个HTML中引用标签的实例代码如下：
[@cms_content_list typeId='2' count='5' orderBy='9' channelId='75' channelOption='0']
[#list tag_list as a]
[@text_cut s=a.title len='19' append='...' /]
[#if a_index<1]
[@text_cut s=a.description! len='34' append='...' /][/#if]
[/#list]
[/@cms_content_list]
为了能够使用上面的标签我们只需要做如下三个步骤就能实现：
1.定义实现此标签功能的Class
自定义标签需要实现TemplateDirectiveModel这个接口中的execute方法 实例代码如下：
package com.jeecms.cms.action.directive;
import static com.jeecms.cms.Constants.TPL_STYLE_LIST;
import static com.jeecms.cms.Constants.TPL_SUFFIX;
import static com.jeecms.common.web.Constants.UTF8;
import static com.jeecms.common.web.freemarker.DirectiveUtils.OUT_LIST;
import static com.jeecms.core.web.util.FrontUtils.PARAM_STYLE_LIST;
import java.io.IOException;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.commons.lang.StringUtils;
import com.jeecms.cms.action.directive.abs.AbstractContentDirective;
import com.jeecms.cms.entity.main.Content;
import com.jeecms.common.web.freemarker.DefaultObjectWrapperBuilderFactory;
import com.jeecms.common.web.freemarker.DirectiveUtils;
import com.jeecms.common.web.freemarker.ParamsRequiredException;
import com.jeecms.common.web.freemarker.DirectiveUtils.InvokeType;
import com.jeecms.core.entity.CmsSite;
import com.jeecms.core.web.util.FrontUtils;
import freemarker.core.Environment;
import freemarker.template.TemplateDirectiveBody;
import freemarker.template.TemplateException;
import freemarker.template.TemplateModel;
/**
* 内容列表标签
*/
public class ContentListDirective extends AbstractContentDirective {
/**
* 模板名称
*/
public static final String TPL_NAME = "content_list";
/**
* 输入参数，文章ID。允许多个文章ID，用","分开。排斥其他所有筛选参数。
*/
public static final String PARAM_IDS = "ids";
@SuppressWarnings("unchecked")
public void execute(Environment env, Map params, TemplateModel[] loopVars,
TemplateDirectiveBody body) throws TemplateException, IOException {
CmsSite site = FrontUtils.getSite(env);
List list = getList(params, env);
Map paramWrap = new HashMap(
params);
paramWrap.put(OUT_LIST, DefaultObjectWrapperBuilderFactory.getDefaultObjectWrapper().wrap(list));
Map origMap = DirectiveUtils
.addParamsToVariable(env, paramWrap);
InvokeType type = DirectiveUtils.getInvokeType(params);
String listStyle = DirectiveUtils.getString(PARAM_STYLE_LIST, params);
if (InvokeType.sysDefined == type) {
if (StringUtils.isBlank(listStyle)) {
throw new ParamsRequiredException(PARAM_STYLE_LIST);
}
env.include(TPL_STYLE_LIST + listStyle + TPL_SUFFIX, UTF8, true);
} else if (InvokeType.userDefined == type) {
if (StringUtils.isBlank(listStyle)) {
throw new ParamsRequiredException(PARAM_STYLE_LIST);
}
FrontUtils.includeTpl(TPL_STYLE_LIST, site, env);
} else if (InvokeType.custom == type) {
FrontUtils.includeTpl(TPL_NAME, site, params, env);
} else if (InvokeType.body == type) {
body.render(env.getOut());
} else {
throw new RuntimeException("invoke type not handled: " + type);
}
DirectiveUtils.removeParamsFromVariable(env, paramWrap, origMap);
}
@SuppressWarnings("unchecked")
protected List getList(Map params,
Environment env) throws TemplateException {
Integer[] ids = DirectiveUtils.getIntArray(PARAM_IDS, params);
if (ids != null) {
return contentMng.getListByIdsForTag(ids, getOrderBy(params));
} else {
return (List) super.getData(params, env);
}
}
@Override
protected boolean isPage() {
return false;
}
}
2.把类进行Spring中注册，形成Spring Bean
在JEECMS中，所有的标签类都是在jeecms-context.xml中进行注册的，注册代码如下：
3.将spring bean 配置到freemarkerConfig全局变量中去
FreemarkerConfig是Freemarker的一个全局变量配置，便于Freemarker能够通过标签查找到标签实现类，在JEECMS中，FreemarkerConfig Bean配置在jeecms-servlet-front.xml文件中，如代码所示：
auto_detect
5
UTF-8
UTF-8
zh_CN
true,false
yyyy-MM-dd HH:mm:ss
yyyy-MM-dd
HH:mm:ss
0.######
true
/WEB-INF/ftl/jeecms/index.ftl as p,/WEB-INF/ftl/spring.ftl as s
而对于配置文件中有一属性FreemarkerVariables是用来配置自定义标签的实现类，通过情况下是这样配置的，如下面代码 ：
0
UTF-8
UTF-8
zh_CN
true,false
yyyy-MM-dd HH:mm:ss
yyyy-MM-dd
HH:mm:ss
0.######
true
通过上面可以看到属性值FreemarkerVariables中是一个Map类型，里面的Key指向的是标签实现类，Value是指向的页面中的标签，而在Jeecms中为了配置更多的标签实现类，而Value采用了这样的方式 ：value="#{propertyUtils.getBeanMap('directive.')}"，是通过一个属性类查找对应的配置文件，这个配置文件就是Jeecms.properties，里面的内容如下：
directive.uuid=uuid
directive.process_time=process_time
directive.text_cut=text_cut
directive.html_cut=html_cut
directive.cms_pagination=cms_pagination
directive.cms_channel_list=cms_channel_list
directive.cms_channel_page=cms_channel_page
directive.cms_channel=cms_channel
directive.cms_content=cms_content
directive.cms_content_list=cms_content_list
directive.cms_content_page=cms_content_page
directive.cms_tag_list=cms_tag_list
directive.cms_tag_page=cms_tag_page
directive.cms_topic_list=cms_topic_list
directive.cms_topic_page=cms_topic_page
directive.cms_comment_list=cms_comment_list
directive.cms_comment_page=cms_comment_page
directive.cms_guestbook_ctg_list=cms_guestbook_ctg_list
directive.cms_guestbook_list=cms_guestbook_list
directive.cms_guestbook_page=cms_guestbook_page
directive.cms_vote=cms_vote
directive.cms_lucene_list=cms_lucene_list
directive.cms_lucene_page=cms_lucene_page
directive.cms_friendlink_ctg_list=cms_friendlink_ctg_list
directive.cms_friendlink_list=cms_friendlink_list
directive.cms_advertising=cms_advertising
directive.cms_vote_list=cms_vote_list
directive.cms_model=cms_model
directive.cms_score_group=cms_score_group
directive.cms_searchword_list=cms_searchword_list从中可以看出JEECMS中的Key和Value是一样的。
到此为止Freemarker的自定义标签配置流程已经完成，可以正常使用标签了。