Freemarker 自定义标签 简单案例

package com.eagles.directive; import java.io.IOException; import java.io.Writer; import java.util.Iterator; import java.util.Map; import freemarker.core.Environment; import freemarker.template.SimpleNumber; import freemarker.template.TemplateBooleanModel; import freemarker.template.TemplateDirectiveBody; import freemarker.template.TemplateDirectiveModel; import freemarker.template.TemplateException; import freemarker.template.TemplateModel; import freemarker.template.TemplateModelException; import freemarker.template.TemplateNumberModel; /** * FreeMarker 自定义标签实现重复输出内容体。 * * * 参数: * count: 重复的次数，必须的且非负整数。 * hr: 设置是否输出HTML标签 "hr" 元素. Boolean. 可选的默认为fals. * * * 循环变量: 只有一个，可选的. 从1开始。 * * */ public class RepeatDirective implements TemplateDirectiveModel { private static final String PARAM_NAME_COUNT = "count1"; private static final String PARAM_NAME_HR = "hr"; public void execute(Environment env, Map params, TemplateModel[] loopVars, TemplateDirectiveBody body) throws TemplateException, IOException { // 处理参数 int countParam = 0; boolean countParamSet = false; boolean hrParam = false; Iterator paramIter = params.entrySet().iterator(); while (paramIter.hasNext()) { Map.Entry ent = (Map.Entry) paramIter.next(); String paramName = (String) ent.getKey(); TemplateModel paramValue = (TemplateModel) ent.getValue(); if (paramName.equals(PARAM_NAME_COUNT)) { if (!(paramValue instanceof TemplateNumberModel)) { throw new TemplateModelException("The \"" + PARAM_NAME_HR + "\" parameter " + "must be a number."); } countParam = ((TemplateNumberModel) paramValue).getAsNumber() .intValue(); countParamSet = true; if (countParam < 0) { throw new TemplateModelException("The \"" + PARAM_NAME_HR + "\" parameter " + "can't be negative."); } } else if (paramName.equals(PARAM_NAME_HR)) { if (!(paramValue instanceof TemplateBooleanModel)) { throw new TemplateModelException("The \"" + PARAM_NAME_HR + "\" parameter " + "must be a boolean."); } hrParam = ((TemplateBooleanModel) paramValue).getAsBoolean(); } else { throw new TemplateModelException("Unsupported parameter: " + paramName); } } if (!countParamSet) { throw new TemplateModelException("The required \"" + PARAM_NAME_COUNT + "\" paramter" + "is missing."); } if (loopVars.length > 1) { throw new TemplateModelException( "At most one loop variable is allowed."); } // Yeah, it was long and boring... // --------------------------------------------------------------------- // 真正开始处理输出内容 Writer out = env.getOut(); if (body != null) { for (int i = 0; i < countParam; i++) { // 输出 <hr> 如果 参数hr 设置为true if (hrParam && i != 0) { out.write("<hr>"); } // 设置循环变量 if (loopVars.length > 0) { loopVars[0] = new SimpleNumber(i + 1); } // 执行标签内容(same as <#nested> in FTL). body.render(env.getOut()); } } } }