freemarker自定义标签（与java合用）

Posted 2020-10-24 星朝

自定义类继承FreemarkerManager类，重写protected Configuration createConfiguration(ServletContext servletContext)throws TemplateException方法定义有哪些TemplateDirectiveModel类与它的别名[自定义标签名称]，通过Spring来取：

import java.util.Map;
import javax.servlet.ServletContext;
import org.apache.struts2.views.freemarker.FreemarkerManager;
import org.springframework.context.ApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;
import freemarker.template.Configuration;
import freemarker.template.TemplateDirectiveModel;
import freemarker.template.TemplateException;
/**
 * 从spring取得所有的TemplateDirectiveModel类的对象，全部取出来，交给struts管理
 * @author Administrator

 * */
public class DirectiveFreemarkerManager extends FreemarkerManager{
    @Override
    protected Configuration createConfiguration(ServletContext servletContext)
            throws TemplateException {
        //调用你父类操作
        Configuration  configuration=super.createConfiguration(servletContext);
        //设定在页面使用的标签的类型 (([]、<>),[]这种标记解析要快些)      [] SQUARE_BRACKET_TAG_SYNTAX  ,  <>ANGLE_BRACKET_TAG_SYNTAX
        configuration.setTagSyntax(Configuration.AUTO_DETECT_TAG_SYNTAX);
        //取得spring所管理所有的对象 ClassPathXmlApplication,  WebAplicationContext
        ApplicationContext  appContext=WebApplicationContextUtils.getRequiredWebApplicationContext(servletContext);
        // 获取实现TemplateDirectiveModel的bean
        Map<String, TemplateDirectiveModel>  beans= appContext.getBeansOfType(TemplateDirectiveModel.class);
        //再把这些类，全部交给struts的freemarker来管理
        //Component("upper") public class UpperDirective implements TemplateDirectiveModel
        for(String key : beans.keySet()){
            Object obj=beans.get(key);  //TemplateDirectiveModel
            if(obj!=null && obj instanceof  TemplateDirectiveModel){
                configuration.setSharedVariable(key, obj);
            } 
        }
        return configuration;
    }}

在struts.xml中添加：

 <!-- 让struts来管理freemarker自定义标签类 struts.freemarker.manager.classname=org.apache.struts2.views.freemarker.FreemarkerManager -->    <constant name="struts.freemarker.manager.classname" value="com.xxxx.struts.DirectiveFreemarkerManager"></constant>

编写TemplateDirectiveModel，并交给Spring管理：

import java.io.IOException;
import java.io.Writer;
import java.util.Map;
import org.springframework.stereotype.Component;
import freemarker.core.Environment;
import freemarker.template.TemplateDirectiveBody;
import freemarker.template.TemplateDirectiveModel;
import freemarker.template.TemplateException;
import freemarker.template.TemplateModel;
import freemarker.template.TemplateModelException;

/**
 * 自定义指定，作用，把嵌套的内容中的小写全部转换为大写字母
 * 
 * @author Administrator

 *
 */
@Component("upper")
public class UpperDirective implements TemplateDirectiveModel {
    //evn  环境输出
    //params 参数
    //loopVars 循环
    //body   内容
    @Override
    public void execute(Environment env, Map params,
            TemplateModel[] loopVars, TemplateDirectiveBody body)
            throws TemplateException, IOException {
        //如果有参数 应该不支持参数
        if(!params.isEmpty()){
            throw new TemplateModelException(
                    "这个指令不允许使用参数.");
        }
        if(loopVars.length!=0){
              throw new TemplateModelException(
                        "这个指令不允许使用循环参数.");
        }
         // 如果嵌套内容不为空的
        if(body!=null){
            //如果有内容，自己去重写输出流
            body.render( new UpperCaseFilterWriter(env.getOut()));

                }else{
            throw new RuntimeException("无内容异常");
        }
    }
    //内部类
    private static class UpperCaseFilterWriter extends Writer{
         private final Writer out;  //接收网页中的输出 流对象
         public UpperCaseFilterWriter(Writer out){
             this.out=out;
         }
          //cbuf 文字内容， off位移，len 文字长度
        @Override
        public void write(char[] cbuf, int off, int len) throws IOException {
            char[] transformedChar=new char[len];
            for(int i=0;i<len;i++){
                transformedChar[i]=Character.toUpperCase(cbuf[i+off]);
            }
            out.write(transformedChar); 
        }
        @Override        public void flush() throws IOException {
          out.flush();
        }
        @Override
        public void close() throws IOException {
             out.close();
        } 
    }
}

编写action,result—>字符串，type=”freemarker”：

<!-- 约定大于配置   /admin/Flinktype_list.action  --> 
   <package name="freemarkerPackage" namespace="/admin" extends="commonPackage" >
       <action name="*_*" class="{1}Action" method="{2}">
           <result name="{2}" type="freemarker">/admin/template/{1}/{2}.ftl</result> 
       </action>
   </package>

模板/template/upper.ftl：

<!DOCTYPE html>
<html lang="ch-ZN">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta name="description" content="">
<meta name="author" content="">
<title>freemarker自定义标签</title></head>
<body>  

    <@upper>
          bar          <#-- All kind of FTL is allowed here -->
          <#list ["red", "green", "blue"] as color>
            ${color}
          </#list>
          baaz
     </@upper>


             <hr/>

        <@cms_linktype    limit="0,10" >
         请选择分类: <select>
               <#list  arrTypes as x>
                  <option value="${x.id}">${x.typeName}</option>
               </#list> 
         </select>
    </@cms_linktype>
</body>