Freemarker(一):自定义标签

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package utils;

import freemarker.core.Environment;
import freemarker.template.*;
import java.io.IOException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import models.cms.BcColumn;

/**
 *
 * @author Adam
 */
public class ColumnDirective implements TemplateDirectiveModel {

    public void execute(Environment env, Map params, TemplateModel[] loopVars, TemplateDirectiveBody body) throws TemplateException, IOException {
        // 获取传递进来的参数 
        Iterator it = params.entrySet().iterator();
        while (it.hasNext()) {
            Map.Entry entry = (Map.Entry) it.next();
            String paramName = entry.getKey().toString();
            TemplateModel paramValue = (TemplateModel) entry.getValue();
            if (paramName.equals("size")){
                if (!(paramValue instanceof TemplateNumberModel)) { 
                    throw new TemplateModelException("The size parameter " + "must be a number."); 
                }
            }else{
                throw new TemplateModelException("Unsupported parameter: "  + paramName);
            }
        }

        Map<String, Object> map = get(params);
        if (body != null) {
            env.setVariable("list", DefaultObjectWrapper.DEFAULT_WRAPPER.wrap(map.get("list")));
            body.render(env.getOut());
        } else {
            throw new RuntimeException("missing body");
        }
    }

    private Map<String, Object> get(Map params) {
        Integer size = Integer.valueOf(params.get("size").toString());

        Map<String, Object> map = new HashMap<String, Object>();
        List<BcColumn> list = BcColumn.find("order by createDate desc").fetch(size);
        map.put("list", list);
        return map;
    }
}