velocity模板实战

场景：json配置报文转换
遇到的问题：1.json报文转换成map,多节点如何处理？数组如何处理？
2.velocity模板处理数组
3.应用之间rabbitmq通讯map反序列化，数组报错？
知识点：
HashMap map中重要的两个方法map.containsKey()和map.contaisValue()
#foreach($key in [0..10])
$key
#end
#if($id == "")
#end
计数器 velocityCount
haspmap的属性可以在模板中使用
样例报文

 {
     "service":{
         "service_header":{
             "name":"张三",
             "age":"12"
         }
         "service_body":{
              "info":[
                 {
                     "address":"上海",
                     "tel":"111"
                 },
                 {
                     "address":"北京",
                     "tel":"020"
                 }

              ]
         }
     }
  }

　　模板配置

{
     "service":{
         "service_header":{
             "lastname":"${name}",
             "age":"${age}"
         }
         "service_body":{
              "info":[
                  #set($infos={"address":"address","telphone":"tel"})
                          #foreach($key in ${infos})
                          {
                              #foreach($key2 in $key.keySet())
                                 #foreach($key3 in $infos.keySet())
                                    #if($key2 == $infos.get($key3))
                                       "$key3":"$key.get($key2)"
                                        #if($velocityCount != $key.size())
                                         ,
                                        #end
                                    #end
                                 #end
                              #end
                          }
                          #if($velocityCount != $infos.size())
                           ,
                          #end
                        #end
              ]
         }
     }
  } 

测试代码

package com.sunline.nfs.process;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.StringWriter;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Properties;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

import org.apache.velocity.Template;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.Velocity;
import org.apache.velocity.app.VelocityEngine;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;

public class velocityEngine {
    static Map<String,Object> jsonMap = new LinkedHashMap<String,Object>();

    public static Map recursinMap(Map<String,Object> map){
        net.sf.json.JSONObject jObject = new net.sf.json.JSONObject();
        for(String key:map.keySet()){
            String str = map.get(key).toString();
            if(str.startsWith("{")){
                /*com.alibaba.fastjson.JSONObject jObject = JSON.parseObject(str);*/
                Map<String,Object> map2 = jObject.fromObject(str);
                if(!map.toString().endsWith(map2.toString()+"}")){
                    int i = map.toString().indexOf(map2.toString())+1;
                    String value ="{" + map.toString().substring((i+map2.toString().length()),map.toString().length());
                    map2.put(key, value);
                }
                return recursinMap(map2);
            }
            else{
                if(str.startsWith("[")){
                    JSONArray tmpMaps = JSONArray.fromObject(str);
                    System.out.println("key="+key+" tmpMaps"+tmpMaps);
                    jsonMap.put(key, tmpMaps);
                    /*for(int i=0;i<tmpMaps.size();i++){
                        JSONObject job = tmpMaps.getJSONObject(i);
                        Map<String,Object> jobMap = JSONObject.fromObject(job.toString());
                        for(String key2:jobMap.keySet())
                            jsonMap.put(key+i+key2, jobMap.get(key2));
                    }        */
                }
                else{
                    jsonMap.put(key, str);
                }

            }
        }
        return jsonMap;
    }
    @SuppressWarnings("null")
    public static void main(String[] args) throws IOException{
        String filename = "ObtainAppNo.txt";
        String json = readJson(filename);
        net.sf.json.JSONObject jObject = new net.sf.json.JSONObject();
        Map<String,Object> map2 = jObject.fromObject(json);
        Map<String,Object> jsonMap = recursinMap(map2);
        System.out.println("-----" +jsonMap);
        //初始化参数
        Properties properties=new Properties();
        //设置velocity资源加载方式为class
        properties.setProperty("resource.loader", "class");
        //设置velocity资源加载方式为file时的处理类
        properties.setProperty("class.resource.loader.class", "org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader");
        //实例化一个VelocityEngine对象
        VelocityEngine velocityEngine=new VelocityEngine(properties);

        //实例化一个VelocityContext
        VelocityContext context=new VelocityContext();
        for(Object key :jsonMap.keySet()){
            context.put((String)key, jsonMap.get(key));
        }
        //实例化一个StringWriter
        StringWriter writer=new StringWriter();
      //假若在com.velocity.test包下有一个hello.vm文件,那么加载路径为com/velocity/test/hello.vm
       // String json2 = readJson("2.txt");
       // velocityEngine.mergeTemplate(json2, "gbk", context, writer);
        //这种方式是正确的
        velocityEngine.mergeTemplate("2.txt", "gbk", context, writer);
        String str = writer.toString();
        str = str.replaceAll("\\s*", "");
        System.out.println("-----" +str);

    }
    public static String readJson(String filename){
        Resource resource =new  ClassPathResource(filename);
        File file;
        try {
            file = resource.getFile();
            BufferedReader reader= new BufferedReader(new FileReader(file));
            String temp=null;
            String str="";
            while((temp=reader.readLine())!=null){
                str = str + temp;
            }
            str=str.replace(" ", "");
            return str;
        } catch (IOException e) {
            e.printStackTrace();
        }

        return null;
    }

}

原文地址：https://www.cnblogs.com/mutong1228/p/8987519.html