mongotemplate的mapreduce方法

reduce的處理條數超過100時會用兩個reduce處理  第二次調reduce函式時 fixCardValue和chargeDate會重新初始化 然後拋異常

//根據car_no分組，charge_date時間排序，取最近一條記錄的fix_card_value
Criteria criteria = Criteria.where("project_id").is(project_id);
Query query = new Query(criteria);
String map = "function(){"
        + "emit("
        +        "this.car_no,"
        +        "{fixCardValue:this.fix_card_value,chargeDate:this.charge_date}"
        +       ");"
        +  "}";
String reducef = "function(key,values){" +
        "var fixCardValue = values[0].fixCardValue;" +
        "var chargeDate = values[0].chargeDate;"+
        "for(var i=1;i<values.length;i++){" +
        "if(values[i].chargeDate>chargeDate){" +
        "fixCardValue = values[i].fixCardValue};" +
        "} " +
        "return fixCardValue;}";
MapReduceResults<BasicDBObject> mapReduceResults =
        mongoTemplate.mapReduce(query, "charge_data", map, reducef, BasicDBObject.class);
Iterator iterator = mapReduceResults.iterator();
while (iterator.hasNext()) {
    String jsonString = iterator.next().toString();
    JSONObject jsonObject = JSONObject.parseObject(jsonString);
    String key = jsonObject.getString("_id");
    int  value = jsonObject.getJSONObject("value").getDouble("fixCardValue").intValue();
 }
 

 reduce的處理條數超過100時會用兩個reduce處理  第二次調reduce函式時 fixCardValue和chargeDate會重新初始化 然後拋異常

將reduce函式改下如下方式：

String reducef = "function(key,values){" +
        "var fixCardValue = 999;" +
        "var chargeDate = '1970-01-01';" +
        "for(var i=0;i<values.length;i++){" +
        "if(values[i].chargeDate>chargeDate){" +
        "fixCardValue = values[i].fixCardValue};" +
        "} " +
        "return fixCardValue;}";