Elasticsearch cannot write xcontent for unknown value of type class java.sql.Timestamp
在使用Elasticsearch进行index数据时，发现报错如下：
java.lang.IllegalArgumentException: cannot write xcontent for unknown value of type class java.math.Timestamp
at org.elasticsearch.common.xcontent.XContentBuilder.unknownValue(XContentBuilder.java:755)
at org.elasticsearch.common.xcontent.XContentBuilder.value(XContentBuilder.java:726)
at org.elasticsearch.common.xcontent.XContentBuilder.field(XContentBuilder.java:711)
at org.elasticsearch.index.query.BaseTermQueryBuilder.doXContent(BaseTermQueryBuilder.java:154)
at org.elasticsearch.index.query.AbstractQueryBuilder.toXContent(AbstractQueryBuilder.java:82)
at org.elasticsearch.index.query.BoolQueryBuilder.doXArrayContent(BoolQueryBuilder.java:275)
at org.elasticsearch.index.query.BoolQueryBuilder.doXContent(BoolQueryBuilder.java:256)
at org.elasticsearch.index.query.AbstractQueryBuilder.toXContent(AbstractQueryBuilder.java:82)
at org.elasticsearch.common.xcontent.XContentBuilder.value(XContentBuilder.java:779)
at org.elasticsearch.common.xcontent.XContentBuilder.value(XContentBuilder.java:772)
at org.elasticsearch.common.xcontent.XContentBuilder.field(XContentBuilder.java:764)
at org.elasticsearch.search.builder.SearchSourceBuilder.toXContent(SearchSourceBuilder.java:1184)
at org.elasticsearch.common.xcontent.XContentHelper.toXContent(XContentHelper.java:349)
at org.elasticsearch.search.builder.SearchSourceBuilder.toString(SearchSourceBuilder.java:1558)
at org.elasticsearch.search.builder.SearchSourceBuilder.toString(SearchSourceBuilder.java:1553)
at java.lang.String.valueOf(String.java:2994)
at java.lang.StringBuilder.append(StringBuilder.java:131)
at org.elasticsearch.action.search.SearchRequest.toString(SearchRequest.java:516)
以上此类问题找不到对应的数据类型type
从异常信息看，显然ES无法接受Timestamp类型，本文使用es版本未6.3.2，目前的解决办法是：转换别的es支持的数据类型。
参考：ELK系列(4) – Elasticsearch cannot write xcontent for unknown value of type class java.math.BigDecimal
参考：[elastic search 5.4.版本，java api 调用出现：can not write type [class java.math.BigDecimal]](