org.apache.hadoop.hive.serde2.SerDeException: Row is not a valid JSON Object
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重要的是每行必须是一个完整的JSON,一个JSON不能跨越多行,也就是说,serde不会对多行的Json有效。 因为这是由Hadoop处理文件的工作方式决定,文件必须是可拆分的,例如,Hadoop将在行尾分割文本文件。
// this will work{ "key" : 10 }// this will not work{ "key" : 10 }
2. 下载Jar
使用之前先下载jar:
http://www.congiu.net/hive-json-serde/
如果要想在Hive中使用JsonSerde,需要把jar添加到Hive类路径中:
add jar json-serde-1.3.7-jar-with-dependencies.jar;
3. 与数组使用
源数据:
{"country":"Switzerland","languages":["German","French","Italian"]}{"country":"China","languages":["chinese"]}
Hive表:
CREATE TABLE tmp_json_array ( country string, languages array<string> )ROW FORMAT SERDE 'org.openx.data.jsonserde.JsonSerDe'STORED AS TEXTFILE;LOAD DATA LOCAL INPATH '/home/xiaosi/a.txt' OVERWRITE INTO TABLE tmp_json_array;
使用:
hive> select languages[0] from tmp_json_array;OKGermanchineseTime taken: 0.096 seconds, Fetched: 2 row(s)
4. 嵌套结构
源数据:
{"country":"Switzerland","languages":["German","French","Italian"],"religions":{"catholic":[6,7]}}{"country":"China","languages":["chinese"],"religions":{"catholic":[10,20],"protestant":[40,50]}}
Hive表:
CREATE TABLE tmp_json_nested ( country string, languages array<string>, religions map<string,array<int>>)ROW FORMAT SERDE 'org.openx.data.jsonserde.JsonSerDe'STORED AS TEXTFILE;LOAD DATA LOCAL INPATH '/home/xiaosi/a.txt' OVERWRITE INTO TABLE tmp_json_nested ;
使用:
hive> select * from tmp_json_nested;OKSwitzerland["German","French","Italian"]{"catholic":[6,7]}China["chinese"]{"catholic":[10,20],"protestant":[40,50]}Time taken: 0.113 seconds, Fetched: 2 row(s)hive> select languages[0] from tmp_json_nested;OKGermanchineseTime taken: 0.122 seconds, Fetched: 2 row(s)hive> select religions['catholic'][0] from tmp_json_nested;OK610Time taken: 0.111 seconds, Fetched: 2 row(s)
5. 坏数据
格式错误的数据的默认行为是抛出异常。 例如,对于格式不正确的json(languages后缺少':'):
{"country":"Italy","languages"["Italian"],"religions":{"protestant":[40,50]}}
使用:
hive> LOAD DATA LOCAL INPATH '/home/xiaosi/a.txt' OVERWRITE INTO TABLE tmp_json_nested ;Loading data to table default.tmp_json_nestedOKTime taken: 0.23 secondshive> select * from tmp_json_nested;OKFailed with exception java.io.IOException:org.apache.hadoop.hive.serde2.SerDeException: Row is not a valid JSON Object - JSONException: Expected a ':' after a key at 31 [character 32 line 1]Time taken: 0.096 seconds
这种方式不是一种好的策略,我们数据中难免会遇到坏数据。如下操作可以忽略坏数据:
ALTER TABLE json_table SET SERDEPROPERTIES ( "ignore.malformed.json" = "true");
更改设置后:
hive> ALTER TABLE tmp_json_nested SET SERDEPROPERTIES ( "ignore.malformed.json" = "true");OKTime taken: 0.122 secondshive> select * from tmp_json_nested;OKSwitzerland["German","French","Italian"]{"catholic":[6,7]}China["chinese"]{"catholic":[10,20],"protestant":[40,50]}NULLNULLNULLTime taken: 0.103 seconds, Fetched: 3 row(s)
现在不会导致查询失败,但是坏数据记录将变为NULL NULL NULL。
注意:
如果JSON格式正确,但是不符合Hive范式,则不会跳过,依然会报错:
{"country":"Italy","languages":"Italian","religions":{"catholic":"90"}}
使用:
hive> ALTER TABLE tmp_json_nested SET SERDEPROPERTIES ( "ignore.malformed.json" = "true");OKTime taken: 0.081 secondshive> select * from tmp_json_nested;OKFailed with exception java.io.IOException:org.apache.hadoop.hive.ql.metadata.HiveException: java.lang.ClassCastException:java.lang.String cannot be cast to org.openx.data.jsonserde.json.JSONArrayTime taken: 0.097 seconds
6. 将标量转为数组
这是一个常见的问题,某一个字段有时是一个标量,有时是一个数组,例如:
{ field: "hello", .. }{ field: [ "hello", "world" ], ...
在这种情况下,如果将表声明为array<string>,如果SerDe找到一个标量,它将返回一个单元素的数组,从而有效地将标量提升为数组。 但是标量必须是正确的类型。
7. 映射Hive关键词
有时可能发生的是,JSON数据具有名为hive中的保留字的属性。 例如,您可能有一个名为“timestamp”的JSON属性,它是hive中的保留字,当发出CREATE TABLE时,hive将失败。 此SerDe可以使用SerDe属性将hive列映射到名称不同的属性。
{"country":"Switzerland","exec_date":"2017-03-14 23:12:21"}{"country":"China","exec_date":"2017-03-16 03:22:18"}
CREATE TABLE tmp_json_mapping ( country string, dt string)ROW FORMAT SERDE 'org.openx.data.jsonserde.JsonSerDe'WITH SERDEPROPERTIES ("mapping.dt"="exec_date")STORED AS TEXTFILE;
hive> select * from tmp_json_mapping;OKSwitzerland2017-03-14 23:12:21China2017-03-16 03:22:18Time taken: 0.081 seconds, Fetched: 2 row(s)
“mapping.dt”,表示dt列读取JSON属性为exec_date的值。
原文:http://blog.csdn.net/sunnyyoona/article/details/70170173
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