使用KSTREAM或KSQL将java JSON数组转换为JSON对象

Question

我有以下格式的数据输入卡夫卡

{"WHS":[{"Character Set":"UTF-8","action":"finished","Update-Date-Time":"2020-04-11 09:00:02:25","Number":0,"Abbr":"","Name":"","Name2":"","Country-Code":"","Addr-1":"","Addr-2":"","Addr-3":"","Addr-4":"","City":"","State":""}]}

我想把它变成这样

{"Character Set":"UTF-8","action":"finished","Update-Date-Time":"2020-04-11 09:00:02:25","Number":0,"Abbr":"","Name":"","Name2":"","Country-Code":"","Addr-1":"","Addr-2":"","Addr-3":"","Addr-4":"","City":"","State":""}

我试图使用ksql实现扁平化，但ksql还不支持数组

我试着用下面的代码使用kstream将其展平

builder.stream(inputTopic).flatMapValues(Object -> Arrays.asList()).to(outputTopic);

但它没有产生任何产出。对此，我们将不胜感激

Answer 1

KSQL/ksqlDB确实支持阵列。下面是如何用它来实现你的要求：

  Declare the stream
CREATE STREAM TEST1 
    (WHS ARRAY<STRUCT<"action"           VARCHAR
                    , "Update-Date-Time" VARCHAR
                    , "Number"           VARCHAR
                    , "Abbr"             VARCHAR
                    , "Name"             VARCHAR
                    , "Name2"            VARCHAR
                    , "Country-Code"     VARCHAR
                    , "Addr-1"           VARCHAR
                    , "Addr-2"           VARCHAR
                    , "Addr-4"           VARCHAR
                    , "City"             VARCHAR
                    , "State"            VARCHAR>>) 
    WITH (KAFKA_TOPIC ='test1'
         ,VALUE_FORMAT='JSON');

  Set querying from beginning of the topic
SET 'auto.offset.reset' = 'earliest';

  Query the array         
ksql> SELECT WHS FROM TEST1 EMIT CHANGES LIMIT 1;
+                                                                           +
|WHS                                                                                                                                                   |
+                                                                           +
|[{ACTION=finished, Update-Date-Time=2020-04-11 09:00:02:25, NUMBER=0, ABBR=, NAME=, NAME2=, Country-Code=, Addr-1=, Addr-2=, Addr-4=, City=, STATE=}] |
Limit Reached
Query terminated
ksql>         

  Flatten the array
ksql> SELECT EXPLODE(WHS) FROM TEST1 EMIT CHANGES LIMIT 1;
+                                                                                                                                            -+
|KSQL_COL_0                                                                                                                                                                                                                                                                               |
+                                                                                                                                            -+
|{ACTION=finished, Update-Date-Time=2020-04-11 09:00:02:25, NUMBER=0, ABBR=, NAME=, NAME2=, Country-Code=, Addr-1=, Addr-2=, Addr-4=, City=, STATE=}                                                                                                                                      |
Limit Reached
Query terminated
ksql>

您可以将其写入另一个流（主题）：

ksql> CREATE STREAM TEST1_EXPLODE WITH (KAFKA_TOPIC='NEW_TEST1') AS SELECT EXPLODE(WHS) FROM TEST1 EMIT CHANGES;

 Message
                     -
 Created query with ID CSAS_TEST1_EXPLODE_155
                     -
ksql> PRINT NEW_TEST1;
…
Value format: JSON or KAFKA_STRING
rowtime: 4/27/20 8:28:46 AM UTC, key: <null>, value: {"KSQL_COL_0":{"ACTION":"finished","Update-Date-Time":"2020-04-11 09:00:02:25","NUMBER":"0","ABBR":"","NAME":"","NAME2":"","Country-Code":"","Addr-1":"","Addr-2":"","Addr-4":"","City":"","STATE":""}}

如果要展平生成的结构，也可以这样做：

CREATE STREAM TEST1_FLATTENED AS SELECT  EXPLODE(WHS)->"action"           AS "action"           ,
        EXPLODE(WHS)->"Update-Date-Time" AS "Update-Date-Time" ,
        EXPLODE(WHS)->"Number"           AS "Number"           ,
        EXPLODE(WHS)->"Abbr"             AS "Abbr"             ,
        EXPLODE(WHS)->"Name"             AS "Name"             ,
        EXPLODE(WHS)->"Name2"            AS "Name2"            ,
        EXPLODE(WHS)->"Country-Code"     AS "Country-Code"     ,
        EXPLODE(WHS)->"Addr-1"           AS "Addr-1"           ,
        EXPLODE(WHS)->"Addr-2"           AS "Addr-2"           ,
        EXPLODE(WHS)->"Addr-4"           AS "Addr-4"           ,
        EXPLODE(WHS)->"City"             AS "City"             ,
        EXPLODE(WHS)->"State"            AS "State"
    FROM TEST1 EMIT CHANGES;

ksql> PRINT TEST1_FLATTENED;
…
Value format: JSON or KAFKA_STRING
rowtime: 4/27/20 8:28:46 AM UTC, key: <null>, value: {"action":"finished","Update-Date-Time":"2020-04-11 09:00:02:25","Number":"0","Abbr":"","Name":"","Name2":"","Country-Code":"","Addr-1":"","Addr-2":"","Addr-4":"","City":"","State":""}