How to get Map data using JDBCTemplate queryForMap

Question

How to load data from JDBCTemplate queryForMap   and it returns the Map Interface How the  maintained the query data internally in map I trying to load but i got below exception i e   org springframework dao IncorrectResultSizeDataAccessException  Incorrect result  Code -  public List getUserInfoByAlll         List profilelist new ArrayList        Map m new HashMap        m this jdbctemplate queryForMap  SELECT userid username  FROM USER        Set s m keySet        Iterator it s iterator        while it hasNext             String its  String it next            Object ob  Object m get its           log info  UserDAOImpl  getUserListSize    ob             return profilelist      Plz help me

User · Accepted Answer

queryForMap is appropriate if you want to get a single row   You are selecting without a where clause  so you probably want to queryForList   The error is probably indicative of the fact that queryForMap wants one row  but you query is retrieving many rows   Check out the docs   There is a queryForList that takes just sql  the return type is  a  List lt Map lt String Object gt  gt      So once you have the results  you can do what you are doing   I would do something like  List results   template queryForList sql    for  Map m   results      m get  userid       m get  username         I ll let you fill in the details  but I would not iterate over keys in this case   I like to explicit about what I am expecting   If you have a User object  and you actually want to load User instances  you can use the queryForList that takes sql and a class type  queryForList String sql  Class lt T gt  elementType    wow Spring has changed a lot since I left Javaland

User · Answer

I know this is really old  but this is the simplest way to query for Map    Simply implement the ResultSetExtractor interface to define what type you want to return  Below is an example of how to use this  You ll be mapping it manually  but for a simple map  it should be straightforward   jdbcTemplate query  select string1 string2 from table where x 1   new ResultSetExtractor lt Map gt          Override     public Map extractData ResultSet rs  throws SQLException DataAccessException           HashMap lt String String gt  mapRet  new HashMap lt String String gt             while rs next                 mapRet put rs getString  string1   rs getString  string2                       return mapRet              This will give you a return type of Map that has multiple rows  however many your query returned  and not a list of Maps  You can view the ResultSetExtractor docs here  http   docs spring io spring-framework docs 2 5 6 api org springframework jdbc core ResultSetExtractor html

User · Answer

To add to  BrianBeech s answer  this is even more trimmed down in java 8   jdbcTemplate query  select string1 string2 from table where x 1    ResultSet rs  - gt        HashMap lt String String gt  results   new HashMap lt  gt         while  rs next              results put rs getString  string1    rs getString  string2               return results

User · Answer

You can do something like this    List lt Map lt String  Object gt  gt  mapList   jdbctemplate queryForList query        return mapList stream   collect Collectors toMap k - gt   Long  k get  userid    k - gt   String  k get  username        Output        1   abc     2   def     3   ghi

[java] How to get Map data using JDBCTemplate.queryForMap

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