Jdbctemplate query for string: EmptyResultDataAccessException: Incorrect result size: expected 1, actual 0

问题:

I am using Jdbctemplate to retrieve a single String value from the db. Here is my method.

    public String test() {         String cert=null;         String sql = "select ID_NMB_SRZ from codb_owner.TR_LTM_SLS_RTN               where id_str_rt = '999' and ID_NMB_SRZ = '60230009999999'";         cert = (String) jdbc.queryForObject(sql, String.class);          return cert;     } 

In my scenario it is complete possible to NOT get a hit on my query so my question is how do I get around the following error message.

EmptyResultDataAccessException: Incorrect result size: expected 1, actual 0 

It would seem to me that I should just get back a null instead of throwing an exception. How can I fix this? Thanks in advance.

回答1:

In JdbcTemplate , queryForInt, queryForLong, queryForObject all such methods expects that executed query will return one and only one row. If you get no rows or more than one row that will result in IncorrectResultSizeDataAccessException . Now the correct way is not to catch this exception or EmptyResultDataAccessException, but make sure the query you are using should return only one row. If at all it is not possible then use query method instead.

List strLst  = getJdbcTemplate().query(sql,new RowMapper {    public Object mapRow(ResultSet rs, int rowNum) throws SQLException {         return rs.getString(1);   }  });  if ( strLst.isEmpty() ){   return null; }else if ( strLst.size() == 1 ) { // list contains exactly 1 element   return strLst.get(0); }else{  // list contains more than 1 elements   //your wish, you can either throw the exception or return 1st element.     } 

回答2:

You may also use a ResultSetExtractor instead of a RowMapper. Both are just as easy as one another, the only difference is you call ResultSet.next().

public String test() {     String sql = "select ID_NMB_SRZ from codb_owner.TR_LTM_SLS_RTN "                  + " where id_str_rt = '999' and ID_NMB_SRZ = '60230009999999'";     return jdbc.query(sql, new ResultSetExtractor() {         @Override         public String extractData(ResultSet rs) throws SQLException,                                                        DataAccessException {             return rs.next() ? rs.getString("ID_NMB_SRZ") : null;         }     }); } 

The ResultSetExtractor has the added benefit that you can handle all cases where there are more than one row or no rows returned.

UPDATE: Several years on and I have a few tricks to share. JdbcTemplate works superbly with java 8 lambdas which the following examples are designed for but you can quite easily use a static class to achieve the same.

While the question is about simple types, these examples serve as a guide for the common case of extracting domain objects.

First off. Let's suppose that you have an account object with two properties for simplicity Account(Long id, String name). You would likely wish to have a RowMapper for this domain object.

private static final RowMapper MAPPER_ACCOUNT =         (rs, i) -> new Account(rs.getLong("ID"),                                rs.getString("NAME")); 

You may now use this mapper directly within a method to map Account domain objects from a query (jt is a JdbcTemplate instance).

public List getAccounts() {     return jt.query(SELECT_ACCOUNT, MAPPER_ACCOUNT); } 

Great, but now we want our original problem and we use my original solution reusing the RowMapper to perform the mapping for us.

public Account getAccount(long id) {     return jt.query(             SELECT_ACCOUNT,             rs -> rs.next() ? MAPPER_ACCOUNT.mapRow(rs, 1) : null,             id); } 

Great, but this is a pattern you may and will wish to repeat. So you can create a generic factory method to create a new ResultSetExtractor for the task.

public static  ResultSetExtractor singletonExtractor(         RowMapper extends T> mapper) {     return rs -> rs.next() ? mapper.mapRow(rs, 1) : null; } 

Creating a ResultSetExtractor now becomes trivial.

private static final ResultSetExtractor EXTRACTOR_ACCOUNT =         nullableExtractor(MAPPER_ACCOUNT);  public Account getAccount(long id) {     return jt.query(SELECT_ACCOUNT, EXTRACTOR_ACCOUNT, id); } 

I hope this helps to show that you can now quite easily combine parts in a powerful way to make your domain simpler.

UPDATE 2: Combine with an Optional for optional values instead of null.

public static  ResultSetExtractor> singletonOptionalExtractor(         RowMapper extends T> mapper) {     return rs -> rs.next() ? Optional.of(mapper.mapRow(rs, 1)) : Optional.empty(); } 

Which now when used could have the following:

private static final ResultSetExtractor> EXTRACTOR_DISCOUNT =         nullableOptionalExtractor(MAPPER_DISCOUNT);  public double getDiscount(long accountId) {     return jt.query(SELECT_DISCOUNT, EXTRACTOR_DISCOUNT, accountId)             .orElse(0.0); } 

回答3:

That's not a good solution because you're relying on exceptions for control flow. In your solution it's normal to get exceptions, it's normal to have them in the log.

public String test() {     String sql = "select ID_NMB_SRZ from codb_owner.TR_LTM_SLS_RTN where id_str_rt = '999' and ID_NMB_SRZ = '60230009999999'";     List certs = jdbc.queryForList(sql, String.class);      if (certs.isEmpty()) {         return null;     } else {         return certs.get(0);     } } 

回答4:

Actually, You can play with JdbcTemplate and customize your own method as you prefer. My suggestion is to make something like this:

public String test() {     String cert = null;     String sql = "select ID_NMB_SRZ from codb_owner.TR_LTM_SLS_RTN         where id_str_rt = '999' and ID_NMB_SRZ = '60230009999999'";     ArrayList certList = (ArrayList) jdbc.query(         sql, new RowMapperResultSetExtractor(new UserMapper()));     cert =  DataAccessUtils.singleResult(certList);      return cert; } 

It works as the original jdbc.queryForObject, but without throw new EmptyResultDataAccessException when size == 0.

回答5:

Since returning a null when there is no data is something I want to do often when using queryForObject I have found it useful to extend JdbcTemplate and add a queryForNullableObject method similar to below.

public class JdbcTemplateExtended extends JdbcTemplate {      public JdbcTemplateExtended(DataSource datasource){         super(datasource);     }      public  T queryForNullableObject(String sql, RowMapper rowMapper) throws DataAccessException {         List results = query(sql, rowMapper);          if (results == null || results.isEmpty()) {             return null;         }         else if (results.size() > 1) {             throw new IncorrectResultSizeDataAccessException(1, results.size());         }         else{             return results.iterator().next();         }     }      public  T queryForNullableObject(String sql, Class requiredType) throws DataAccessException {         return queryForObject(sql, getSingleColumnRowMapper(requiredType));     }  } 

You can now use this in your code the same way you used queryForObject

String result = queryForNullableObject(queryString, String.class); 

I would be interested to know if anyone else thinks this is a good idea?

回答6:

Ok, I figured it out. I just wrapped it in a try catch and send back null.

    public String test() {             String cert=null;             String sql = "select ID_NMB_SRZ from codb_owner.TR_LTM_SLS_RTN                       where id_str_rt = '999' and ID_NMB_SRZ = '60230009999999'";             try {                 Object o = (String) jdbc.queryForObject(sql, String.class);                 cert = (String) o;             } catch (EmptyResultDataAccessException e) {                 e.printStackTrace();             }             return cert;     } 

回答7:

You could use a group function so that your query always returns a result. ie

MIN(ID_NMB_SRZ) 

回答8:

In Postgres, you can make almost any single value query return a value or null by wrapping it:

SELECT (SELECT ) AS value 

and hence avoid complexity in the caller.

回答9:

Since getJdbcTemplate().queryForMap expects minimum size of one but when it returns null it shows EmptyResultDataAccesso fix dis when can use below logic

Map loginMap =null; try{     loginMap = getJdbcTemplate().queryForMap(sql, new Object[] {CustomerLogInInfo.getCustLogInEmail()}); } catch(EmptyResultDataAccessException ex){     System.out.println("Exception.......");     loginMap =null; } if(loginMap==null || loginMap.isEmpty()){     return null; } else{     return loginMap; } 

回答10:

I dealt with this before & had posted in the spring forums.

http://forum.spring.io/forum/spring-projects/data/123129-frustrated-with-emptyresultdataaccessexception

The advice we received was to use a type of SQlQuery. Here's an example of what we did when trying to get a value out of a DB that might not be there.

@Component public class FindID extends MappingSqlQuery {          @Autowired         public void setDataSource(DataSource dataSource) {                  String sql = "Select id from address where id = ?";                  super.setDataSource(dataSource);                  super.declareParameter(new SqlParameter(Types.VARCHAR));                  super.setSql(sql);                  compile();         }          @Override         protected Long mapRow(ResultSet rs, int rowNum) throws SQLException {                 return rs.getLong(1);         } 

In the DAO then we just call...

Long id = findID.findObject(id); 

Not clear on performance, but it works and is neat.

回答11:

For Byron, you can try this..

public String test(){                 String sql = "select ID_NMB_SRZ from codb_owner.TR_LTM_SLS_RTN                       where id_str_rt = '999' and ID_NMB_SRZ = '60230009999999'";                 List li = jdbcTemplate.queryForList(sql,String.class);                 return li.get(0).toString();         } 

回答12:

to make

    jdbcTemplate.queryForList(sql, String.class) 

work, make sure your jdbcTemplate is of type

    org.springframework.jdbc.core.JdbcTemplate 

回答13:

I just catch this "EmptyResultDataAccessException"

public Myclass findOne(String id){     try {         Myclass m = this.jdbcTemplate.queryForObject(                 "SELECT * FROM tb_t WHERE id = ?",                 new Object[]{id},                 new RowMapper() {                     public Myclass mapRow(ResultSet rs, int rowNum) throws SQLException {                         Myclass m = new Myclass();                         m.setName(rs.getString("name"));                         return m;                     }                 });         return m;     } catch (EmptyResultDataAccessException e) { // result.size() == 0;         return null;     } } 

then you can check:

if(m == null){     // insert operation. }else{     // update operation. } 

回答14:

We can use query instead of queryForObject, major difference between query and queryForObject is that query return list of Object(based on Row mapper return type) and that list can be empty if no data is received from database while queryForObject always expect only single object be fetched from db neither null nor multiple rows and in case if result is empty then queryForObject throws EmptyResultDataAccessException, I had written one code using query that will overcome the problem of EmptyResultDataAccessException in case of null result.

----------   public UserInfo getUserInfo(String username, String password) {       String sql = "SELECT firstname, lastname,address,city FROM users WHERE id=? and pass=?";       List userInfoList = jdbcTemplate.query(sql, new Object[] { username, password },               new RowMapper() {                   public UserInfo mapRow(ResultSet rs, int rowNum) throws SQLException {                       UserInfo user = new UserInfo();                       user.setFirstName(rs.getString("firstname"));                       user.setLastName(rs.getString("lastname"));                       user.setAddress(rs.getString("address"));                       user.setCity(rs.getString("city"));                        return user;                   }               });        if (userInfoList.isEmpty()) {           return null;       } else {           return userInfoList.get(0);       }   } 

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