I am executing multiple queries concurrently and retrieving the results. But, the queries belong to multiple tables so, when resultset is retrieved, it is difficult to identify that a resultset belong to which table.
Can anyone help here as to how to identify the table names for each query resultset?
I tried below code but table name is blank!!!!
public static void getColumnNames(ResultSet rs) throws SQLException {
if (rs == null) {
return;
}
// get result set meta data
ResultSetMetaData rsMetaData = rs.getMetaData();
int numberOfColumns = rsMetaData.getColumnCount();
// get the column names; column indexes start from 1
for (int i = 1; i < numberOfColumns + 1; i++) {
String columnName = rsMetaData.getColumnName(i);
// Get the name of the column's table name
String tableName = rsMetaData.getTableName(i);
System.out.println("column name=" + columnName + " table=" + tableName + "");
}
}
I am calling this method like this:
jdbcTemplate.query(sql, new ResultSetExtractor<ResultSet>() {
#Override
public ResultSet extractData(ResultSet resultSet) throws SQLException,
DataAccessException {
getColumnNames(resultSet);
return resultSet;
}
});
Please advise, what is done wrong here? :(
You're not doing anything wrong here. The problem is caused by the method itself in connection with your DBMS or your JDBC driver, respectively.
See this doc please. 'table name or "" if not applicable' suggests that in your case the DBMS/driver does not provide the required information, causing the method to return an empty string.
I'm afraid, you'll have to find another way to detect which query the result originated from.
Related
I am working on creating a simple utility that allows our users to execute a pre-selected list of stored procedures that return a simple list result set as a JSON string. The result set varies based on the selected procedure. I am able to get the results easily enough (and pass back as JSON as required), but the results don't include the column names.
The most common answer I found online is to use ResultSetMetaData or NativeQuery, but I couldn't figure out how to extract the metadata or transform the query properly using a StoredProcedureQuery object. How do I get the column names from a StoredProcedureQuery result?
Here is my code:
#SuppressWarnings("unchecked")
public String executeProcedure(String procedure, String jsonData) {
//Set up a call to the stored procedure
StoredProcedureQuery query = entityManager.createStoredProcedureQuery(procedure);
//Register and set the parameters
query.registerStoredProcedureParameter(0, String.class, ParameterMode.IN);
query.setParameter(0, jsonData);
String jsonResults = "[{}]";
try {
//Execute the query and store the results
query.execute();
List list = query.getResultList();
jsonResults = new Gson().toJson(list);
} finally {
try {
//Cleanup
query.unwrap(ProcedureOutputs.class).release();
} catch(Exception e) {
e.printStackTrace();
}
}
return jsonResults;
}
The challenge is to get a ResultSet. In order to list the column names you need a ResultSet to do the following to access metadata. (Column names are metadata)
ResultSetMetaData resultSetMetaData = resultSet.getMetaData();
System.out.println("Column name: "+resultSetMetaData.getColumnName(1));
System.out.println("Column type: "+resultSetMetaData.getColumnTypeName(1));
You can't get ResultSet (or metadata) from javax.persistence.StoredProcedureQuery or from spring-jpa Support JPA 2.1 stored procedures returning result sets
You can with low-level JDBC as follows:
CallableStatement stmnt = conn.prepareCall("{call demoSp(?, ?)}");
stmnt.setString(1, "abcdefg");
ResultSet resultSet1 = stmnt.executeQuery();
resultSet1.getMetaData(); // etc
This issue occurred in jdbc batch insert. I queried from an Oracle datasource, parsed the resultset and then inserted into another Oracle datasource. I have got the connect metadata and printed the current username along with url, both are invalid.
But when it went to batch update, I got the ora-00942 exception. I'm pretty sure all above works fine in database. Has anyone encountered this exception and can you give me some advice?
EDIT:
Ok, I got a table named photos for example in REMOTE_USER and I queried from it. It gave me a resultset, then I parse it after that INSERT it to LOCAL_USER.photos. I did query the LOCAL_USER.photos where I logon in from PL/SQL Developer. The interesting thing was I could do the select command but not the insert. Below is some part of code.
conn = datasource.getConnection(); // notice that it was target datasource
DatabaseMetaData connMetaData = conn.getMetaData();
String userName = connMetaData.getUserName();
resultSet = ds.getResultSet();
ResultSetMetaData metaData = resultSet.getMetaData();
int count = metaData.getColumnCount();
String insertSql = generateInsertSql(count, metaData, userName);
// this was generated through metaData , the output should be
// "insert into LOCAL_USER.photos(col1,col2) values(?,...)"
logger.error("insert clause is {}", insertSql);
ps = conn.prepareStatement(insertSql);
conn.setAutoCommit(false);
while (resultSet.next()) { // this was the original datasource
stageTotalNum++;
for (int i = 1; i <= count; i++) {
Object object = resultSet.getObject(i);
dealClobColumn(ps, i, object);
}
ps.addBatch();
if (stageTotalNum % 500L == 0L) {
ps.executeBatch(); // throws batchupdateexception.
ps.clearBatch();
conn.commit();
}
}
ps.executeBatch();
conn.commit();
It should be the blob type column which I didn't handle it the right way.
First I queried from original datasource then got the blob column of the resultset by
conn.getObject(index) . Next I insert the blob column into target datasource by conn.setObject. Of course that way wasn't working at all, so I changed to the following:
conn.setBlob(rs.getBlob(index)).
Although it worked fine in my own environemnt, but when the application ran in remote server, it kept annoying about the 'table or view does not exists'.The third version is:
conn.setBinaryStream(rs.getBlob(index).getBinaryStream());
Ok, this time it worked both my pc and remote server. Thanks to #codeLover's advice and link, it really hepled me and saved my time. Appreciated it!
I am fairly new to spring ,I am looking to check if a certain email id exists in database or not , using Spring Jdbc Template ,I looked here but could'nt find the proper answer .I am looking something like ,SELECT count(*) from table where email=?
Any help will be appreciated.
You can do something as below if you are using jdbctemplate and new version of spring
private boolean isEmailIdExists(String email) {
String sql = "SELECT count(*) FROM table WHERE email = ?";
int count = jdbcTemplate.queryForObject(sql, new Object[] { email }, Integer.class);
return count > 0;
}
queryForObject method of jdbcTemplate accepts the sql query as the first parameter, second argument is an array of objects for the sql query place holders and the third argument is the expected return value from the sql query.
In this case we only have one place holder and hence I gave the second argument as new Object[] { email } and the result we are expecting is a count which is a Integer and hence I gave it as Integer.class
I kind of got this answer from https://www.mkyong.com/spring/jdbctemplate-queryforint-is-deprecated/
You can go through it if you are interested.
private boolean isEmailIdExists(String email) {
return jdbcTemplate.queryForObject("SELECT EXISTS(SELECT FROM table WHERE email = ?)", Boolean.class, email);
}
http://www.postgresqltutorial.com/postgresql-exists/
servlets, oracle SQL developer .. i want to select data from database but accoeding to user inputs .. here is my code
public ResultSet f_items(Connection conn,String price) throws SQLException {
String query = "select * from items where price=? ";
Statement st=conn.createStatement();
ResultSet set=st.executeQuery(query);
return set;
}
the price is a column in the table ... but this code gives me an SQL exception which is
: ORA-01008: not all variables bound
any help ??
You do not set the expected price on the statement. It should look sth. like this:
....
String query = "select * from items where price='" + price + "'";
ResultSet set=st.executeQuery(query);
EDIT: like Multisync suggested, but with an explanation :)
String query = "select * from items where price=? ";
PreparedStatement st=conn.prepareStatement(query);
st.setString(1, price);
ResultSet set=st.executeQuery(query);
Why is using a prepared statement better?
concatenating user input into DB queries is a recipe for disaster, known as SQL injection.
methods of PreparedStatement like setString will escape the string value for you, preventing SQL injection.
public ResultSet f_items(Connection conn,String price) throws SQLException {
String query = "select * from items where price=? ";
PreparedStatement st=conn.prepareStatement(query);
st.setString(1, price);
ResultSet set=st.executeQuery(query);
return set;
}
Is there any way I can get resultset object from one of jdbctemplate query methods?
I have a code like
List<ResultSet> rsList = template.query(finalQuery, new RowMapper<ResultSet>() {
public ResultSet mapRow(ResultSet rs, int rowNum) throws SQLException {
return rs;
}
}
);
I wanted to execute my sql statement stored in finalQuery String and get the resultset. The query is a complex join on 6 to 7 tables and I am select 4-5 columns from each table and wanted to get the metadata of those columns to transform data types and data to downstream systems.
If it is a simple query and I am fetching form only one table I can use RowMapper#mapRow and inside that maprow method i can call ResultsetExtractor.extractData to get list of results; but in this case I have complex joins in my query and I am trying to get resultset Object and from that resultset metadata...
The above code is not good because for each result it will return same resultset object and I dont want to store them in list ...
Once more thing is if maprow is called for each result from my query will JDBCTemplate close the rs and connection even though my list has reference to RS object?
Is there any simple method like jdbcTemplate.queryForResultSet(sql) ?
Now I have implemented my own ResultSet Extractor to process and insert data into downstream systems
sourceJdbcTemplate.query(finalQuery, new CustomResultSetProcessor(targetTable, targetJdbcTemplate));
This CustomResultSetProcessor implements ResultSetExtractor and in extractData method I am calling 3 different methods 1 is get ColumnTypes form rs.getMetaData() and second is getColumnTypes of target metadata by running
SELECT NAME, COLTYPE, TBNAME FROM SYSIBM.SYSCOLUMNS WHERE TBNAME ='TABLENAME' AND TABCREATOR='TABLE CREATOR'
and in 3rd method I am building the insert statement (prepared) form target columntypes and finally calling that using
new BatchPreparedStatementSetter()
{
#Override
public void setValues(PreparedStatement insertStmt, int i) throws SQLException{} }
Hope this helps to others...
Note that the whole point of Spring JDBC Template is that it automatically closes all resources, including ResultSet, after execution of callback method. Therefore it would be better to extract necessary data inside a callback method and allow Spring to close the ResultSet after it.
If result of data extraction is not a List, you can use ResultSetExtractor instead of RowMapper:
SomeComplexResult r = template.query(finalQuery,
new ResultSetExtractor<SomeComplexResult>() {
public SomeResult extractData(ResultSet) {
// do complex processing of ResultSet and return its result as SomeComplexResult
}
});
Something like this would also work:
Connection con = DataSourceUtils.getConnection(dataSource); // your datasource
Statement s = con.createStatement();
ResultSet rs = s.executeQuery(query); // your query
ResultSetMetaData rsmd = rs.getMetaData();
Although I agree with #axtavt that ResultSetExtractor is preferred in Spring environment, it does force you to execute the query.
The code below does not require you to do so, so that the client code is not required to provide the actual arguments for the query parameters:
public SomeResult getMetadata(String querySql) throws SQLException {
Assert.hasText(querySql);
DataSource ds = jdbcTemplate.getDataSource();
Connection con = null;
PreparedStatement ps = null;
try {
con = DataSourceUtils.getConnection(ds);
ps = con.prepareStatement(querySql);
ResultSetMetaData md = ps.getMetaData(); //<-- the query is compiled, but not executed
return processMetadata(md);
} finally {
JdbcUtils.closeStatement(ps);
DataSourceUtils.releaseConnection(con, ds);
}
}