I have a wierd behavior in a Java application.
It issues simple queries and modifications to a remote MySQL database. I found that queries, run by executeQuery() work just fine, but inserts or delete to the database run through executeUpdate() will fail.
Ruling out the first thing that comes to mind: the user the app connects with has correct privilledges set up, as the same INSERT run from the same machine, but in DBeaver, will produce the desired modification.
Some code:
Connection creation
Class.forName("com.mysql.jdbc.Driver");
connection = DriverManager.getConnection(url, user, pass);
Problematic part:
Statement parentIdStatement = connection.createStatement();
String parentQuery = String.format(ProcessDAO.GET_PARENT_ID, parentName);
if (DEBUG_SQL) {
plugin.getLogger().log(Level.INFO, parentQuery);
}
ResultSet result = parentIdStatement.executeQuery(parentQuery);
result.first();
parentId = result.getInt(1);
if (DEBUG_SQL) {
plugin.getLogger().log(Level.INFO, parentId.toString()); // works, expected value
}
Statement createContainerStatement = connection.createStatement();
String containerQuery = String.format(ContainerDAO.CREATE_CONTAINER, parentId, myName);
if (DEBUG_SQL) {
plugin.getLogger().log(Level.INFO, containerQuery); // works when issued through DBeaver
}
createContainerStatement.executeUpdate(containerQuery); // does nothing
"DAOs":
ProcessDAO.GET_PARENT_ID = "SELECT id FROM mon_process WHERE proc_name = '%1$s'";
ContainerDAO.CREATE_CONTAINER = "INSERT INTO mon_container (cont_name, proc_id, cont_expiry, cont_size) VALUES ('%2$s', %1$d, CURRENT_TIMESTAMP(), NULL)";
I suspect this might have to do with my usage of Statement and Connection.
This being a lightweight lightly-used app, I went to simplicity, so no framework, and no specific isntructions regarding transactions or commits.
So, in the end, this code was just fine. It worked today.
To answer the question: where to look first in a similar case (SELECT works but UPDATE / INSERT / DELETE does not)
If rights are not the problem, then there is probably a lock on the table you try to modify. In my case, someone left with an uncommited transaction open.
Proper SQL exceptions logging (which was suboptimal in my case) will help you figure it out.
Related
Before I explain my problem I would like to say that I know the basics of JDBC but not really used to it.
I am using an updatable result set to hold data from 2 different tables, as in the following sample code:
searchQry = "SELECT ct.CustomerName, ct.Email, ct.PhoneNo, ot.ItemName
FROM CUSTOMER_TABLE ct JOIN ORDER_Table ot
ON ct.OrderID = ot.OrderID";
prestmt = dbcon.prepareStatement(searchQry, ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
uprs = prestmt.executeQuery();
uprs.updateLong("ut.PhoneNo", 7240987456L);
uprs.updateString("otItemName", "GTA5");
uprs.updateRow();
I would like to know if I will update the database from somewhere else (not using the same result set object) while the result set, upsr, connected to the database, whether uprs will get updated with it or it will throw an error or it will go with the old data itself. Sorry if it a newbie question but I can't really test that on my DB without knowing the outcomes and safe measures.
Please, suggest me if there is any better way to update the underlining db along with the data in the ResultSet without having any transaction issues when changing from different places.
Using:
Oracle Database for JDBC connection.
I'm starting with SQL and trying to mix it with Java app. I have table ZAMESTNANEC containing 6 rows.
When I issue the command delete from ZAMESTNANEC where ID = 7; in SQL it will delete in no time. A few milliseconds. But when I use this in my Java app, the app will freeze in processing. I waited for 4 minutes and nothing happened (and due to its working state I can't do anything else). Oh and the row wasn't deleted.
I read this topic about deleting but it didn't help me much. In fact it didn't help me at all.
oracle delete query taking too much time
I tried to debug it but it's frozen on this command. I don't understand why in SQL it works fine and in Java app it doesn't. Other commands like SELECT works fine.
JDBC here - http://pastebin.com/BRh06yc8
Code from button here
private void jButtonOdeberZamActionPerformed(java.awt.event.ActionEvent evt) {
try{
OracleConnector.setUpConnection("xxxxxxxx", 1521, "ee11",
"NAME", "PASSWORD");
conn = OracleConnector.getConnection();
stmt = conn.createStatement();
stmt.executeQuery("delete from ZAMESTNANEC where ID = 7");
} catch(SQLException ex){
System.out.println(ex);
}
executeQuery should be used for queries that are expected to return results. Try executeUpdate instead and see if that helps. It could be that your app is waiting to receive results which never come back. By Tom H
Thank you Tom.
I have a java servlet application and I'm using a prepared query to update a record in a SQL Server Database table.
Lets say I want to execute UPDATE MyTable SET name = 'test' WHERE id = '10'. (Yes, id is a varchar)
I used the following code to make this happen:
PreparedStatement pstmt = con.prepareStatement("UPDATE MyTable SET name = ? WHERE id = ?");
pstmt.setString(1, getName() );
pstmt.setString(2, getID() );
pstmt.executeUpdate();
I found out that while I was running a JMeter script to simulate 2 users, this statement causes a deadlock in my database.
I wanted to check what my values were in the SQL Profiler so I used the following code, so I could check the values.
String query = String.format("UPDATE MyTable SET name = '%s' WHERE id = '%s' ", getName(), getID() );
PreparedStatement pstmt = con.prepareStatement(query);
pstmt.executeUpdate();
Suddenly my deadlock was gone! It's a shame the last approach is vulnerable to SQL injection.
Is there somebody who can tell me what is going on and/or how to fix it?
Ok I finally found the problem and solution to my problem.
It seemed that the combination of the jTDS JDBC driver with MSSQL was the 'problem'.
This article explained my situation exactly. And with the help of this FAQ I was able to set the datasource to the right configuration.
From what I understand:
If you have statement that uses a String-like index (Like in my situation), the table performs an index SCAN instead of an index SEEK. This causes the whole table to be locked and vulnerable to deadlocks.
I hope this will help other people too.
I have a big but INTERMITTENT problem with a bug in Oracle 10g when we call some SQL within a Java web application. We can't quickly patch or upgrade to 11g - which seems to be the first 'stupid' oracle support response. There is a work around, but I am having trouble doing this within PreparedStatements within my Java code.
The actual error is:
ORA-00600: internal error code, arguments: [kcblasm_1]
The bug is: Oracle Bug 12419392
The work around is running
alter session set "_hash_join_enabled" = FALSE;
before we run our bug-inducing SQL. However, traditionally a PreparedStatement takes in one single piece of SQL:
PreparedStatement stmt = con.prepareSelect("sql statement2");
Is it possible to have one PreparedStatement call that looks like this:
PreparedStatement stmt = con.prepareSelect("sql statement1; sql statement2;");
Or is this possible just by running a series of sequential PreparedStatements one after the other?
Not the best time to be getting this with Xmas looming and reduced support etc. etc., so I really hope someone can help. Thanks.
Edit: #jonearles asked for the code, so here it is, if it's on any use. Probably very specific to our project, but someone might spot the glaring bug-inducing issue:
SELECT DISTINCT qm.validator_id,
qm.QM_ID,
u.EMAIL,
qm.creation_dt,
qm.emailed,
qm.valid,
qm.resolved,
qm.new_obs_id,
o.*,
nests.*,
s.*,
l.*,
latc.TENKM
FROM query_man qm,
obs o,
obs_aux_aon nests,
sub s,
location l,
l_atlas_tetrad_coverage latc,
users u
WHERE qm.OBS_ID = o.OBS_ID
AND o.SUB_ID = s.SUB_ID
AND u.user_id = qm.user_id
AND o.obs_id = nests.obs_id(+)
AND s.LOC_ID = l.LOC_ID
AND latc.ATLAS_REGION = 'NKNE'
AND (LENGTH (l.gridref) = 6
AND (SUBSTR(l.gridref,1,3)
|| SUBSTR(l.gridref,5,1)) = latc.TENKM
OR LENGTH (l.gridref) = 4
AND l.gridref = latc.TENKM)
AND qm.RESOLVED IS NULL
ORDER BY latc.tenkm,
l.tetrad
OK. The answer to my primary question is NO, you can't create a PreparedStatement like so:
PreparedStatement stmt = con.prepareSelect("sql statement1; sql statement2;");
Running individual statements to alter session temporarily for one bit of SQL did work, but agreed seems awful and also unacceptably slowed response. Options seem to be patch or upgrade, or look into the no_use_hash hint (which I think will be slow too). Will look at code.
I am using a MySQL DB and a Java JDBC client to access it.
I have a Table that contains session information. Each session is associated with a SessionToken. This token is a Base64 encoded String of a Hash of some of the session values. It should be unique. And is defined as varchar(50) in the db.
When I try to lookup a session by its token I query the database using an sql statement like this:
select SessionId, ClientIP, PersonId, LastAccessTime, SessionCreateTime from InkaSession where SessionToken like 'exK/Xw0imW/qOtN39uw5bddeeMg='
I have a UnitTest that tests this functionality, and it consistently fails, because the query does not return any Session, even tough, I have just written the session to the DB.
My Unit test does the following:
Create Connection via DriverManager.getConnection
Add a session via Sql Insert query
close the connection
create Connection via DriverManager.getConnection
look for the session via sql select
unit test fails, because nothing found
When I step through this UnitTest with the debugger and copy past the select sql that is about to be sent to the db into a mysql command line, it works fine, and I get the session row back.
I also tried to retrive an older session from the db by asking for an older SessionToken. This works fine as well. It only fails, if I ask for the SessionToken immediately after I inserted it.
All connections are on AutoCommit. Nevertheless I tried to set the Transaction Level to "Read Uncommited". This did not work either.
Has anyone any further suggestions?
This is typically caused by the connection not being committed between insert and select.
Did you basically do the following?
statement.executeUpdate("INSERT INTO session (...) VALUES (...)");
connection.commit();
resultSet = statement.executeQuery("SELECT ... FROM session WHERE ...");
Edit I tried the following SSCCE on MySQL 5.1.30 with Connector/J 5.1.7:
public static void main(String[] args) throws Exception {
Class.forName("com.mysql.jdbc.Driver");
Connection connection = null;
Statement statement = null;
ResultSet resultSet = null;
try {
connection = DriverManager.getConnection("jdbc:mysql://localhost/javabase", "root", null);
statement = connection.createStatement();
statement.executeUpdate("INSERT INTO foo (foo) VALUES ('foo')");
resultSet = statement.executeQuery("SELECT id FROM foo WHERE foo = 'foo'");
if (resultSet.next()) {
System.out.println(resultSet.getLong("id"));
} else {
System.out.println("Not inserted?");
}
} finally {
SQLUtil.close(connection, statement, resultSet);
}
}
Works flawlessly. Maybe an issue with your JDBC driver. Try upgrading.
Solved: The two token strings where not identical. One of them had a couple of Zero bytes at the end. (Due to the encrypting and decrypting and padding...) The two strings where visually identical, but MySQL and Java both said, they where not. (And they where right as usual)