I wonder how come this error is thrown while hosting my project in APP ENGINE, I have added lots of logging just for analysis sake. When I use the com.mysql.jdbc.Driver using ip from my local it works. Kindly help !!
String name = "Vinodh";
String url = null;
try {
Class.forName("com.mysql.jdbc.GoogleDriver");
url = "jdbc:google:mysql://xxxxxxx:xxxxxx/vinodh?user=root&password=xxxxxx";
// Statements allow to issue SQL queries to the database
log.info("Initiate Connection");
Connection conn = DriverManager.getConnection(url);
log.info("Got Connection");
Statement statement = conn.createStatement();
// Result set get the result of the SQL query
ResultSet resultSet = statement
.executeQuery("select * from Family");
log.info("Entering While");
while(resultSet.next()){
log.info("Entered While");
String test = resultSet.getString("Name");
System.out.println(test);
name = test+test+test;
}
As shwown in this tutorial, during development you should use the normal mysql driver and only appengine use the Google mysql driver
if (SystemProperty.environment.value() ==
SystemProperty.Environment.Value.Production) {
// Load the class that provides the new "jdbc:google:mysql://" prefix.
Class.forName("com.mysql.jdbc.GoogleDriver");
url = "jdbc:google:mysql://your-project-id:your-instance-name/guestbook?user=root";
} else {
// Local MySQL instance to use during development.
Class.forName("com.mysql.jdbc.Driver");
url = "jdbc:mysql://127.0.0.1:3306/guestbook?user=root";
}
Also double check that you have enabled MySQL Connector/J for your application (it's not done by default)
https://developers.google.com/appengine/docs/java/cloud-sql/#enable_connector_j
<?xml version="1.0" encoding="utf-8"?>
<appengine-web-app xmlns="http://appengine.google.com/ns/1.0">
...
<use-google-connector-j>true</use-google-connector-j>
</appengine-web-app>
Appearently they removed this quietly. It's not even in the docs of appengine-web.xml anymore.
Use the standard com.mysql.jdbc.Driver but update your JDBC url for:
jdbc:mysql://google/[your-db-schema]
?user=root
&password=[your-db-passord]
&socketFactory=com.google.cloud.sql.mysql.SocketFactory
&cloudSqlInstance=[your-db-project-id]:[your-db-region]:[your-db-intance]
Add also to your gradle:
dependencies {
...
implementation("mysql:mysql-connector-java:8.0.29")
implementation("com.google.cloud.sql:mysql-socket-factory-connector-j-8:1.5.0")
}
Note the "google" in the URI. There's no place in the docs saying that you need it, but you have to.
Github official page guide
Related
I am trying to move data from a SPARQL endpoint to a JSONObject. Using RDF4J.
RDF4J documentation does not address this directly (some info about using endpoints, less about converting to JSON, and nothing where these two cases meet up).
Sofar I have:
SPARQLRepository repo = new SPARQLRepository(<My Endpoint>);
Map<String, String> headers = new HashMap<String, String>();
headers.put("Accept", "SPARQL/JSON");
repo.setAdditionalHttpHeaders(headers);
try (RepositoryConnection conn = repo.getConnection())
{
String queryString = "SELECT * WHERE {GRAPH <urn:x-evn-master:mwadata> {?s ?p ?o}}";
GraphQuery query = conn.prepareGraphQuery(queryString);
debug("Mark 2");
try (GraphQueryResult result = query.evaluate())
this fails because "Server responded with an unsupported file format: application/sparql-results+json"
I figured a SPARQLGraphQuery should take the place of GraphQuery, but RepositoryConnection does not have a relevant prepare statement.
If I exchange
try (RepositoryConnection conn = repo.getConnection())
with
try (SPARQLConnection conn = (SPARQLConnection)repo.getConnection())
I run into the problem that SPARQLConnection does not generate a SPARQLGraphQuery. The closest I can get is:
SPARQLGraphQuery query = (SPARQLGraphQuery)conn.prepareQuery(QueryLanguage.SPARQL, queryString);
which gives a runtime error as these types cannot be cast to eachother.
I do not know how to proceed from here. Any help or advise much appreciated. Thank you
this fails because "Server responded with an unsupported file format: application/sparql-results+json"
In RDF4J, SPARQL SELECT queries are tuple queries, so named because each result is a set of bindings, which are tuples of the form (name, value). In contrast, CONSTRUCT (and DESCRIBE) queries are graph queries, so called because their result is a graph, that is, a collection of RDF statements.
Furthermore, setting additional headers for the response format as you have done here is not necessary (except in rare circumstances), the RDF4J client handles this for you automatically, based on the registered set of parsers.
So, in short, simplify your code as follows:
SPARQLRepository repo = new SPARQLRepository(<My Endpoint>);
try (RepositoryConnection conn = repo.getConnection()) {
String queryString = "SELECT * WHERE {GRAPH <urn:x-evn-master:mwadata> {?s ?p ?o}}";
TupleQuery query = conn.prepareTupleQuery(queryString);
debug("Mark 2");
try (TupleQueryResult result = query.evaluate()) {
...
}
}
If you want to write the result of the query in JSON format, you could use a TupleQueryResultHandler, for example the SPARQLResultsJSONWriter, as follows:
SPARQLRepository repo = new SPARQLRepository(<My Endpoint>);
try (RepositoryConnection conn = repo.getConnection()) {
String queryString = "SELECT * WHERE {GRAPH <urn:x-evn-master:mwadata> {?s ?p ?o}}";
TupleQuery query = conn.prepareTupleQuery(queryString);
query.evaluate(new SPARQLResultsJSONWriter(System.out));
}
This will write the result of the query (in this example to standard output) using the SPARQL Query Results JSON format. If you have a non-standard format in mind, you could of course also create your own TupleQueryResultHandler implementation.
For more details on the various ways in which you can process the result (including iterating, streaming, adding to a List, or just directly sending to a result handler), see the documentation on querying a repository. As an aside, the javadoc on the RDF4J APIs is pretty extensive too, so if your Java editing environment has support for displaying that, I'd advise you to make use of it.
Similar to the question answered here https://stackoverflow.com/a/42932812/1321510 we need to execute a raw sql query. For the query we don't have any db context model (so any .FromSql answers won't work for us). However we need to execute it within an existing transaction (created with context.Database.BeginTransaction()). All solutions found on SO do not work with existing transactions.
Example:
var connection = context.Database.GetDbConnection();
using (var command = connection.CreateCommand())
{
command.CommandText = sql;
command.Transaction = context.Database.CurrentTransaction.GetDbTransaction();
var executeReader = command.ExecuteReader();
var values = new object[executeReader.FieldCount];
if (!executeReader.Read())
{
return values;
}
executeReader.GetValues(values);
return values;
}
}
Commiting the transaction then throws System.InvalidOperationException: 'This MySqlConnection is already in use. See https://fl.vu/mysql-conn-reuse'.
The provided link in the exception doesn't seem helpful at all, since we're neither using async nor using the connection whilst reading from it.
We're using Pomelo.EntityFrameworkCore.MySql as the database connector.
i have the following code which has been getting me data from flat files. but now all of a sudden i am getting this error
System.Data.OleDb.OleDbException: Invalid path or file name
but the code hasnt changed it worked for months,im not sure what went wrong.
System.Web.Script.Serialization.JavaScriptSerializer json = new System.Web.Script.Serialization.JavaScriptSerializer();
string jsonText;
System.Collections.Generic.List<object> objList = new List<object>();
string strConn = #"Provider=vfpoledb;Data Source=\\10.0.0.0\wwwroot\apps\assembly\FlatDatabaseDbfs\vt_Flat.dbf;Collating Sequence=machine;";
using (System.Data.OleDb.OleDbConnection conn = new System.Data.OleDb.OleDbConnection(strConn))
{
System.Data.OleDb.OleDbCommand cmddbf = new System.Data.OleDb.OleDbCommand();
cmddbf.Connection = conn;
conn.Open();
cmddbf.CommandText = "select * from vt_Flat";
var dr = cmddbf.ExecuteReader();
while (dr.Read())
{
objList.Add(new
{
Code = (dr["dp_code"].ToString().Trim()),
});
};
}
var filteredList = objList.Where(obj => ((dynamic)obj).Status == (Request.QueryString["Status"] ?? "") && ((dynamic)obj).DepCode == (Request.QueryString["Code"] ?? ""));
jsonText = json.Serialize(filteredList);
Response.Write(jsonText);
}
is there something wrong with iis permissions?
Aside from the connection having to point to the PATH as already noted by Oleg, in the C# instances of OleDbConnection I have done in the past, the connection string uses
Provider=VFPOLEDB.1
Don't know if it is case/sensitive issue and the ".1" which is also part of the provider string.
Once you have a valid connection to the PATH, then your query can query from any table within the path location. So if you had 2+ files, and needed to join them, you would do so with a standard query / join. In your case, your command text is only "select *" since you changed your original connection that included the table. Change the command text to
"select * from vt_Flat"
OTHER CONSIDERATIONS
Is this being run from some web service project? If so, THAT could be the basis. You as a developer testing are running with your permissions / access. If running as a web server, the WEB-based user account may not have permissions to the folder to process / work with the data.
Check the folder of your production data to ALLOW the web user if so running. If that doesn't work, set permissions on the folder to EVERYBODY (only for testing/confirmation purposes only). See if that is the problem.
Also, from the Provider connection, did you try with it as all upper case VFPOLEDB.1?
Use path instead of file name, e.g.:
Data Source=\\10.0.0.0\wwwroot\apps\assembly\FlatDatabaseDbfs\;
Edit: I solved my problem but if you have anything to add please do. Thanks
Note: I did not create the DB it was created by Wordpress hosted on GoDaddy with my site
I have a MySql Database called "wordpress" (for clarity). I want to be able to grab the most recent post from my blog and show it on the landing page for my url.
So my thought is this: connect to the MySql DB, run a query to grab the most recent post, display the post.
I built a class to handle the connection and process the request:
public class DAL
{
private string connectionString = "DRIVER={MySQL ODBC 3.51 Driver}; SERVER=[server here]; PORT=[port]; DATABASE=wordpress;
USER=[user name here]; PASSWORD=[password here];";
private OdbcConnection blogConnection;
public DAL()
{
blogConnection = new OdbcConnection(connectionString);
}
public String[] GetRecentPost()
{
string queryString = "SELECT * FROM RecentPost";
String[] recentPost = new String[3];
//ODBC
blogConnection.Open();
OdbcCommand MySqlDB = new OdbcCommand(queryString, blogConnection);
OdbcDataReader reader = MySqlDB.ExecuteReader();
while (reader.NextResult())
{
recentPost[0] = reader.GetString(0);
recentPost[1] = reader.GetString(1);
}
recentPost[2] = reader.HasRows.ToString();
blogConnection.Close();
return recentPost;
}
}
In the queryString above RecentPost is a view I created to simplify the queryString since the query was a bit long.
I already know the view works. I tested it by opening phpMyAdmin from within the GoDaddy Hosting Center and executed the query above and I got the correct result, so I don't think the query/view is wrong.
The code-behind for the landing page:
protected void Page_Load(object sender, EventArgs e)
{
DAL dataAccess = new DAL();
String[] recentPost = dataAccess.GetRecentPost();
Title.Text = recentPost[0];
Post.Text = recentPost[1];
Extra.Text = recentPost[2];
}
So when my page loads the Title and Post texts are empty and Extra.Text is False (which from the DAL is the value from reader.HasRows).
So my guess is that its connecting fine and running the query but maybe on the wrong database? I don't know.
I also tried to debug but then my code throws an error about trying to connect to database.
So my questions are: Do you see anything wrong with the connection string?
If not do you see anything else than would cause a connection to be esablished, a query to run, no exceptions thrown but no results returned?
Any one with experience trying to grab data from thier own wordpress blog?
Thanks for the help - this one has been driving me crazy.
I don't know why my original code wasn't working but I solved my issue. For anyone else having this issue here is how I changed my code (in the GetRecentPost method) and solved my problem:
DataSet ds = new DataSet();
//ODBC
blogConnection.Open();
OdbcDataAdapter MySqlDB = new OdbcDataAdapter(queryString, blogConnection);
MySqlDB.Fill(ds);
return ds.Tables[0];
So instead of an array of strings I used a DataSet. Instead of using the OdbcDataReader I used an OdbcDataAdapter and populated the DataSet with the .Fill() method from OdbcDataAdapter I then returned the first table from the DataSet to my Page_Load method.
Here is my new Page_Load():
DataTable table = dataAccess.GetRecentPost();
if (table.Rows.Count > 0)
{
Title.Text = table.Rows[0]["title"].ToString();
Post.Text = table.Rows[0]["content"].ToString();
}
else
Extra.Text = table.Rows.Count.ToString(); \\if nothing was returned ouput the 0 just to be sure
Hope this helps anyone else with this issue
And thanks for anyone who took the time to look
I'm having trouble with the implementation of SqlDependency in my project.
I'm using SqlDependency in a WCF Service. WCF Service then holds in memory cache all results from all tables in order to have a huge speed gain. Everything seems to be working fine, except when I'm doing a table row update. If I add or delete a row in my table, DataContext is refreshed and cache is invalidated without problems. But when it comes to a table row update, nothing happens, the cache is not invalidated and when I look in debug mode at the content of DataContext, no changes seems to be there.
Here's the code I'm using (note that I'm using the System.Runtime.Caching object) :
public static List<T> LinqCache<T>(this Table<T> query) where T : class
{
ObjectCache cache = MemoryCache.Default;
string tableName =
query.Context.Mapping.GetTable(typeof(T)).TableName;
List<T> result = cache[tableName] as List<T>;
if (result == null)
{
using (SqlConnection conn =
new SqlConnection(query.Context.Connection.ConnectionString))
{
conn.Open();
SqlCommand cmd = new SqlCommand(
query.Context.GetCommand(query).CommandText, conn);
cmd.Notification = null;
cmd.NotificationAutoEnlist = true;
SqlDependency dependency = new SqlDependency(cmd);
SqlChangeMonitor sqlMonitor =
new SqlChangeMonitor(dependency);
CacheItemPolicy policy = new CacheItemPolicy();
policy.ChangeMonitors.Add(sqlMonitor);
cmd.ExecuteNonQuery();
result = query.ToList();
cache.Set(tableName, result, policy);
}
}
return result;
}
I created an extension method so all I have to do is to query any table like that :
List<MyTable> list = context.MyTable.LinqCache();
My DataContext is opened at the Global.asax Application_OnStart and stored in cache, so I can use it whenever I want in my WCF Service. As well at this moment I'm opening the SqlDependency object with
SqlDependency.Start(
ConfigurationManager.ConnectionStrings[myConnectionString].ConnectionString);
So, is that a limitation of SqlDependency, or I'm doing something wrong/missing something in the process?
I think the problem is that although you do all the work in setting up the command object you then do:
cmd.ExecuteNonQuery();
result = query.ToList();
Which is going to use your SQL Command and throw away the results then LINQ to SQL will generate it's own internally via query.ToList(). Thankfully you can ask LINQ to SQL to execute your own command and translate the results for you so try replacing those two lines with:
results = db.Translate<T>(cmd.ExecuteReader());