I use spring-data-cassandra-1.2.1.RELEASE to operate Cassandra database. Things all go well .But recent days I got a problem, when I using the code to get data:
public UserInfoCassandra selectUserInfo(String passport) {
Select select = QueryBuilder.select().from("userinfo");
select.setConsistencyLevel(ConsistencyLevel.QUORUM);
select.where(QueryBuilder.eq("passport", passport));
UserInfoCassandra userinfo = operations.selectOne(select,
UserInfoCassandra.class);
return userinfo;
}
there were many properties in userinfo , but I just get two the passport and uid properties.
I debug into the method,got that the data getting from db is right,all properties were ready.but when converting them to a java object ,some disappear.. the converting code:
protected <T> T selectOne(Select query, CassandraConverterRowCallback<T> readRowCallback) {
ResultSet resultSet = query(query);
Iterator<Row> iterator = resultSet.iterator();
if (iterator.hasNext()) {
Row row = iterator.next();
T result = readRowCallback.doWith(row);
if (iterator.hasNext()) {
throw new DuplicateKeyException("found two or more results in query " + query);
}
return result;
}
return null;
}
the row data is right ,but the result is wrong, who can help ?
Most probably your entity class and it's corresponding relational model are mismatched.
Related
I discovered a new interesting service and I'm trying to understand how it works. Please explain how to connect to my jOOQ database from another program?
MockDataProvider provider = new MyProvider();
MockConnection connection = new MockConnection(provider);
DSLContext create = DSL.using(connection, SQLDialect.H2);
Field<Integer> id = field(name("BOOK", "ID"), SQLDataType.INTEGER);
Field<String> book = field(name("BOOK", "NAME"), SQLDataType.VARCHAR);
So, I create but can I connect to it?
Here I have added your code, Lukas.
try (Statement s = connection.createStatement();
ResultSet rs = s.executeQuery("SELECT ...")
) {
while (rs.next())
System.out.println(rs.getString(1));
}
This example was found here
https://www.jooq.org/doc/3.7/manual/tools/jdbc-mocking/
public class MyProvider implements MockDataProvider {
#Override
public MockResult[] execute(MockExecuteContext ctx) throws SQLException {
// You might need a DSLContext to create org.jooq.Result and org.jooq.Record objects
//DSLContext create = DSL.using(SQLDialect.ORACLE);
DSLContext create = DSL.using(SQLDialect.H2);
MockResult[] mock = new MockResult[1];
// The execute context contains SQL string(s), bind values, and other meta-data
String sql = ctx.sql();
// Dynamic field creation
Field<Integer> id = field(name("AUTHOR", "ID"), SQLDataType.INTEGER);
Field<String> lastName = field(name("AUTHOR", "LAST_NAME"), SQLDataType.VARCHAR);
// Exceptions are propagated through the JDBC and jOOQ APIs
if (sql.toUpperCase().startsWith("DROP")) {
throw new SQLException("Statement not supported: " + sql);
}
// You decide, whether any given statement returns results, and how many
else if (sql.toUpperCase().startsWith("SELECT")) {
// Always return one record
Result<Record2<Integer, String>> result = create.newResult(id, lastName);
result.add(create
.newRecord(id, lastName)
.values(1, "Orwell"));
mock[0] = new MockResult(1, result);
}
// You can detect batch statements easily
else if (ctx.batch()) {
// [...]
}
return mock;
}
}
I'm not sure what lines 3-5 of your example are supposed to do, but if you implement your MockDataProvider and put that into a MockConnection, you just use that like any other JDBC connection, e.g.
try (Statement s = connection.createStatement();
ResultSet rs = s.executeQuery("SELECT ...")
) {
while (rs.next())
System.out.println(rs.getString(1));
}
Basically I am trying to get pagination working when requesting entities of azure table storage. i.e. Press next button gets the next 10 entities & Press previous button gets the previous 10 entities. A relatively close example Gaurav Mantri's Answer. But my question is how do I get the nextPartitionKey and nextRowKey from a HTML button attribute and store in to a array/list in order to keep track of current page so I can get the next/previous items?Code example would be very appreciated.
Thanks!
This is something I have right now which gets a range of data based on pageNumber request
private async Task<List<UserInfo>> queryPage(CloudTable peopleTable, string item, int pageNumber)
{
// Construct the query operation for all customer entities
TableQuery<CustomerEntity> query = new TableQuery<CustomerEntity>().Where(TableQuery.GenerateFilterCondition("PartitionKey", QueryComparisons.Equal, item));
// Print the fields for each customer.
TableContinuationToken token = null;
//TodoItem data = new TodoItem();
List<UserInfo> data = new List<UserInfo>();
do
{
TableQuerySegment<CustomerEntity> resultSegment = await peopleTable.ExecuteQuerySegmentedAsync(query, token);
token = resultSegment.ContinuationToken;
foreach (CustomerEntity entity in resultSegment.Results)
{
data.Add(new UserInfo
{
// add data
});
}
} while (token != null);
//get a subset of all entity
List<UserInfo> sublist = data.GetRange(0, pageNumber);
return sublist;
}
Managed to solved the problem under Gaurav's help.
Here is the code, not perfect but works.
private async Task<List<UserInfo>> queryPage(CloudTable peopleTable, string item, string NextPartitionKey , string NextRowKey, int itemNumber)
{
// Construct the query operation for all customer entities
TableQuery<CustomerEntity> query = new TableQuery<CustomerEntity>().Where(TableQuery.GenerateFilterCondition("PartitionKey", QueryComparisons.Equal, item)).Take(itemNumber);
// Print the fields for each customer.
List<UserInfo> data = new List<UserInfo>();
Tabletoken.NextPartitionKey = NextPartitionKey;
Tabletoken.NextRowKey = NextRowKey;
TableQuerySegment<CustomerEntity> resultSegment = await peopleTable.ExecuteQuerySegmentedAsync(query, Tabletoken);
Tabletoken = resultSegment.ContinuationToken;
foreach (CustomerEntity entity in resultSegment.Results)
{
data.Add(new UserInfo
{
//add data
});
}
return data;
}
private TableContinuationToken Tabletoken = new TableContinuationToken();
and declare it use a tuple.
Tuple<List<UserInfo>, string, string > tuple =
new Tuple<List<UserInfo>, string, string>(data, Tabletoken.NextPartitionKey, Tabletoken.NextRowKey);
I am developing an application, where I am trying to create a table if not exists and making a Query on it. It is working fine in normal cases. But for the first time , when the table is created , then when trying to Query the same table, the application is throwing :
IllegalArgumentException: Table xyz does not exist in keyspace my_ks
Same happens if I drop the table, and when my code recreates the table again.
For other cases, when the table exists, it is working fine. Is it some kind of replication issue, or should use a timeout from some time when the table is created for first time.
Following is the code snippet:
// Oredr 1: First this will be called
public boolean isSchemaExists() {
boolean isSchemaExists = false;
Statement statement = QueryBuilder
.select()
.countAll()
.from(keyspace_name, table_name);
statement.setConsistencyLevel(ConsistencyLevel.LOCAL_QUORUM);
try {
Session session = cassandraClient.getSession(someSessionKey);
ResultSet resultSet = null;
resultSet = session.execute(statement);
if (resultSet.one() != null) {
isSchemaExists = true;
}
} catch (all exception handling)
}
return isSchemaExists;
}
// Oredr 2: if previous method returns false then this will be get called
public void createSchema(String createTableScript) {
Session session = cassandraClient.getSession(someSessionKey);
if (isKeySpaceExists(keyspaceName, session)) {
session.execute("USE " + keyspaceName);
}
session.execute(createTableScript);
}
//Oredr 3: Now read the table, this is throwing the exception when the table
// is created for first time
public int readTable(){
Session session = cassandraClient.getSession(someSessionKey);
MappingManager manager = new MappingManager(session);
Mapper<MyPojo> mapper = manager.mapper(MyPojo.class);
Statement statement = QueryBuilder
.select()
.from(keyspaceName, tableName)
.where(eq("col_1", someValue)).and(eq("col_2", someValue));
statement.setConsistencyLevel(ConsistencyLevel.LOCAL_QUORUM);
ResultSet resultSet = session.execute(statement);
result = mapper.map(resultSet);
for (MyPojo myPojo : result) {
return myPojo.getCol1();
}
}
In isSchemaExists function use system.tables.
SELECT * FROM system.tables WHERE keyspace_name='YOUR KEYSPACE' AND table_name='YOUR TABLE'
Corresponding Java Code:
Statement statement = QueryBuilder
.select()
.from("system", "tables")
.where(eq("keyspace_name", keyspace)).and(eq("table_name", table));
It seems like in isSchemaExists you are using actual table and keyspace which will not exist when dropped or not created. That's the reason it is throwing you error table does not exist.
Why is data read from SqlDataReader not available to a method call?
I have a table, with 'id' as column in it.
When I make a query to database, it returns rows.
This code doesnt work (Says 'id' column doesnt exist):
con.Open();
SqlDataReader requestReader = cmd.ExecuteReader();
if (requestReader.HasRows)
{
DataTable requestTable = requestReader.GetSchemaTable();
request = ReadRequest(requestTable.Rows[0]);
}
con.Close();
while this one works:
con.Open();
SqlDataReader requestReader = cmd.ExecuteReader();
if (requestReader.HasRows)
{
DataTable requestTable = requestReader.GetSchemaTable();
var requestRow = requestTable.Rows[0];
request = new Request();
request.UniqueId = (string)requestRow["id"];
}
con.Close();
You are using DataReader.GetSchemaTable which returns a DataTable with all schema informations for a given table.
It has following columns:
ColumnName
ColumnOrdinal
ColumnSize
NumericPrecision
// .. 26 others
So you don't find your id-column which belongs to your table. That's why you get the error "'id' column doesnt exist". I doubt that your second approach works. I don't see why you need GetSchemaTable at all. You just have to advance the reader to the next record:
if (requestReader.HasRows && requestReader.Read())
{
int id = requestReader.GetInt32(requestReader.GetOrdinal("id"));
// ...
}
I am building an asp.net site in .net framework 4.0, and I am stuck at the method that supposed to call a .cs class and get the query result back here is my method call and method
1: method call form aspx.cs page:
helper cls = new helper();
var query = cls.GetQuery(GroupID,emailCap);
2: Method in helper class:
public IQueryable<VariablesForIQueryble> GetQuery(int incomingGroupID, int incomingEmailCap)
{
var ctx = new some connection_Connection();
ObjectSet<Members1> members = ctx.Members11;
ObjectSet<groupMember> groupMembers = ctx.groupMembers;
var query = from m in members
join gm in groupMembers on m.MemberID equals gm.MemID
where (gm.groupID == incomingGroupID) && (m.EmailCap == incomingEmailCap)
select new VariablesForIQueryble(m.MemberID, m.MemberFirst, m.MemberLast, m.MemberEmail, m.ValidEmail, m.EmailCap);
//select new {m.MemberID, m.MemberFirst, m.MemberLast, m.MemberEmail, m.ValidEmail, m.EmailCap};
return query ;
}
I tried the above code with IEnumerable too without any luck. This is the code for class VariablesForIQueryble:
3:Class it self for taking anonymouse type and cast it to proper types:
public class VariablesForIQueryble
{
private int _emailCap;
public int EmailCap
{
get { return _emailCap; }
set { _emailCap = value; }
}`....................................
4: and a constructor:
public VariablesForIQueryble(int memberID, string memberFirst, string memberLast, string memberEmail, int? validEmail, int? emailCap)
{
this.EmailCap = (int) emailCap;
.........................
}
I can't seem to get the query result back, first it told me anonymous type problem, I made a class after reading this: link text; and now it tells me constructors with parameters not supported. Now I am an intermediate developer, is there an easy solution to this or do I have to take my query back to the .aspx.cs page.
If you want to project to a specific type .NET type like this you will need to force the query to actually happen using either .AsEnumerable() or .ToList() and then use .Select() against linq to objects.
You could leave your original anonymous type in to specify what you want back from the database, then call .ToList() on it and then .Select(...) to reproject.
You can also clean up your code somewhat by using an Entity Association between Groups and Members using a FK association in the database. Then the query becomes a much simpler:
var result = ctx.Members11.Include("Group").Where(m => m.Group.groupID == incomingGroupID && m.EmailCap == incomingEmailCap);
You still have the issue of having to do a select to specify which columns to return and then calling .ToList() to force execution before reprojecting to your new type.
Another alternative is to create a view in your database and import that as an Entity into the Entity Designer.
Used reflection to solve the problem:
A: Query, not using custom made "VariablesForIQueryble" class any more:
//Method in helper class
public IEnumerable GetQuery(int incomingGroupID, int incomingEmailCap)
{
var ctx = new some_Connection();
ObjectSet<Members1> members = ctx.Members11;
ObjectSet<groupMember> groupMembers = ctx.groupMembers;
var query = from m in members
join gm in groupMembers on m.MemberID equals gm.MemID
where ((gm.groupID == incomingGroupID) && (m.EmailCap == incomingEmailCap)) //select m;
select new { m.MemberID, m.MemberFirst, m.MemberLast, m.MemberEmail, m.ValidEmail, m.EmailCap };
//select new VariablesForIQueryble (m.MemberID, m.MemberFirst, m.MemberLast, m.MemberEmail, m.ValidEmail, m.EmailCap);
//List<object> lst = new List<object>();
//foreach (var i in query)
//{
// lst.Add(i.MemberEmail);
//}
//return lst;
//return query.Select(x => new{x.MemberEmail,x.MemberID,x.ValidEmail,x.MemberFirst,x.MemberLast}).ToList();
return query;
}
B:Code to catch objects and conversion of those objects using reflection
helper cls = new helper();
var query = cls.GetQuery(GroupID,emailCap);
if (query != null)
{
foreach (var objRow in query)
{
System.Type type = objRow.GetType();
int memberId = (int)type.GetProperty("MemberID").GetValue(objRow, null);
string memberEmail = (string)type.GetProperty("MemberEmail").GetValue(objRow, null);
}
else
{
something else....
}