I want to get the value of a MySQL variable (example: max_allowed_packet) via jdbcTemplate. is this possible? if so, how ?
In SQL, I can do SHOW VARIABLES LIKE 'max_allowed_packet'; but how to do this via JDBCTemplate ?
Here is a solution
public List<Variable> findAllVariables() {
List<Variable> result = jdbcTemplate.query("SHOW GLOBAL VARIABLES", new VariableRowMapper());
//about 630 variables
return result;
}
Variable class:
public class Variable {
private String name;
private String value;
//getters and setters
}
VariableRowMapper class:
public class VariableRowMapper implements RowMapper<Variable> {
#Override
public Variable mapRow(ResultSet resultSet, int rowNum) throws SQLException {
String name = resultSet.getString("Variable_Name");
String value = resultSet.getString("Value");
return new Variable(name, value);
}
}
hope it helps.
I was particularly interested in getting the max_allowed_packet variable from the database. This below snippet does the trick.
private int fetchMaxAllowedPacketsFromDB(JdbcTemplate jdbcTemplate) {
final String sql = "SELECT ##GLOBAL.max_allowed_packet";
Integer maxAllowedPacketsFromDB = jdbcTemplate.queryForObject(sql, Integer.class);
log.info("##GLOBAL.max_allowed_packet : {}", maxAllowedPacketsFromDB);
return maxAllowedPacketsFromDB;
}
You can look at #Ali4j 's answer for a more generic/multi-variable requirement.
Or, You can refactor the snippet above to pass in a variable as argument, if you don't need the extra work of RowMappers
Related
I'm using MySQL DB.
My entity for the table is Account with the following fields:
id(long), balance (double), created_on(Date), currency(Enum).
When I'm doing a PUT request to update the account, I pass in the request body JSON.
I want to update, for example, only the balance, but the other columns' values to be saved.
In that case (I'm not passing the currency type) the balance is updated, but the currency has value NULL. Is that because it's enum?
I've tried using #DynamicUpdate annotation, but still, it doesn't have any change.
#RestController
public class AccountController {
#PutMapping("/accounts/{id}")
public void updateAccount(\#PathVariable long id, #RequestBody AccountDto accountDto) {
accountService.updateAccount(id, accountDto);
}
}
I'm using AccountDto (which I pass in the request body) and I'm calling the accountService
public void updateAccount(long id, AccountDto accountDto) {
Account account = accountRepository.getOne(id);
account.fromDto(accountDto);
this.accountRepository.save(account); }),
which calls the AccountRepository
public void fromDto(AccountDto accountDto) {
this.balance = accountDto.getBalance();
this.currency = accountDto.getCurrency();
}
Here is the AccountDto class:
public class AccountDto {
private long id;
#NotNull #PositiveOrZero
private double balance;
#NotNull #Enumerated(EnumType.STRING)
private Currency currency;
}
You need to perform a select query on Account entity and then update only the desired fields.
(Eg - making assumptions of my own of underlying method being used for accessing DB)
public updateAccount(AccountModel jsonBody) {
Account entity = accountRepository.findById(jsonBody.getAccountId());
entity.setBalance(jsonBody.getBalance());
accountRepository.save(entity);
}
If you get null as currency in the JSON you shouldn't update it:
So fromDto must look like:
public void fromDto(AccountDto accountDto) {
this.balance = accountDto.getBalance();
if (accountDto.getCurrency() != null) {
this.currency = accountDto.getCurrency();
}
}
I have some code that generates answers based on the user input. But in somecases i need to update the values later by calling SetAnswers But when i compile my code i get the following error:
NullReferenceException: Object reference not set to an instance of an object
I get this error on the line marked by the arrow.
See below for my code:
public class Generate_Questions : MonoBehaviour{
public Question q5, q4;
void Start(){
q4 = create_question("Select object to edit", EXTERNAL);
Visual_Question vq1 = new Visual_Question(1, q4, new vector(1,1,1), Ui, Canvas);
vq1.draw_question();
}
void Update(){
}
public class Visual_Question : Generate_Questions{
public Visual_Question(int order_id, Question q, Vector2 loc, Dictionary<string, RectTransform> ui, RectTransform canvas){
}
public void draw_question(){
q4.SetAnswers(new Answer[]{ <--------- this generates the error.
new Answer(null, "Select an option")
});
}
}
public class Question{
public string text;
public int answers_loc;
public List<Answer> answers;
public Question(string q_text, int answers_loc){
answers = new List<Answer>();
this.text = q_text;
this.answers_loc = answers_loc;
}
public void SetAnswers(Answer[] c_answers){
foreach(Answer answer in c_answers){
this.answers.Add(answer);
}
}
public bool CheckIfAnswersAvailable(){
if(answers.Count > 0){
return true;
}else{
return false;
}
}
public int QuestionLocation(){
return answers_loc;
}
}
public Question create_question(string text, int a_type){
Question Q = new Question(text, a_type);
return Q;
}
public interface IAnswer{
string GetText();
string GetDataType();
object GetValue();
Question GetNextQuestion();
}
public class Answer : IAnswer{
public string text;
public Question next = null;
public int? action = null;
public Element obj = null;
public string property = null;
public float? value = null;
public Answer(Question next, string text){
this.text = text;
this.next = next;
}
public Answer(Question next, string text, Element obj, int? action){
this.action = action;
this.text = text;
this.next = next;
this.obj = obj;
}
public Answer(Question next, string text, Element obj, int? action, string property, float? value){
this.action = action;
this.next = next;
this.text = text;
this.obj = obj;
this.property = property;
this.value = value;
}
public string GetText(){
return text;
}
public string GetDataType(){
throw new System.NotImplementedException();
}
public object GetValue(){
return value;
}
public Question GetNextQuestion(){
return next;
}
}
}
how would i go about fixing this problem? I am a complete newbie to c#. So my question may be already answered but i just dont know what i am looking for.
I assume that IAnswer[] is an interface and since you are trying to initialize an abstract object you get that runtime exception
NullReferenceException: Object reference not set to an instance of an object
if you want to create instance of IAnswer object you have to restructure it like class or structure.
Your class Visual_Question derives from Generate_Questions, so the member q4 that you use en draw_question is not initialized. This is not the member of Generated_Questions but a member of Visual_Question that is not initialized.
In Generate_Questions you are creating a new instance of Visual_Question and then immediately calling draw_question on that new instance. You now have 2 instances of a question (both derive from Generate_Questions), but only one of them has had the Start method, which initializes q4 called. If, however, you attempt to call Start from your second instance, you're going to find yourself in an infinite series of recursive calls and quickly crash with a different error (a stack overflow in this case).
One issue with the current code is that Generate_Questions sounds more like an action than a class. I'd suggest removing the inheritance from Visual_Question and make that an interface that you would implement on Question. Question should probably have the create_question method removed. That probably belongs in a MonoBehavior script (technically it's a factory method -- look up the factory pattern -- I'm not going to go into it here since this is a beginner topic).
Something like (obviously not complete):
public class Generate_Questions : MonoBehaviour
{
private IVisualQuestion q4;
void Start()
{
q4 = new Question("Select object to edit", EXTERNAL);
q4.DrawQuestion(new vector(1,1,1), Ui, Canvas)
}
void Update() {}
}
public interface IVisualQuestion
{
void DrawQuestion(Vector2 loc, Dictionary<string, RectTransform> ui, RectTransform canvas);
}
public class Question : IVisualQuestion
{
// ... insert the Question constructor and code here ...
// Implement VisualQuestion interface
public void DrawQuestion(Vector2 loc, Dictionary<string, RectTransform> ui, RectTransform canvas)
{
this.SetAnswers(new Answer[]{new Answer(null, "Select an option")});
}
}
In general, you probably don't need inheritance. As you learn more C#, you'll discover that when inheritance is going to help it will be clear. More often than not, using an interface is a far better and flexible approach. As a commenter noted, you probably don't want to inherit from MonoBehavior. You really only need that for classes that the Unity Engine is going to directly handle.
Another note: the convention in C# is to name methods, variables, etc. in PascalCase, not using underscores to separate words.
I need to insert a data multiple times in an web application. I am using selenium with testNG along with data driven framework.
I am using CSV file for reading the the input values.
Please find the sample code below.
public class TestData
{
private static String firstName;
public static String lastName;
#BeforeClass
public void beforeClass() throws IOException
{
reader = new CSVReader(new FileReader(fileName));
while((record = reader.readNext()) != null)
{
firstName = record[0];
lastName = record[1];
}
}
#Test
public void test1()
{
driver.findElement(By.id(id)).sendKeys(firstName);
driver.findElement(By.id(id)).click();
and so on....
}
#Test
public void test2()
{
driver.findElement(By.id(id)).sendKeys(lastName);
driver.findElement(By.id(id)).click();
and so on....
}
}
Here, I need to insert 3 records, but when I use the above code, only the 3rd record gets inserted.
Kindly help me to fix this issue.
Sample Input File
What you need here is a Factory powered by a DataProvider. The Factory would produce test class instances (A test class here is basically a regular class that contains one or more #Test methods housed in it). The data provider would basically feed the factory method with the data required to instantiate the test class.
Now your #Test methods would basically work with the data members in the instances to run its logic.
Here's a simple sample that shows this in action.
import org.assertj.core.api.Assertions;
import org.testng.annotations.DataProvider;
import org.testng.annotations.Factory;
import org.testng.annotations.Test;
public class TestClassSample {
private String firstName;
private String lastName;
#Factory(dataProvider = "dp")
public TestClassSample(String firstName, String lastName) {
this.firstName = firstName;
this.lastName = lastName;
}
#DataProvider(name = "dp")
public static Object[][] getData() {
//feel free to replace this with the logic that reads up a csv file (using CSVReader)
// and then translates it to a 2D array.
return new Object[][]{
{"Mohan", "Kumar"},
{"Kane", "Williams"},
{"Mark", "Henry"}
};
}
#Test
public void test1() {
Assertions.assertThat(this.firstName).isNotEmpty();
}
#Test
public void test2() {
Assertions.assertThat(this.lastName).isNotEmpty();
}
}
As per the data given by you , the while loop ends at the third record of CSV file. In each iteration your variables "firstName" and "lastName" are overwritten.
When the loop breaks , the variables store the lastly written values. So , use a better data structure for storing all values. I recommend map.
You can further club all the test cases in a single method , use invocationcount attribute in #Test annotation to repeat the execution for each entry from map. Add one more method with #BeforeTest for increment to next keyset in map.
I'm currently looking to store approximately 3.5 million photo's from approximately 100/200k users. I'm only using a mysql database on aws. My question is in regards to the most efficient way to store the photo reference. I'm only aware of two ways and I'm looking for an expert opinion.
Choice A
A user table with a photo_url column, in that column I would build a comma separated list of photo's that both maintain the name and sort order. The business logic would handle extracting the path from the photo name and append photo size. The downside is the processing expense.
Database example
"0ea102, e435b9, etc"
Business logic would build the following urls from photo name
/0e/a1/02.jpg
/0e/a1/02_thumb.jpg
/e4/35/b9.jpg
/e4/35/b9_thumb.jpg
Choice B - Relational Table joined on user table with the following fields. I'm just concerned I may have potential database performance issues.
pk
user_id
photo_url_800
photo_url_150
photo_url_45
order
Does anybody have any suggestions on the better solution?
The best and most common answer would be: choice B - Relational Table joined on user table with the following fields.
id
order
user_id
desc
photo_url_800
photo_url_150
photo_url_45
date_uploaded
Or a hybrid, wherein, you store the file names individually and add the photo directory with your business logic layer.
My analysis, your first option is a bad practice. Comma separated fields are not advisable for database. It would be difficult for you to update these fields and add description on it.
Regarding the table optimization, you might want to see these articles:
Optimizing MyISAM Queries
Optimizing InnoDB Queries
Here is an example of my final solution using the hibernate ORM, Christian Mark, and my hybrid solution.
#Entity
public class Photo extends StatefulEntity {
private static final String FILE_EXTENSION_JPEG = ".jpg";
private static final String ROOT_PHOTO_URL = "/photo/";
private static final String PHOTO_SIZE_800 = "_800";
private static final String PHOTO_SIZE_150 = "_150";
private static final String PHOTO_SIZE_100 = "_100";
private static final String PHOTO_SIZE_50 = "_50";
#ManyToOne
#JoinColumn(name = "profile_id", nullable = false)
private Profile profile;
//Example "a1d2b0" which will later get parsed into "/photo/a1/d2/b0_size.jpg"
//using the generatePhotoUrl business logic below.
#Column(nullable = false, length = 6)
private String fileName;
private boolean temp;
#Column(nullable = false)
private int orderBy;
#Temporal(TemporalType.TIMESTAMP)
private Date dateUploaded;
public Profile getProfile() {
return profile;
}
public void setProfile(Profile profile) {
this.profile = profile;
}
public String getFileName() {
return fileName;
}
public void setFileName(String fileName) {
this.fileName = fileName;
}
public Date getDateUploaded() {
return dateUploaded;
}
public void setDateUploaded(Date dateUploaded) {
this.dateUploaded = dateUploaded;
}
public boolean isTemp() {
return temp;
}
public void setTemp(boolean temp) {
this.temp = temp;
}
public int getOrderBy() {
return orderBy;
}
public void setOrderBy(int orderBy) {
this.orderBy = orderBy;
}
public String getPhotoSize800() {
return generatePhotoURL(PHOTO_SIZE_800);
}
public String getPhotoSize150() {
return generatePhotoURL(PHOTO_SIZE_150);
}
public String getPhotoSize100() {
return generatePhotoURL(PHOTO_SIZE_100);
}
public String getPhotoSize50() {
return generatePhotoURL(PHOTO_SIZE_50);
}
private String generatePhotoURL(String photoSize) {
String firstDir = getFileName().substring(0, 2);
String secondDir = getFileName().substring(2, 4);
String photoName = getFileName().substring(4, 6);
StringBuilder sb = new StringBuilder();
sb.append(ROOT_PHOTO_URL);
sb.append("/");
sb.append(firstDir);
sb.append("/");
sb.append(secondDir);
sb.append("/");
sb.append(photoName);
sb.append(photoSize);
sb.append(FILE_EXTENSION_JPEG);
return sb.toString();
}
}
public IEnumerable<T> ExecuteStoredProcedure<T>(params object[] parameters)
{
Type genericType = typeof(T);
string commandthing = genericType.Name.Replace("Result", "");
//_db is my Linq To Sql database
return _db.ExecuteQuery<T>(commandthing, parameters).AsEnumerable();
}
The stored procedure is named GetOrder and has a single int parameter of orderid. I'm calling the above like so:
SqlParameter parm1 = new SqlParameter("#orderid", SqlDbType.Int);
parm1.Value = 123;
var results =
_session.ExecuteStoredProcedure<GetOrderResult>(parm1).Single();
I'm receiving the following error: A query parameter cannot be of type 'System.Data.SqlClient.SqlParameter'
Thoughts? Or am I just missing something obvious?
Update: I'm trying to make this as generic as possible...my current thinking is that I'm going to have to do some string trickery to create the ExecuteQuery text and parameters.
Update: Posting below my Session Interface and my Linq to Sql Implementation of the interface...hopefully that will clarify what I'm attempting to do
public interface ISession : IDisposable
{
void CommitChanges();
void Delete<T>(Expression<Func<T, bool>> expression) where T : class;
void Delete<T>(T item) where T : class;
void DeleteAll<T>() where T : class;
T Single<T>(Expression<Func<T, bool>> expression) where T : class;
IQueryable<T> All<T>() where T : class;
void Add<T>(T item) where T : class;
void Add<T>(IEnumerable<T> items) where T : class;
void Update<T>(T item) where T : class;
IEnumerable<T> ExecuteStoredProcedure<T>(params object[] parameters);
}
public class LinqToSqlSession : ISession
{
public readonly Db _db;
public LinqToSqlSession()
{
_db = new Db(ConfigurationManager.ConnectionStrings[Environment.MachineName].ConnectionString);
}
public void CommitChanges()
{
_db.SubmitChanges();
}
/// <summary>
/// Gets the table provided by the type T and returns for querying
/// </summary>
private Table<T> GetTable<T>() where T : class
{
return _db.GetTable<T>();
}
public void Delete<T>(Expression<Func<T, bool>> expression) where T : class
{
var query = All<T>().Where(expression);
GetTable<T>().DeleteAllOnSubmit(query);
}
public void Delete<T>(T item) where T : class
{
GetTable<T>().DeleteOnSubmit(item);
}
public void DeleteAll<T>() where T : class
{
var query = All<T>();
GetTable<T>().DeleteAllOnSubmit(query);
}
public void Dispose()
{
_db.Dispose();
}
public T Single<T>(Expression<Func<T, bool>> expression) where T : class
{
return GetTable<T>().SingleOrDefault(expression);
}
public IEnumerable<T> ExecuteStoredProcedure<T>(params object[] parameters)
{
Type genericType = typeof(T);
string commandstring = genericType.Name.Replace("Result", "");
//_db is my Linq To Sql database
return _db.ExecuteQuery<T>(commandstring, parameters).AsEnumerable();
}
public IQueryable<T> All<T>() where T : class
{
return GetTable<T>().AsQueryable();
}
public void Add<T>(T item) where T : class
{
GetTable<T>().InsertOnSubmit(item);
}
public void Add<T>(IEnumerable<T> items) where T : class
{
GetTable<T>().InsertAllOnSubmit(items);
}
public void Update<T>(T item) where T : class
{
//nothing needed here
}
}
That isn't how you're supposed to wire up Stored Procedures with Linq-to-SQL. You should extend the DataContext and use ExecuteMethodCall instead:
Taken from MSDN:
public partial class MyDataContext
{
[Function()]
public IEnumerable<Customer> CustomerById(
[Parameter(Name = "CustomerID", DbType = "NChar(5)")]
string customerID)
{
IExecuteResult result = this.ExecuteMethodCall(this,
((MethodInfo)(MethodInfo.GetCurrentMethod())),
customerID);
return (IEnumerable<Customer>)(result.ReturnValue);
}
}
If you really must execute a sproc as a query (highly not recommended), then you have to preface the command with EXEC, and don't use SqlParameter either, the call would look like:
var results = context.ExecuteQuery<MyResult>("EXEC usp_MyProc {0}, {1}",
custID, custName);
(And I'll note, pre-emptively, that this is not a SQL injection vector because Linq to SQL turns the curly braces into a parameterized query.)
Read about how to call sprocs in linq to sql
http://weblogs.asp.net/scottgu/archive/2007/08/16/linq-to-sql-part-6-retrieving-data-using-stored-procedures.aspx
Had the same Problem. The following approach worked 4 me.
public interface IBusinessEntityRepository
{
.......
object CallStoredProcedure(string storedProcedureName, object[] parameters);
}
implementation in my linqtosql GenericLinqRepository
public object CallStoredProcedure(string storedProcedureName, object[] parameters)
{
DataContext dataContext = GetCurrentDataContext();
MethodInfo method = dataContext.GetType().GetMethod(storedProcedureName);
return method.Invoke(dataContext, parameters);
}
I'm sure there is a better way to do this...but this is presently working:
public IEnumerable<T> ExecuteStoredProcedure<T>(params object[] parameters)
{
Type genericType = typeof(T);
StringBuilder sb=new StringBuilder();
sb.Append("EXEC ");
sb.Append(genericType.Name.Replace("Result", " " ));
for (int i = 0; i < parameters.Count(); i++)
{
sb.Append("{" + i.ToString() + "} ");
}
string commandstring = sb.ToString();
return _db.ExecuteQuery<T>(commandstring, parameters);
}
It's a little bit brittle in that your parameters must be set up in the proper order, and it's probably offensive to some...but it does accomplish the goal.
You can use this instead:
new SqlParameter { ParameterName = "UserID", Value =txtuserid.Text }
This equivalent in System.Data.SqlClient to :
SqlParameter[] param=new SqlParameter[2];
param[0]=new SqlParameter("#UserID",txtuserid)