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How to find the selected id in my List<String> ids arraylist?

Here is my code. I am trying to use JUnit to test the deleteUsers() method, but everytime I write my test, it deletes all the users that I have in the database. How can i delete a single user? Below is the code for the method and for the test.
#Override
public boolean deleteUsers(List<String> ids) throws Exception {
StringBuilder sql = new StringBuilder();
sql.append("delete from user where ");
for (String id : ids) {
sql.append(" id = ? or");
}
String strSql = sql.toString().substring(0, sql.length() - 2) + ";";
PreparedStatement preparedStatement = this.connection.prepareStatement(strSql);
for (int i = 0; i < ids.size(); i++) {
preparedStatement.setInt(1 + i, Integer.parseInt(ids.get(i)));
}
int lines = preparedStatement.executeUpdate();
preparedStatement.close();
return lines > 0;
}

You're missing a check for empty input. In your test you pass an empty list to deleteUsers which results in this SQL statement:
delete from user wher;
I'd expect that the DBMS would reject this as invalid SQL but perhaps there are some where this is interpreted as delete from user which simply deletes all users. (As #SteveBosman pointed out the wher is interpreted as table alias as it is - due to the missing last e - no reserved word anymoere)
Basically you have 2 options. Either deleting all users by passing an empty list is a valid use case - in which case you should handle it properly by producing proper SQL. Or this is not expected and you should adapt your code to throw an Exception if ids is empty.
#Override
public boolean deleteUsers(List<String> ids) throws Exception {
if (ids == null || ids.size() == 0) {
throw new IllegalArgumentException("List of IDs must not be empty");
}
...
}
You could of course return false in case of an empty input as well to indicate no users were deleted.
To pass values to the deleteUsers method in your test you need to add values to the used list:
userDAOImpl.addUser("admin3", "111222");
final List<String> idsToDelete = new ArrayList<>();
idsToDelete.add("111222");
userDAOImpl.deleteUsers(idsToDelete);

The problem is caused by how the SQL is built. When deleteUsers is passed an empty list then the generated SQL will be:
delete from user wher
which will result in all data being deleted (the table user is given the alias "wher"). I highly recommend checking at the start of the method if the collection is empty and either raising an exception or returning.
Add the following check
if (ids == null || ids.isEmpty()) {
throw new IllegalArgumentException("ids must not be empty");
}

StringBuilder sql = new StringBuilder();
sql.append("delete from user where");
String orClause = "";
for (String id : ids) {
sql.append(orClause);
sql.append(" id = ?");
orClause = " or";
}

Spring Hibernate generate dynamic query

I am using hibernate spring where I need to generate query on a condition.
DAO.java
public ReturnData updateUserDetails(Users users, String mailID)
{
if(!users.getImageURL().equals(""))
{
Query query = this.sessionFactory.getCurrentSession().createQuery("UPDATE users SET emailID=:email_ID, name=:name, imageURL=:imageURL WHERE emailID=:emailID")
//setString....
}
else
{
Query query = this.sessionFactory.getCurrentSession().createQuery("UPDATE users SET emailID=:email_ID, name=:name WHERE emailID=:emailID")
//setString....
}
}
In the above code, I check if image also has been uploaded or not. On the basis of this condition, I have to dynamically generate query. I have to rewrite the whole code for query+execution 2 times. Is it the good way, or is there any better way to do this?

You can dynamically append the query conditions to the query string if they are not null. After getting the final list of conditions, you can create Hibernate query.
StringBuilder sqlQuery = new StringBuilder();
Map<String,Object> parameters = new HashMap<String,Object>();
boolean isFirstSearchCriterion = true;
sqlQuery.append("UPDATE users");
if(email_ID!= null && !email_ID.trim().equals("")) {
if(isFirstSearchCriterion) {
sqlQuery.append(" set emailID= :email_ID");
} else {
sqlQuery.append(" and emailID= :email_ID");
}
parameters.put("email_ID",email_ID);
isFirstSearchCriterion = false;
}
if(name!= null && !name.trim().equals("")) {
if(isFirstSearchCriterion) {
sqlQuery.append(" set name= :name");
} else {
sqlQuery.append(" and name= :name");
}
parameters.put("name",name);
isFirstSearchCriterion = false;
}
if(imageURL!= null && !imageURL.trim().equals("")) {
if(isFirstSearchCriterion) {
sqlQuery.append(" set imageURL= :imageURL");
} else {
sqlQuery.append(" and imageURL= :imageURL");
}
parameters.put("imageURL",imageURL);
isFirstSearchCriterion = false;
}
Query query = this.sessionFactory.getCurrentSession().createQuery(sqlQuery);
Set<String> parameterSet = parameters.keySet();
for (Iterator<String> it = parameterSet.iterator(); it.hasNext();) {
String parameter = it.next();
query.setParameter(parameter, parameters.get(parameter));
}

You can simply do without checking empty String, if user has image url it will add in column or else empty url will be pass on.
public ReturnData updateUserDetails(Users users, String mailID)
{
Query query = this.sessionFactory.getCurrentSession().createQuery("UPDATE users SET emailID=:email_ID, name=:name, imageURL=:imageURL WHERE emailID=:emailID")
query.setParameter("imageURL",users.getImageURL(), Hibernate.STRING);
}

What's the best way to handle recurring tasks like CRUD operations in Java?

I'm trying to write classes and methods to minimize recurring tasks.
For instance, I'm planning to write a generic DAO (Database Access Object) class in Java which can do the basic crud operations by accpeting the inputdata.
For example, the following is a method I just started writing which accepts a Bean as a parameter and constructs an insert query.
public boolean insert(Object object) throws NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, SQLException, InvalidDataException {
String tableName = object.getClass().getSimpleName().toLowerCase() + "s";
Field[] fields = object.getClass().getDeclaredFields();
ArrayList<String> columnNames = new ArrayList<>();
for (Field field : fields) {
String fieldName = field.getName();
Method method = object.getClass().getMethod("get" + field.getName().substring(0, 1).toUpperCase() + field.getName().substring(1));
if ("id".equalsIgnoreCase(fieldName)) {
continue;
}
if (method.invoke(object) != null || "created".equalsIgnoreCase(fieldName) || "modified".equalsIgnoreCase(fieldName)) {
columnNames.add(General.toUnderscore(fieldName));
}
}
String sqlQuery = generateInsertSQLQuery(tableName, columnNames);
System.out.println(sqlQuery);
PreparedStatement ps = this.conn.prepareStatement(sqlQuery);
int index = 1;
for (Field field : fields) {
String fieldName = field.getName();
Method method = object.getClass().getMethod("get" + field.getName().substring(0, 1).toUpperCase() + field.getName().substring(1));
if ("created".equalsIgnoreCase(fieldName) || "modified".equalsIgnoreCase(fieldName)) {
ps.setDate(index++, new java.sql.Date((new java.util.Date()).getTime()));
} else {
if (method.invoke(object) != null) {
if (field.getType() == String.class) {
ps.setString(index++, (String) method.invoke(object));
} else if (field.getType() == Integer.class) {
ps.setInt(index++, (Integer) method.invoke(object));
} else if (field.getType() == Long.class) {
ps.setLong(index++, (Long) method.invoke(object));
} else if (field.getType() == java.util.Date.class) {
java.sql.Date date = new java.sql.Date(((java.util.Date) method.invoke(object)).getTime());
ps.setDate(index++, date);
}
}
}
}
ps.executeUpdate();
return true;
}
The bean is a pretty standard class with getters and setters. My question is, is this a right approach to handle things in Java ?
Are there any popular resources which already accomplished this ?
Kindly guide me with your valuable inputs.

I would recommend the Spring Framework with the Spring Data JPA project.
http://projects.spring.io/spring-data-jpa/
You can annotate any JavaBean with the correct JPA annotations. Then create an interface which extends the Spring CrudRepository. Some configuration and add the Hibernate or EclipseLink dependencies. Ready!
http://docs.oracle.com/javaee/6/tutorial/doc/bnbpz.html
A good tutorial:
http://spring.io/guides/gs/accessing-data-jpa

Look at Spring Data: http://projects.spring.io/spring-data/
Generally instead of questions like this you should ask "How can I do it in Spring?" Spring is already one level above everything - particularly ORMs. It makes most of the tedious programming tasks declarative,

Hibernate and the Java Persistence API (hibernate based) does this reflection tricky for you.

Hibernate query restrictions using URL key/value style parameters

I'm using Tapestry5 and Hibernate. I'm trying to build a criteria query that uses dynamic restrictions generated from the URL. My URL context is designed like a key/value pair.
Example
www.mywebsite.com/make/ford/model/focus/year/2009
I decode the parameters as followed
private Map<String, String> queryParameters;
private List<Vehicle> vehicles;
void onActivate(EventContext context) {
//Count is 6 - make/ford/model/focus/year/2009
int count = context.getCount();
if (count > 0) {
int i;
for (i = 0; (i + 1) < count; i += 2) {
String name = context.get(String.class, i);
String value = context.get(String.class, i + 1);
example "make"
System.out.println("name " + name);
example "ford"
System.out.println("value " + value);
this.queryParameters.put(name, value);
}
}
this.vehicles = this.session.createCriteria(Vehicle.class)
...add dynamic restrictions.
}
I was hoping someone could help me to figure out how to dynamically add the list of restrictions to my query. I'm sure this has been done, so if anybody knows of a post, that would be helpful too. Thanks

Exactly as the other answer said, but here more spelt out. I think the crux of your question is really 'show me how to add a restriction'. That is my interpretation anyhow.
You need to decode each restriction into its own field.
You need to know the Java entity property name for each field.
Then build a Map of these 2 things, the key is the known static Java entity property name and the value is the URL decoded data (possibly with type conversion).
private Map<String, Object> queryParameters;
private List<Vehicle> vehicles;
void onActivate(EventContext context) {
//Count is 6 - make/ford/model/focus/year/2009
int count = context.getCount();
queryParameters = new HashMap<String,Object>();
if (count > 0) {
int i;
for (i = 0; (i + 1) < count; i += 2) {
String name = context.get(String.class, i);
String value = context.get(String.class, i + 1);
Object sqlValue = value;
if("foobar".equals(name)) {
// sometime you don't want a String type for SQL compasition
// so convert it
sqlValue = UtilityClass.doTypeConversionForFoobar(value);
} else if("search".equals(name) ||
"model".equals(name) ||
"year".equals(name)) {
// no-op this is valid 'name'
} else if("make".equals(name)) {
// this is a suggestion depends on your project conf
name = "vehicleMake.name";
} else {
continue; // ignore values we did not expect
}
// FIXME: You should validate all 'name' values
// to be valid and/or convert to Java property names here
System.out.println("name " + name);
System.out.println("value " + value);
this.queryParameters.put(name, sqlValue);
}
}
Criteria crit = this.session.createCriteria(Vehicle.class)
for(Map.Entry<String,Object> e : this.queryParameters.entrySet()) {
String n = e.getKey();
Object v = e.getValue();
// Sometimes you don't want a direct compare 'Restructions.eq()'
if("search".equals(n))
crit.add(Restrictions.like(n, "%" + v + "%"));
else // Most of the time you do
crit.add(Restrictions.eq(n, v));
}
this.vehicles = crit.list(); // run query
}
See also https://docs.jboss.org/hibernate/orm/3.5/reference/en/html/querycriteria.html
With the above there should be no risk of SQL injection, since the "name" and "n" part should be 100% validated against a known good list. The "value" and "v" is correctly escaped, just like using SQL position placeholder '?'.
E&OE

I would assume you would just loop over the parameters Map and add a Restriction for each pair.
Be aware that this will open you up to sql injection attacks if you are not careful. the easiest way to protect against this would be to check the keys against the known Vehicle properties before adding to the Criteria.

Another option would be to create an example query by building an object from the name/value pairs:
Vehicle vehicle = new Vehicle();
int count = context.getCount();
int i;
for (i = 0; (i + 1) < count; i += 2) {
String name = context.get(String.class, i);
String value = context.get(String.class, i + 1);
// This will call the setter for the name, passing the value
// So if name is 'make' and value is 'ford', it will call vehicle.setMake('ford')
BeantUtils.setProperty(vehicle, name, value);
}
// This is using a Hibernate example query:
vehicles = session.createCriteria(Vehicle.class).add(Example.create(vehicle)).list();
See BeanUtils.setProperty and Example Queries for more info.
That assumes you are allowing only one value per property and that the query parameters map to the property names correctly. There may also be conversion issues to think about but I think setProperty handles the common ones.

If they are query paramaters you should treat them as query parameters instead of path parameters. Your URL should look something like:
www.mywebsite.com/vehicles?make=ford&model=focus&year=2009
and your code should look something like this:
public class Vehicles {
#ActivationRequestParameter
private String make;
#ActivationRequestParameter
private String model;
#ActivationRequestParameter
private String year;
#Inject
private Session session;
#OnEvent(EventConstants.ACTIVATE)
void activate() {
Criteria criteria = session.createCriteria(Vehicle.class);
if (make != null) criteria.add(Restrictions.eq("make", make));
if (model != null) criteria.add(Restrictions.eq("model", model));
if (year != null) criteria.add(Restrictions.eq("year", year));
vehicles = criteria.list();
}
}
Assuming you are using the Grid component to display the vehicles I'd highly recommend using the HibernateGridDataSource instead of making the query in the "activate" event handler.
public class Vehicles {
#ActivationRequestParameter
private String make;
#ActivationRequestParameter
private String model;
#ActivationRequestParameter
private String year;
#Inject
private Session session;
#OnEvent(EventConstants.ACTIVATE)
void activate() {
}
public GridDataSource getVehicles() {
return new HibernateGridDataSource(session, Vehicles.class) {
#Override
protected void applyAdditionalConstraints(Criteria criteria) {
if (make != null) criteria.add(Restrictions.eq("make", make));
if (model != null) criteria.add(Restrictions.eq("model", model));
if (year != null) criteria.add(Restrictions.eq("year", year));
}
};
}
}

Why does the NetBeans Java debugger never reach this code?

I'm trying to debug a method in Java using NetBeans.
That method is:
public Integer getNumberOfClamps(Locations paLocation) {
Integer ret = -1;
List list = new ArrayList();
String removeme = "ABC";
if (paLocation == null) {
return ret;
}
try {
IO io = new IO(this.getSchemaName());
Session session = io.getSession();
String sql = "select count(*) from assets a join assettypes at on (at.id = a.assettype_id) ";
sql += "where a.currentlocation_id = " + paLocation.getId() + " and at.clamp = 1 and at.active = 1;";
list = session.createQuery(sql).list();
// for some reason, list is empty yet MySQL reports 40 records
// and the following two lines are never reached!
ret = list.size();
removeme = "WHAT???";
} catch (Exception ex) {
ret = -1; // explicitly set return
} finally {
return ret;
}
}
Towards the middle of the method you will see list = session.createQuery(sql).list();
For some reason, this is returning an empty list even though when the SQL is run manually, I get 40 results.
But the odd part is that once the .list() is called, it jumps to the finally block and never reaches the rest! So for testing, 'removeme' should equal WHAT??? but the debugger reports it as still ABC.
What gives?

You are using the wrong method. 'createQuery' is expecting HQL syntax. Change your method to 'createSQLQuery'