I am trying to implement calling read() method in the itemReader multiple times.
For Eg:
I have a list of POJO in which I will have one string variable with values either A or B or C.
I have to sort this list based on alphabetical order and segment it into three list for each value. i.e., list for value A and list for value B
and list for value C.
I need to send each list to the read() method in the itemReader one by one.
Once List for A is processed and write, then I need to send List for B and so on..
Is this doable? Any help is appreciated.
Although I am not very clear on what you are trying to achieve, I don't see any reason it cannot be done.
I assume you mean either of this:
1. You want the "item" to be process to be a whole list of POJO with same ABC Type, or
2. You want the item to be the POJO itself, and you want them to be processed in order of ABC Type
2 is straight-forward. At the first read, prepare all the POJOs, sort it. I assume they are in some kind of
In psuedo code, it looks like this
class MyReader implements ItemReader<MyPojo> {
private List<MyPojo> values;
MyPojo read() {
if (values == null) {
values = getPojos();
sort values;
}
if (values.isEmpty()){
return null;
} else {
return values.popFront();
}
}
}
1 is nothing more complicated. You will need to group POJOs with same ABC type in same list, and return the lists one by one. It can be easily done by using a TreeMap<String, List<MyPojo>>
In psuedo code, it looks like this
class MyReader implements ItemReader<List<MyPojo>> { // note the item is List<MyPojo>
private NavigableMap<String, List<MyPojo>> values;
List<MyPojo> read() {
if (values == null) {
values = new TreeMap<>();
pojos = getPojos();
for (pojo : pojos) {
if (values do not contain pojo.abcType() ) {
values.put(pojo.abcType(), new ArrayList(pojo));
} else {
values.get(pojo.abcType()).add(pojo);
}
}
}
if (values.isEmpty()){
return null;
} else {
return values.popFirstEntry().value();
}
}
}
If your list of items is fully available (you have a List<Pojo> loaded with all items) you can:
use a ListItemReader and inject into the ordered list
use a custom ItemReader and sort items after first ItemReader.read()
About break the best way is to use a custom CompletionPolicy based on pojo 'string variable'; in this manner your writer will receive a list where POJO's 'string variable' has the same values for all list items (check How to read csv lines chunked by id-column with Spring-Batch? for sample code).
Related
With arrays you can use a subscript to access Array Elements directly. You can read or write to them. With Sets I am not sure of a way to write its Elements.
For example, if I access a set element matching a condition I'm only able to read the element. It is passed by copy and I can't therefore write to the original.
For example:
columns.first(
where: {
$0.header.last == Character(String(i))
}
)?.cells.append(value: addValue)
// ERROR: Cannot use mutating member on immutable value: function call returns immutable value
You can't just change things inside a set, because of how a (hash) set works. Changing them would possibly change their hash value, making the set into an invalid state.
Therefore, you would have to take the thing you want to change out of the set, change it, then put it back.
if var thing = columns.first(
where: {
$0.header.last == Character(String(i))
}) {
columns.remove(thing)
thing.cells.append(value: addValue)
columns.insert(thing)
}
If the == operator on Column doesn't care about cells (i.e. adding cells to a column doesn't suddenly make two originally equal columns unequal and vice versa), then you could use update instead:
if var thing = columns.first(
where: {
$0.header.last == Character(String(i))
}) {
thing.cells.append(value: addValue)
columns.update(thing)
}
As you can see, it's quite a lot of work, so maybe sets aren't a suitable data structure to use in this situation. Have you considered using an array instead? :)
private var _columns: [Column]
public var columns : [Column] {
get { _columns }
set { _columns = Array(Set(newValue)) }
// or any other way to remove duplicate as described here: https://stackoverflow.com/questions/25738817/removing-duplicate-elements-from-an-array-in-swift
}
You are getting the error because columns might be a set of struct. So columns.first will give you an immutable value. If you were to use a class, you will get a mutable result from columns.first and your code will work as expected.
Otherwise, you will have to do as explained by #Sweeper in his answer.
Following is the code, I am trying:
public List<Movie> GetMovies()
{
Func<Movie, Movie> prepareMovieOutput =
(input) =>
{
input.DisplayHtmlContent = String.Empty;
return input;
};
var moviesOutput = from m in db.Movies.ToList()
select prepareMovieOutput(m);
return moviesOutput.ToList();
}
public List<Movie> SearchMovies(string searchTerm)
{
var moviesOutput = db.Movies.Where(m => m.Name.Contains(searchTerm)).ToList();
return moviesOutput.ToList();
}
The GetMovies function is working properly, as it returns List collection after clearing DisplayHtmlContent field, whereas, SearchMovies function is supposed to return Movie collection with DisplayHtmlContent field, but inspite of that it returns that field empty.
If I set DisplayHtmlContent to some fixed value (like, "ABC"),both GetMovies and SearchMovies return the list with all Movie having DisplayHtmlContent field as "ABC" value. I don't understand why the function defined in one method should affect the other one. and also how to fix this issue?
Ideally, I want GetMovies to hold all Movie with that particular field as empty string, and SearchMovies to hold all Movie with that field containing value.
Any help on this much appreciated.
this was due to the use of repository. I have removed it and it started working fine. with having EF 5, I didn't need to use repository
I'm trying to convert an entire column values into a arrayList using ormlite on android, is this possible, with direct api?
Using raw results i get close, but not quite:
GenericRawResults<String[]> rawResults =
getHelper().getMyProcessDao().queryRaw(
queryBuild.selectColumns("nid").prepareStatementString());
List<String[]> result = rawResults.getResults();
Hrm. I'm not sure this is what you want. However, one way to accomplish what you ask for specifically is through by using the RawRowMapper which can be passed to ORMLite's DAO method: dao.queryRaw(String, Rowmapper, String...).
Something like the following should work:
RawRowMapper<Integer> mapper = new RawRowMapper<Integer>() {
public Integer mapRow(String[] columnNames, String[] resultColumns) {
// maybe you should verify that there _is_ only 1 column here
// maybe you should handle the possibility of a bad number and throw
return Integer.parseInt(resultColumns[0]);
}
};
GenericRawResults<Integer> rawResults =
getHelper().getMyProcessDao().queryRaw(
queryBuild.selectColumns("nid").prepareStatementString(), mapper);
List<Integer> list = rawResults.getResults();
What is the best way of handling trying to get data from a DataReader that has more than one column with the same name?
Because of the amount of work involved and because we don't want to lose support from a vendor by changing the stored procedures we are using to retrieve the data, I am trying to find another way to get access to a column that shows up more than once in a datareader without having to rewrite the stored procedures.
Any Ideas?
EDIT:
Ok, the function that actually populates from a datareader is used in multiple places so there is a possibility that the function can be called by different stored procedures. What I did was to do a GetName using the index to check if it is the correct column, and if it is, then pull its value.
If you know the index of the column, then access it by the index.
Can't you use column ordinals? 0 for the 1st, 1 for the 2nd, and so on?
You will have to reference the column by index no; i.e. reader[5].ToString(); to read the data in column 5.
Based on original poster's approach described in the "Edit" paragraph, here's an extension method that will give the value based on the column name and the index of that name, e.g., 0 for the first instance of name, 1 for the second, etc:
using System;
namespace WhateverProject {
internal static class Extentions {
// If a query returns MULTIPLE columns with the SAME name, this allows us to get the Nth value of a given name.
public static object NamedValue(this System.Data.IDataRecord reader, string name, int index) {
if (string.IsNullOrWhiteSpace(name)) return null;
if (reader == null) return null;
var foundIndex = 0;
for (var i = 0; i < reader.FieldCount; i++) {
if (!reader.GetName(i).Equals(name, StringComparison.CurrentCultureIgnoreCase)) continue;
if (index == foundIndex) return reader[i];
foundIndex++;
}
return false;
}
}
}
Use it thus:
var value1 = reader.NamedValue("duplicatedColumnName", 0);
var value2 = reader.NamedValue("duplicatedColumnName", 1);
I'm writing a custom validator that will validate against multiple other form element values. In my form, I call my custom validator like this:
$textFieldOne = new Zend_Form_Element_Text('textFieldOne');
$textFieldOne->setAllowEmpty(false)
->addValidator('OnlyOneHasValue', false, array(array('textFieldTwo', 'textFieldThree')));
My validator will check that only one of those three fields (textFieldOne, textFieldTwo, textFieldThree) has a value. I want to prevent a future developer from accidentally passing the same field twice.
$textFieldOne->addValidator('OnlyOneHasValue', false, array(array('textFieldOne', 'textFieldTwo', 'textFieldThree')));
So far, my validator works perfectly, except when I pass the same field name as the field that has the valiator set on it.
In my validator, you can see that I am checking that the value (of the element with the validator set on it). I'm also checking the values of the other fields that were passed to the validator.
public function isValid($value, $context = null) {
$this->_setValue($value);
$this->_context = $context;
if ($this->valueIsNotEmpty()) {
if ($this->numberOfFieldsWithAValue() == 0) {
return true;
}
$this->_error(self::MULTIPLE_VALUES);
return false;
}
if ($this->numberOfFieldsWithAValue() == 0) {
$this->_error(self::ALL_EMPTY);
return false;
}
if ($this->numberOfFieldsWithAValue() == 1) {
return true;
}
if ($this->numberOfFieldsWithAValue() > 1) {
$this->_error(self::MULTIPLE_VALUES);
return false;
}
}
private function valueIsNotEmpty() {
return Zend_Validate::is($this->_value, 'NotEmpty');
}
private function numberOfFieldsWithAValue() {
$fieldsWithValue = 0;
foreach ($this->_fieldsToMatch as $fieldName) {
if (isset($this->_context[$fieldName]) && Zend_Validate::is($this->_context[$fieldName], 'NotEmpty')) {
$fieldsWithValue++;
}
}
return $fieldsWithValue;
}
My solution is to either...
A. Let the developer figure out there is a certain way to do it.
B. Ignore $value, forcing you to pass all the elements (which isn't much different than the first option).
or C. (if possible) Find the name of the element that called my validator in the first place and ignore it from the list of $fieldsWithValue.
I don't think there is a way to apply a validator on a form without attaching it to an element, but that would be even better, if it were an option.
How can I solve this problem?
Normaly i'd advise against such things, but, in this case I believe a static member in your class would actually provide a good solution to this problem.
With a static member, you can set it to the value in the first time the isValid is called, and check against it in subsequent calls, thus giving you a mechanism for this.
You may want to set this up to use some array in the configuration options, so that you can namespace and allow multiple instances of the validator to exist happily alongside each other for different sets.
The only problem that you really have to decide how to overcome, is where you wish to display the error, as yes the form itself does not take validators. if you want all the duplicates after the first to display an error, it is not so much of a problem.