I'd like to share with you a island solution I had to implement in ANTLR4.
Structure of the language. The language I had to write the grammar for is derived from
PL/SQL with some additional constructs. I won't go into more details here as this is off topic.
The language defines a special command PUT with the following structure:
PUT [<SPECIALISED LANGUAGE>].
My solution was:
Override Lexer's nextToken method:
public Token nextToken() {
if (f_current_idx != -1) {
_input.seek(f_current_idx); f_current_idx = -1;
}
Token l_token = super.nextToken(); return l_token;
}
Add some code in the Lexer:
PUT :
'PUT'
{
f_current_idx = _input.index(); ((ANTLRStringStream) _input).rewind();
SRC_PUTLexer l_put_lexer = new SRC_PUTLexer(_input);
UnbufferedTokenStream<Token> l_tokenStream = new UnbufferedTokenStream<Token>(l_put_lexer);
if (l_tokenStream.LA(2) == SRC_PUTLexer.LBRACK) {
new SRC_PUTParser(l_tokenStream).start_rule(); f_current_idx = _input.index();
}
};
Furthermore the class ANTLRStringStream which has disappeared in ANTLR 4 had to be defined:
public class ANTLRStringStream extends ANTLRInputStream {
protected int markDepth = 0;
protected int lastMarker;
protected ArrayList<Integer> markers;
public ANTLRStringStream() {
super();
}
public ANTLRStringStream(String input) {
super(input);
}
public int mark() {
if ( markers==null ) { markers = new ArrayList<Integer>(); }
markers.add(markDepth, index()); markDepth++; lastMarker = markDepth;
return markDepth;
}
public void rewind(int m) {
int state = (int) markers.get(m); seek(state); release(m);
}
public void rewind() { rewind(lastMarker); }
public void release(int marker) {
markDepth = marker; markDepth--;
}
}
Any feedback would be very welcome!
Kind regards, Wolfgang Hämmer
This should really be a community wiki.
My first major comment is you need to get rid of the ANTLRStringStream class. The ANTLRInputStream class provided by ANTLR 4 provides the functionality of ANTLRStringStream in ANTLR 3. The IntStream and CharStream interfaces were revised and extensively documented in ANTLR 4 to get rid of the problematic rewind methods and other undefined behavior. You should not reintroduce them.
Related
The application I'm working on has several places where we use AutoMapper to map entities.
The problem is if I had a model entity from one side to the other of the project, many times I forget to add the mapping for the new entity (I just need a copy paste from other entities), ending up that the solution compiles and I get no exception.
It just launches the application without full functionality and no debugging messages, which makes difficult to figure out what I've missed.
Is there any way to force the compiler at compile time to give me an error in case I forget to do a mapping?
AFAIK, there isn't a possibility to force compile-time checking for Automapper.
Nevertheless, there is a possibility to verify the correctness of your mappings:
After you've defined all your mappings, call the AssertConfigurationIsValid method which will throws an AutoMapperConfigurationException exception if the defined mappings are broken.
You can make this a part of your unit or integration test suite.
I had the same problem and decided to solve it by wrapping up AutoMapper. For each source-destination map I provide a method that I create after I've added it to my AutoMapper profile.
This may take away some of the ease of implementing AutoMapper but I find the compile time checking worth it.
public class MyType {
public string SomeProperty { get;set; }
}
public class MyOtherType {
public string SomeProperty { get;set; }
}
public class MyAlternateType {
public string AlternateProperty {get;set;}
}
public class AutoMapperProfile : Profile {
public AutoMapperProfile() {
CreateMap<MyType, MyOtherType>();
CreateMap<MyAlternateType, MyOtherType>()
.ForMember(ot => ot.SomeProperty, options => options.MapFrom(at => at.AlternateProperty));
}
}
public interface IMyMappingProvider {
// Uncomment below for Queryable Extensions
//IQueryable<TDestination> ProjectTo<TSource, TDestination>(IQueryable<TSource> source, params Expression<Func<TDestination, object>>[] membersToExpand);
//IQueryable<TDestination> ProjectTo<TSource, TDestination>(IQueryable<TSource> source, IDictionary<string, object> parameters, params string[] membersToExpand);
/*
* Add your mapping declarations below
*/
MyOtherType MapToMyOtherType(MyType source);
MyOtherType MapToMyOtherType(MyAlternateType source);
}
public class MyMappingProvider : IMyMappingProvider {
private IMapper Mapper { get; set; }
public MyMappingProvider(IMapper mapper) {
Mapper = mapper;
}
/* Uncomment this for Queryable Extensions
public IQueryable<TDestination> ProjectTo<TSource, TDestination>(IQueryable<TSource> source, params Expression<Func<TDestination, object>>[] membersToExpand) {
return new ProjectionExpression(source, Mapper.ConfigurationProvider.ExpressionBuilder).To<TDestination>(null, membersToExpand);
}
public IQueryable<TDestination> ProjectTo<TSource, TDestination>(IQueryable<TSource> source, IDictionary<string, object> parameters, params string[] membersToExpand) {
return new ProjectionExpression(source, Mapper.ConfigurationProvider.ExpressionBuilder).To<TDestination>(parameters, membersToExpand);
}
*/
/*
* Implement your mapping methods below
*/
public MyOtherType MapToMyOtherType(MyType source) {
return Mapper.Map<MyType, MyOtherType>(source);
}
public MyOtherType MapToMyOtherType(MyAlternateType source) {
return Mapper.Map<MyAlternateType, MyOtherType>(source);
}
}
If you are using the AutoMapper's Queryable extensions you can add the following class and uncomment the Queryable Extensions code above.
public static class QueryableExtensions {
/*
* Implement your extension methods below
*/
public static IQueryable<MyOtherType> ProjectToMyOtherType(this IQueryable<MyType> source, IMyMappingProvider mapper, params Expression<Func<MyOtherType, object>>[] membersToExpand)
{
return mapper.ProjectTo<MyType, MyOtherType>(source, membersToExpand);
}
public static IQueryable<MyOtherType> ProjectToMyOtherType(this IQueryable<MyAlternateType> source, IMyMappingProvider mapper, params Expression<Func<MyOtherType, object>>[] membersToExpand)
{
return mapper.ProjectTo<MyAlternateType, MyOtherType>(source, membersToExpand);
}
}
Tested with AutoMapper 6.1.1 using LinqPad:
var autoMapperConfig = new MapperConfiguration(cfg => { cfg.AddProfile(new AutoMapperProfile()); });
IMyMappingProvider mapper = new MyMappingProvider(autoMapperConfig.CreateMapper());
var myTypes = new List<MyType>()
{
new MyType() {SomeProperty = "Test1"},
new MyType() {SomeProperty = "Test2"},
new MyType() {SomeProperty = "Test3"}
};
myTypes.AsQueryable().ProjectToMyOtherType(mapper).Dump();
var myAlternateTypes = new List<MyAlternateType>()
{
new MyAlternateType() {AlternateProperty = "AlternateTest1"},
new MyAlternateType() {AlternateProperty = "AlternateTest2"},
new MyAlternateType() {AlternateProperty = "AlternateTest3"}
};
myAlternateTypes.AsQueryable().ProjectToMyOtherType(mapper).Dump();
mapper.MapToMyOtherType(myTypes[0]).Dump();
As #serge.karalenka said, don't forget to still test your mapping configuration by calling AssertConfigurationIsValid().
I try to understand how the lucene query syntax works so I wrote this small program.
When using a NumericRangeQuery I can find the documents I want but when trying to parse a search condition, it can't find any hits, although I'm using the same conditions.
i understand the difference can be explained by the analyzer but the StandardAnalyzer is used which does not remove numeric values.
Can someone tell me what I'm doing wrong ?
Thanks.
package org.burre.lucene.matching;
import java.io.IOException;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.*;
import org.apache.lucene.index.*;
import org.apache.lucene.queryparser.classic.ParseException;
import org.apache.lucene.queryparser.classic.QueryParser;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.NumericRangeQuery;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.store.*;
import org.apache.lucene.util.Version;
public class SmallestEngine {
private static final Version VERSION=Version.LUCENE_48;
private StandardAnalyzer analyzer = new StandardAnalyzer(VERSION);
private Directory index = new RAMDirectory();
private Document buildDoc(String name, int beds) {
Document doc = new Document();
doc.add(new StringField("name", name, Field.Store.YES));
doc.add(new IntField("beds", beds, Field.Store.YES));
return doc;
}
public void buildSearchEngine() throws IOException {
IndexWriterConfig config = new IndexWriterConfig(VERSION,
analyzer);
IndexWriter w = new IndexWriter(index, config);
// Generate 10 houses with 0 to 3 beds
for (int i=0;i<10;i++)
w.addDocument(buildDoc("house"+(100+i),i % 4));
w.close();
}
/**
* Execute the query and show the result
*/
public void search(Query q) throws IOException {
System.out.println("executing query\""+q+"\"");
IndexReader reader = DirectoryReader.open(index);
try {
IndexSearcher searcher = new IndexSearcher(reader);
ScoreDoc[] hits = searcher.search(q, 10).scoreDocs;
System.out.println("Found " + hits.length + " hits.");
for (int i = 0; i < hits.length; ++i) {
int docId = hits[i].doc;
Document d = searcher.doc(docId);
System.out.println(""+(i+1)+". " + d.get("name") + ", beds:"
+ d.get("beds"));
}
} finally {
if (reader != null)
reader.close();
}
}
public static void main(String[] args) throws IOException, ParseException {
SmallestEngine me = new SmallestEngine();
me.buildSearchEngine();
System.out.println("SearchByRange");
me.search(NumericRangeQuery.newIntRange("beds", 3, 3,true,true));
System.out.println("-----------------");
System.out.println("SearchName");
me.search(new QueryParser(VERSION,"name",me.analyzer).parse("house107"));
System.out.println("-----------------");
System.out.println("Search3Beds");
me.search(new QueryParser(VERSION,"beds",me.analyzer).parse("3"));
System.out.println("-----------------");
System.out.println("Search3BedsInRange");
me.search(new QueryParser(VERSION,"name",me.analyzer).parse("beds:[3 TO 3]"));
}
}
The output of this program is:
SearchByRange
executing query"beds:[3 TO 3]"
Found 2 hits.
1. house103, beds:3
2. house107, beds:3
-----------------
SearchName
executing query"name:house107"
Found 1 hits.
1. house107, beds:3
-----------------
Search3Beds
executing query"beds:3"
Found 0 hits.
-----------------
Search3BedsInRange
executing query"beds:[3 TO 3]"
Found 0 hits.
You need to use NumericRangeQuery to perform a search on the numeric field.
The answer here could give you some insight.
Also the answer here says
for numeric values (longs, dates, floats, etc.) you need to have NumericRangeQuery. Otherwise Lucene has no idea how do you want to define similarity.
What you need to do is to write your own QueryParser:
public class CustomQueryParser extends QueryParser {
// ctor omitted
#Override
public Query newTermQuery(Term term) {
if (term.field().equals("beds")) {
// manually construct and return non-range query for numeric value
} else {
return super.newTermQuery(term);
}
}
#Override
public Query newRangeQuery(String field, String part1, String part2, boolean startInclusive, boolean endInclusive) {
if (field.equals("beds")) {
// manually construct and return range query for numeric value
} else {
return super.newRangeQuery(field, part1, part2, startInclusive, endInclusive);
}
}
}
It seems like you always have to use the NumericRangeQuery for numeric conditions. (thanks to Mindas) so as he suggested I created My own more intelligent QueryParser.
Using the Apache commons-lang function StringUtils.isNumeric() I can create a more generic QueryParser:
public class IntelligentQueryParser extends QueryParser {
// take over super constructors
#Override
protected org.apache.lucene.search.Query newRangeQuery(String field,
String part1, String part2, boolean part1Inclusive, boolean part2Inclusive) {
if(StringUtils.isNumeric(part1))
{
return NumericRangeQuery.newIntRange(field, Integer.parseInt(part1),Integer.parseInt(part2),part1Inclusive,part2Inclusive);
}
return super.newRangeQuery(field, part1, part2, part1Inclusive, part2Inclusive);
}
#Override
protected org.apache.lucene.search.Query newTermQuery(
org.apache.lucene.index.Term term) {
if(StringUtils.isNumeric(term.text()))
{
return NumericRangeQuery.newIntRange(term.field(), Integer.parseInt(term.text()),Integer.parseInt(term.text()),true,true);
}
return super.newTermQuery(term);
}
}
Just wanted to share this.
I am creating a rule set engine that looks kinda like a unit test framework.
[RuleSet(ContextA)]
public class RuleSet1
{
[Rule(TargetingA)]
public Conclusion Rule1(SubjectA subject)
{ Create conclusion }
[Rule(TargetingA)]
public Conclusion Rule2(SubjectA subject)
{ Create conclusion }
[Rule(TargetingB)]
public Conclusion Rule3(SubjectB subject)
{ Create conclusion }
}
[RuleSet(ContextB)]
public class RuleSet2
{
[Rule(TargetingB)]
public Conclusion Rule1(SubjectB subject)
{ Create conclusion }
[Rule(TargetingA)]
public Conclusion Rule2(SubjectA subject)
{ Create conclusion }
[Rule(TargetingB)]
public Conclusion Rule3(SubjectB subject)
{ Create conclusion }
}
public class Conclusion()
{
// Errorcode, Description and such
}
// contexts and targeting info are enums.
The goal is to create an extensible ruleset that doesn't alter the API from consumer POV while having good separation-of-concerns within the code files. Again: like a unit test framework.
I am trying to create a library of these that expose the following API
public static class RuleEngine
{
public static IEnumerable<IRuleSet> RuleSets(contextFlags contexts)
{
{
return from type in Assembly.GetExecutingAssembly().GetTypes()
let attribute =
type.GetCustomAttributes(typeof (RuleSetAttribute), true)
.OfType<RuleSetAttribute>()
.FirstOrDefault()
where attribute != null
select ?? I don't know how to convert the individual methods to Func's.
}
}
}
internal interface IRuleset
{
IEnumerable<Func<SubjectA, Conclusion>> SubjectARules { get; }
IEnumerable<Func<SubjectB, Conclusion>> SubjectBRules { get; }
}
...which allows consumers to simply use like this (using foreach instead of LINQ for readability in this example)
foreach (var ruleset in RuleEgine.RuleSets(context))
{
foreach (var rule in ruleset.SubjectARules)
{
var conclusion = rule(myContextA);
//handle the conclusion
}
}
Also, it would be very helpful if you could tell me how to get rid of "TargetingA" and "TargetingB" as RuleAttribute parameters and instead use reflection to inspect the parameter type of the decorated method directly. All the while maintaining the same simple external API.
You can use Delegate.CreateDelegate and the GetParameters method to do what you want.
public class RuleSet : IRuleSet
{
public IEnumerable<Func<SubjectA, Conclusion>> SubjectARules { get; set; }
public IEnumerable<Func<SubjectB, Conclusion>> SubjectBRules { get; set; }
}
public static class RuleEngine
{
public static IEnumerable<IRuleSet> RuleSets() // removed contexts parameter for brevity
{
var result = from t in Assembly.GetExecutingAssembly().GetTypes()
where t.GetCustomAttributes(typeof(RuleSetAttribute), true).Any()
let m = t.GetMethods().Where(m => m.GetCustomAttributes(typeof(RuleAttribute)).Any()).ToArray()
select new RuleSet
{
SubjectARules = CreateFuncs<SubjectA>(m).ToList(),
SubjectBRules = CreateFuncs<SubjectB>(m).ToList()
};
return result;
}
}
// no error checking for brevity
// TODO: use better variable names
public static IEnumerable<Func<T, Conclusion>> CreateFuncs<T>(MethodInfo[] m)
{
return from x in m
where x.GetParameters()[0].ParameterType == typeof(T)
select (Func<T, Conclusion>)Delegate.CreateDelegate(typeof(Func<T, Conclusion>), null, x);
}
Then you can use it like this:
var sa = new SubjectA();
foreach (var ruleset in RuleEngine.RuleSets())
{
foreach (var rule in ruleset.SubjectARules)
{
var conclusion = rule(sa);
// do something with conclusion
}
}
In your LINQ query you headed straight for RuleSetAttribute, and so lost other information. If you break the query in several lines of code you can get methods from the type with GetMethods(), and then you can call GetCustomAttribute<RuleAttribute>().
Given a EF-Code First CTP5 entity layout like:
public class Person { ... }
which has a collection of:
public class Address { ... }
which has a single association of:
public class Mailbox { ... }
I want to do:
PersonQuery.Include(x => x.Addresses).Include("Addresses.Mailbox")
WITHOUT using a magic string. I want to do it using a lambda expression.
I am aware what I typed above will compile and will bring back all Persons matching the search criteria with their addresses and each addresses' mailbox eager loaded, but it's in a string which irritates me.
How do I do it without a string?
Thanks Stack!
For that you can use the Select method:
PersonQuery.Include(x => x.Addresses.Select(a => a.Mailbox));
You can find other examples in here and here.
For any one thats still looking for a solution to this, the Lambda includes is part of EF 4+ and it is in the System.Data.Entity namespace; examples here
http://romiller.com/2010/07/14/ef-ctp4-tips-tricks-include-with-lambda/
It is described in this post: http://www.thomaslevesque.com/2010/10/03/entity-framework-using-include-with-lambda-expressions/
Edit (By Asker for readability):
The part you are looking for is below:
public static class ObjectQueryExtensions
{
public static ObjectQuery<T> Include<T>(this ObjectQuery<T> query, Expression<Func<T, object>> selector)
{
string path = new PropertyPathVisitor().GetPropertyPath(selector);
return query.Include(path);
}
class PropertyPathVisitor : ExpressionVisitor
{
private Stack<string> _stack;
public string GetPropertyPath(Expression expression)
{
_stack = new Stack<string>();
Visit(expression);
return _stack
.Aggregate(
new StringBuilder(),
(sb, name) =>
(sb.Length > 0 ? sb.Append(".") : sb).Append(name))
.ToString();
}
protected override Expression VisitMember(MemberExpression expression)
{
if (_stack != null)
_stack.Push(expression.Member.Name);
return base.VisitMember(expression);
}
protected override Expression VisitMethodCall(MethodCallExpression expression)
{
if (IsLinqOperator(expression.Method))
{
for (int i = 1; i < expression.Arguments.Count; i++)
{
Visit(expression.Arguments[i]);
}
Visit(expression.Arguments[0]);
return expression;
}
return base.VisitMethodCall(expression);
}
private static bool IsLinqOperator(MethodInfo method)
{
if (method.DeclaringType != typeof(Queryable) && method.DeclaringType != typeof(Enumerable))
return false;
return Attribute.GetCustomAttribute(method, typeof(ExtensionAttribute)) != null;
}
}
}
I was just trying to code the following extension method:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace _4Testing
{
static class ExtensionMethods
{
public static void AssignMe(this int me, int value)
{
me = value;
}
}
}
But it is not working, i mean, can I use an extension method to alter values from extended classes? I don't want to change void return type to int, just changing extended class value. Thanks in advance
Your example uses int, which is a value type. Classes are reference types and behaves a bit differently in this case.
While you could make a method that takes another reference like AssignMe(this MyClass me, MyClass other), the method would work on a copy of the reference, so if you assign other to me it would only affect the local copy of the reference.
Also, keep in mind that extension methods are just static methods in disguise. I.e. they can only access public members of the extended types.
public sealed class Foo {
public int PublicValue;
private int PrivateValue;
}
public static class FooExtensions {
public static void Bar(this Foo f) {
f.PublicValue = 42;
// Doesn't compile as the extension method doesn't have access to Foo's internals
f.PrivateValue = 42;
}
}
// a work around for extension to a wrapping reference type is following ....
using System;
static class Program
{
static void Main(string[] args)
{
var me = new Integer { value = 5 };
int y = 2;
me.AssignMe(y);
Console.WriteLine(me); // prints 2
Console.ReadLine();
}
public static void AssignMe(this Integer me, int value)
{
me.value = value;
}
}
class Integer
{
public int value { get; set; }
public Integer()
{
value = 0;
}
public override string ToString()
{
return value.ToString();
}
}
Ramon what you really need is a ref modifier on the first (i.e. int me ) parameter of the extension method, but C# does not allow ref modifier on parameters having 'this' modifiers.
[Update]
No workaround should be possible for your particular case of an extension method for a value type. Here is the "reductio ad absurdum" that you are asking for if you are allowed to do what you want to do; consider the C# statement:
5.AssignMe(10);
... now what on earth do you think its suppose to do ? Are you trying to assign 10 to 5 ??
Operator overloading cannot help you either.
This is an old post but I ran into a similar problem trying to implement an extender for the String class.
My original code was this:
public static void Revert(this string s)
{
char[] xc = s.ToCharArray();
s = new string(xc.Reverse());
}
By using the new keyword I am creating a new object and since s is not passed by reference it will not be modified.
I changed it to the following which provides a solution to Ramon's problem:
public static string Reverse(this string s)
{
char[] xc = s.ToCharArray();
Array.Reverse(xc);
return new string(xc);
}
In which case the calling code will be:
s = s.Reverse();
To manipulate integers you can do something like:
public static int Increment(this int i)
{
return i++;
}
i = i.Increment();