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  • Repository Pattern with Entity Framework 3.5

    - by Ravi
    I am developing a Database File System. I am using - .Net framework 3.5 Entity Framework 3.5 WPF with MVVM pattern The project spans across multiple assemblies each using same model. One assembly,let's call it a "server", only adds data to the database using EF i.e. same model.Other assemblies (including the UI) both reads and writes the data.The changes made by server should immediately reflect in other assemblies. The database contains self referencing tables where each entity can have single OR no parent and (may be) some children. I want to use repository pattern which can also provide some mechanism to handle this hierarchical nature. I have already done reading on this on Code Project. It shares the same context(entities) everywhere. My question is - Should I share the same context everywhere? What are the advantages and disadvantages of doing that?

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  • when to use the abstract factory pattern?

    - by hguser
    Hi: I want to know when we need to use the abstract factory pattern. Here is an example,I want to know if it is necessary. The UML THe above is the abstract factory pattern, it is recommended by my classmate. THe following is myown implemention. I do not think it is necessary to use the pattern. And the following is some core codes: package net; import java.io.IOException; import java.util.HashMap; import java.util.Map; import java.util.Properties; public class Test { public static void main(String[] args) throws IOException, InstantiationException, IllegalAccessException, ClassNotFoundException { DaoRepository dr=new DaoRepository(); AbstractDao dao=dr.findDao("sql"); dao.insert(); } } class DaoRepository { Map<String, AbstractDao> daoMap=new HashMap<String, AbstractDao>(); public DaoRepository () throws IOException, InstantiationException, IllegalAccessException, ClassNotFoundException { Properties p=new Properties(); p.load(DaoRepository.class.getResourceAsStream("Test.properties")); initDaos(p); } public void initDaos(Properties p) throws InstantiationException, IllegalAccessException, ClassNotFoundException { String[] daoarray=p.getProperty("dao").split(","); for(String dao:daoarray) { AbstractDao ad=(AbstractDao)Class.forName(dao).newInstance(); daoMap.put(ad.getID(),ad); } } public AbstractDao findDao(String id) {return daoMap.get(id);} } abstract class AbstractDao { public abstract String getID(); public abstract void insert(); public abstract void update(); } class SqlDao extends AbstractDao { public SqlDao() {} public String getID() {return "sql";} public void insert() {System.out.println("sql insert");} public void update() {System.out.println("sql update");} } class AccessDao extends AbstractDao { public AccessDao() {} public String getID() {return "access";} public void insert() {System.out.println("access insert");} public void update() {System.out.println("access update");} } And the content of the Test.properties is just one line: dao=net.SqlDao,net.SqlDao So any ont can tell me if this suitation is necessary?

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  • Variable 'app' in url-pattern for servlet mapping

    - by Brian
    I'm learning Spring MVC (and servlets in general) and following springsource's mvc-ajax example, which uses annotated controller methods. It appears that there is only one url-pattern (in web.xml) mapped to a servlet in that example: /app/* I've deployed the app as a WAR file, and the actual, ugly URL I'm requesting is http://127.0.0.1:8080/org.springframework.samples.mvc.ajax-1.0.0-20100407.233245-1/account. So, it appears that 'app' in '/app/*' is a variable corresponding to 'org.springframework.samples.mvc.ajax-1.0.0-20100407.233245-1', however, it isn't universal because it isn't usable in my own app, and it contradicts my understanding that url-pattern contains the portion of the URL after the app name. So, what is 'app'? Where is it configured?

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  • Understanding pattern matching with cons operator

    - by Mathias
    In "Programming F#" I came across a pattern-matching like this one (I simplified a bit): let rec len list = match list with | [] -> 0 | [_] -> 1 | head :: tail -> 1 + len tail;; Practically, I understand that the last match recognizes the head and tail of the list. Conceptually, I don't get why it works. As far as I understand, :: is the cons operator, which appends a value in head position of a list, but it doesn't look to me like it is being used as an operator here. Should I understand this as a "special syntax" for lists, where :: is interpreted as an operator or a "match pattern" depending on context? Or can the same idea be extended for types other than lists, with other operators?

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  • When to use the Flyweight Pattern

    - by elmt
    So I've just gotten on the boost train and was checking out the flyweight pattern and was interested in implementing it in my project. Obviously, it doesn't make sense to use it on any class that has only has one instance of it. However, say I have 5 instances of an class. Should I be using the flyweight pattern or should it be only used for a class that has at least N instances. I realize that many factors will influence this answer (how many fields there are, the size of the fields, etc.).

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  • Better to use constructor or method factory pattern?

    - by devoured elysium
    I have a wrapper class for the Bitmap .NET class called BitmapZone. Assuming we have a WIDTH x HEIGHT bitmap picture, this wrapper class should serve the purpose of allowing me to send to other methods/classes itself instead of the original bitmap. I can then better control what the user is or not allowed to do with the picture (and I don't have to copy the bitmap lots of times to send for each method/class). My question is: knowing that all BitmapZone's are created from a Bitmap, what do you find preferrable? Constructor syntax: something like BitmapZone bitmapZone = new BitmapZone(originalBitmap, x, y, width, height); Factory Method Pattern: BitmapZone bitmapZone = BitmapZone.From(originalBitmap, x , y, width, height); Factory Method Pattern: BitmapZone bitmapZone = BitmapZone.FromBitmap(originalBitmap, x, y, width, height); Other? Why? Thanks

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  • Problem with literal arguments in the PATTERN string for a python 2to3 fixer

    - by Zxaos
    Hi folks. I'm writing a fixer for the 2to3 tool in python. In my pattern string, I have a section where I'd like to match an empty string as an argument, or an empty unicode string. The relevant chunk of my pattern looks like: (args='""' | args='u""') My issue is the second option never matches. Even if it's alone, it won't match. However, if I simply say args=any and then output args, I can catch cases where args is exactly equal to the second option. Is there some weird unicode handling thing going on? Why won't the second literal option ever match?

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  • Combination of Operating Mode and Commit Strategy

    - by Kevin Yang
    If you want to populate a source into multiple targets, you may also want to ensure that every row from the source affects all targets uniformly (or separately). Let’s consider the Example Mapping below. If a row from SOURCE causes different changes in multiple targets (TARGET_1, TARGET_2 and TARGET_3), for example, it can be successfully inserted into TARGET_1 and TARGET_3, but failed to be inserted into TARGET_2, and the current Mapping Property TLO (target load order) is “TARGET_1 -> TARGET_2 -> TARGET_3”. What should Oracle Warehouse Builder do, in order to commit the appropriate data to all affected targets at the same time? If it doesn’t behave as you intended, the data could become inaccurate and possibly unusable.                                               Example Mapping In OWB, we can use Mapping Configuration Commit Strategies and Operating Modes together to achieve this kind of requirements. Below we will explore the combination of these two features and how they affect the results in the target tables Before going to the example, let’s review some of the terms we will be using (Details can be found in white paper Oracle® Warehouse Builder Data Modeling, ETL, and Data Quality Guide11g Release 2): Operating Modes: Set-Based Mode: Warehouse Builder generates a single SQL statement that processes all data and performs all operations. Row-Based Mode: Warehouse Builder generates statements that process data row by row. The select statement is in a SQL cursor. All subsequent statements are PL/SQL. Row-Based (Target Only) Mode: Warehouse Builder generates a cursor select statement and attempts to include as many operations as possible in the cursor. For each target, Warehouse Builder inserts each row into the target separately. Commit Strategies: Automatic: Warehouse Builder loads and then automatically commits data based on the mapping design. If the mapping has multiple targets, Warehouse Builder commits and rolls back each target separately and independently of other targets. Use the automatic commit when the consequences of multiple targets being loaded unequally are not great or are irrelevant. Automatic correlated: It is a specialized type of automatic commit that applies to PL/SQL mappings with multiple targets only. Warehouse Builder considers all targets collectively and commits or rolls back data uniformly across all targets. Use the correlated commit when it is important to ensure that every row in the source affects all affected targets uniformly. Manual: select manual commit control for PL/SQL mappings when you want to interject complex business logic, perform validations, or run other mappings before committing data. Combination of the commit strategy and operating mode To understand the effects of each combination of operating mode and commit strategy, I’ll illustrate using the following example Mapping. Firstly we insert 100 rows into the SOURCE table and make sure that the 99th row and 100th row have the same ID value. And then we create a unique key constraint on ID column for TARGET_2 table. So while running the example mapping, OWB tries to load all 100 rows to each of the targets. But the mapping should fail to load the 100th row to TARGET_2, because it will violate the unique key constraint of table TARGET_2. With different combinations of Commit Strategy and Operating Mode, here are the results ¦ Set-based/ Correlated Commit: Configuration of Example mapping:                                                     Result:                                                      What’s happening: A single error anywhere in the mapping triggers the rollback of all data. OWB encounters the error inserting into Target_2, it reports an error for the table and does not load the row. OWB rolls back all the rows inserted into Target_1 and does not attempt to load rows to Target_3. No rows are added to any of the target tables. ¦ Row-based/ Correlated Commit: Configuration of Example mapping:                                                   Result:                                                  What’s happening: OWB evaluates each row separately and loads it to all three targets. Loading continues in this way until OWB encounters an error loading row 100th to Target_2. OWB reports the error and does not load the row. It rolls back the row 100th previously inserted into Target_1 and does not attempt to load row 100 to Target_3. Then, if there are remaining rows, OWB will continue loading them, resuming with loading rows to Target_1. The mapping completes with 99 rows inserted into each target. ¦ Set-based/ Automatic Commit: Configuration of Example mapping: Result: What’s happening: When OWB encounters the error inserting into Target_2, it does not load any rows and reports an error for the table. It does, however, continue to insert rows into Target_3 and does not roll back the rows previously inserted into Target_1. The mapping completes with one error message for Target_2, no rows inserted into Target_2, and 100 rows inserted into Target_1 and Target_3 separately. ¦ Row-based/Automatic Commit: Configuration of Example mapping: Result: What’s happening: OWB evaluates each row separately for loading into the targets. Loading continues in this way until OWB encounters an error loading row 100 to Target_2 and reports the error. OWB does not roll back row 100th from Target_1, does insert it into Target_3. If there are remaining rows, it will continue to load them. The mapping completes with 99 rows inserted into Target_2 and 100 rows inserted into each of the other targets. Note: Automatic Correlated commit is not applicable for row-based (target only). If you design a mapping with the row-based (target only) and correlated commit combination, OWB runs the mapping but does not perform the correlated commit. In set-based mode, correlated commit may impact the size of your rollback segments. Space for rollback segments may be a concern when you merge data (insert/update or update/insert). Correlated commit operates transparently with PL/SQL bulk processing code. The correlated commit strategy is not available for mappings run in any mode that are configured for Partition Exchange Loading or that include a Queue, Match Merge, or Table Function operator. If you want to practice in your own environment, you can follow the steps: 1. Import the MDL file: commit_operating_mode.mdl 2. Fix the location for oracle module ORCL and deploy all tables under it. 3. Insert sample records into SOURCE table, using below plsql code: begin     for i in 1..99     loop         insert into source values(i, 'col_'||i);     end loop;     insert into source values(99, 'col_99'); end; 4. Configure MAPPING_1 to any combinations of operating mode and commit strategy you want to test. And make sure feature TLO of mapping is open. 5. Deploy Mapping “MAPPING_1”. 6. Run the mapping and check the result.

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  • Matching Line Boundaries in a Regular Expression (Pattern.MULTILINE/(?m)) is broken in Java?

    - by Mister M. Bean
    The example on http://www.exampledepot.com/egs/java.util.regex/Line.html gives false for me twice but should'nt! Why? CharSequence inputStr = "abc\ndef"; String patternStr = "abc$"; // Compile with multiline enabled Pattern pattern = Pattern.compile(patternStr, Pattern.MULTILINE); Matcher matcher = pattern.matcher(inputStr); boolean matchFound = matcher.find(); // true // Use an inline modifier to enable multiline mode matchFound = pattern.matches(".*abc$.*", "abc\r\ndef"); // false System.out.println(matchFound); // false matchFound = pattern.matches("(?m).*abc$.*", "abc\r\ndef"); // true System.out.println(matchFound);// false !!!!!

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  • sed find pattern on line with another pattern

    - by user2962390
    I am trying to extract text from a file between a '<' and a '', but only on a line starting with another specific pattern. So in a file that looks like: XXX Something here XXX Something more here XXX <\Lines like this are a problem ZZZ something <\This is the text I need XXX Don't need any of this I would like to print only the "<\This is the text I need". If I do sed -n '/^ZZZ/p' FILENAME it pulls the correct lines I need to look at, but obviously prints the whole line. sed -n '/</,//p' FILENAME prints way too much. I have looked into grouping and tried sed -n '/^ZZZ/{/</,//} FILENAME but this doesn't seem to work at all. Any suggestions? They will be much appreciated. (Apologies for formatting, never posted on here before)

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  • Data structure for pattern matching.

    - by alvonellos
    Let's say you have an input file with many entries like these: date, ticker, open, high, low, close, <and some other values> And you want to execute a pattern matching routine on the entries(rows) in that file, using a candlestick pattern, for example. (See, Doji) And that pattern can appear on any uniform time interval (let t = 1s, 5s, 10s, 1d, 7d, 2w, 2y, and so on...). Say a pattern matching routine can take an arbitrary number of rows to perform an analysis and contain an arbitrary number of subpatterns. In other words, some patterns may require 4 entries to operate on. Say also that the routine (may) later have to find and classify extrema (local and global maxima and minima as well as inflection points) for the ticker over a closed interval, for example, you could say that a cubic function (x^3) has the extrema on the interval [-1, 1]. (See link) What would be the most natural choice in terms of a data structure? What about an interface that conforms a Ticker object containing one row of data to a collection of Ticker so that an arbitrary pattern can be applied to the data. What's the first thing that comes to mind? I chose a doubly-linked circular linked list that has the following methods: push_front() push_back() pop_front() pop_back() [] //overloaded, can be used with negative parameters But that data structure seems very clumsy, since so much pushing and popping is going on, I have to make a deep copy of the data structure before running an analysis on it. So, I don't know if I made my question very clear -- but the main points are: What kind of data structures should be considered when analyzing sequential data points to conform to a pattern that does NOT require random access? What kind of data structures should be considered when classifying extrema of a set of data points?

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  • Name for Osherove's modified singleton pattern?

    - by Kazark
    I'm pretty well sold on the "singletons are evil" line of thought. Nevertheless, there are limited occurrences when you want to limit the creation of an object. Roy Osherove advises, If you're planning to use a singleton in your design, separate the logic of the singleton class and the logic that makes it a singleton (the part that initializes a static variables, for example) into two separate classes. That way, you can keep the single responsibility principle (SRP) and also have a way to override singleton logic. (The Art of Unit Testing 261-262) This pattern still perpetuates the global state. However, it does result in a testable design, so it seems to me to be a good pattern for mitigating the damage of a singleton. However, Osherove does not give a name to this pattern; but naming a pattern, according to the Gang of Four, is important: Naming a pattern immediately increases our design vocabulary. It lets us design at a higher level of abstraction. (3) Is there a standard name for this pattern? It seems different enough from a standard singleton to deserve a separate name. Decoupled Singleton, perhaps?

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  • LUA: A couple of pattern matching issues

    - by Josh
    I'm fairly new to lua programming, but I'm also a quick study. I've been working on a weather forecaster for a program that I use, and it's working well, for the most part. Here is what I have so far. (Pay no attention to the zs.stuff. That is program specific and has no bearing on the lua coding.) if not http then http = require("socket.http") end local locale = string.gsub(zs.params(1),"%s+","%%20") local page = http.request("http://www.wunderground.com/cgi-bin/findweather/getForecast?query=" .. locale .. "&wuSelect=WEATHER") local location = string.match(page,'title="([%w%s,]+) RSS"') --print("Gathering weather information for " .. location .. ".") --local windspeed = string.match(page,'<span class="nobr"><span class="b">([%d.]+)</span>&nbsp;mph</span>') --print(windspeed) local condition = string.match(page, '<td class="vaM taC"><img src="http://icons-ecast.wxug.com/i/c/a/[%w_]+.gif" width="42" height="42" alt="[%w%s]+" class="condIcon" />') --local image = string.match(page, '<img src="http://icons-ecast.wxug.com/i/c/a/(.+).gif" width="42" height="42" alt="[%w%s]+" class="condIcon" />') local temperature = string.match(page,'pwsvariable="tempf" english="&deg;F" metric="&deg;C" value="([%d.]+)">') local humidity = string.match(page,'pwsvariable="humidity" english="" metric="" value="(%d+)"') zs.say(location) --zs.say("image ./Images/" .. image .. ".gif") zs.say("<color limegreen>Condition:</color> <color white>" .. condition .. "</color>") zs.say("<color limegreen>Temperature: </color><color white>" .. temperature .. "F</color>") zs.say("<color limegreen>Humidity: </color><color white>" .. humidity .. "%</color>") My main issue is this: I changed the 'condition' and added the 'image' variables to what they are now. Even though the line it's supposed to be matching comes directly from the webpage, it fails to match at all. So I'm wondering what it is I'm missing that's preventing this code from working. If I take out the <td class="vaM taC">< img src="http://icons-ecast.wxug.com/i/c/a/[%w_]+.gif" it'll match condition flawlessly. (For whatever reason, I can't get the above line to display correctly, but there is no space between the `< and img) Can anyone point out what is wrong with it? Aside from the pattern matching, I assure you the line is verbatim from the webpage. Another question I had is the ability to match across line breaks. Is there any possible way to do this? The reason why I ask is because on that same page, a few of the things I need to match are broken up on separate lines, and since the actual pattern I'm wanting to match shows up in other places on the page, I need to be able to match across line breaks to get the exact pattern. I appreciate any help in this matter!

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  • Sharding / indexing strategy for multi-faceted search

    - by Graham
    I'm currently thinking about our database structure and how we modify it for scale. Specifically, we're thinking about using ElasticSearch to provide our search functionality. One common pattern with ElasticSearch seems to be the 'user-routing' pattern; that is, using routing to ensure that any one user's data resides on the same shard. This is great for client-specific search e.g. Gmail. Our application has a constraint such that any user will have a maximum of a few thousand documents, so this pattern seems like a good candidate. However, our search needs to work across all users, as well as targeting a specific user (so I might search my content, Alice's content, or all content). Similarly, we need to provide full-text search across any timeframe; recent months to several years ago. I'm thinking of combining the 'user-routing' and 'index-per-time-interval' patterns: I create an index for each month By default, searches are aliased against the most recent X months If no results are found, we can search against previous X months As we grow, we can reduce the interval X Each document is routed by the user ID So, this should let us do the following: search by user. This will search all indeces across 1 shard search by time. This will search ~2 indeces (by default) across all shards Is this a reasonable approach, considering we may scale to multi-million+ documents? Or should I be denormalizing the data somehow, so that user searches are performed on a totally seperate index from date searches? Thanks for any pros-cons of the above scenario.

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  • Linq to SQL and concurrency with Rob Conery repository pattern

    - by David Hall
    I have implemented a DAL using Rob Conery's spin on the repository pattern (from the MVC Storefront project) where I map database objects to domain objects using Linq and use Linq to SQL to actually get the data. This is all working wonderfully giving me the full control over the shape of my domain objects that I want, but I have hit a problem with concurrency that I thought I'd ask about here. I have concurrency working but the solution feels like it might be wrong (just one of those gitchy feelings). The basic pattern is: private MyDataContext _datacontext private Table _tasks; public Repository(MyDataContext datacontext) { _dataContext = datacontext; } public void GetTasks() { _tasks = from t in _dataContext.Tasks; return from t in _tasks select new Domain.Task { Name = t.Name, Id = t.TaskId, Description = t.Description }; } public void SaveTask(Domain.Task task) { Task dbTask = null; // Logic for new tasks omitted... dbTask = (from t in _tasks where t.TaskId == task.Id select t).SingleOrDefault(); dbTask.Description = task.Description, dbTask.Name = task.Name, _dataContext.SubmitChanges(); } So with that implementation I've lost concurrency tracking because of the mapping to the domain task. I get it back by storing the private Table which is my datacontext list of tasks at the time of getting the original task. I then update the tasks from this stored Table and save what I've updated This is working - I get change conflict exceptions raised when there are concurrency violations, just as I want. However, it just screams to me that I've missed a trick. Is there a better way of doing this? I've looked at the .Attach method on the datacontext but that appears to require storing the original version in a similar way to what I'm already doing. I also know that I could avoid all this by doing away with the domain objects and letting the Linq to SQL generated objects all the way up my stack - but I dislike that just as much as I dislike the way I'm handling concurrency.

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  • preg_match , pattern, php

    - by Michael
    I'm trying to extract some specific pictures from html content . Currently I have the following array [1] = Array ( [0] = BuEZm5g!Wk~$(KGrHqQH-DgEvrb2CLuOBL-vbkHlKw~~_14.JPG#!BuEZm5g!Wk~$(KGrHqQH-DgEvrb2CLuOBL-vbkHlKw~~_12.JPG|1#http://i.ebayimg.com/08#!BuEZqMQBGk~$(KGrHqQH-DoEvrKYSoPiBL-vb)WgLw~~_14.JPG#!BuEZqMQBGk~$(KGrHqQH-DoEvrKYSoPiBL-vb)WgLw~~_12.JPG|2#http://i.ebayimg.com/13#!BuEZtkw!2k~$(KGrHqYH-EYEvsh4EjJSBL-vb-bLow~~_14.JPG#!BuEZtkw!2k~$(KGrHqYH-EYEvsh4EjJSBL-vb-bLow~~_12.JPG|3#http://i.ebayimg.com/03#!BuEZ)!wEGk~$(KGrHqYH-DwEvq8Z1JuQBL-vcMOoFQ~~_14.JPG#!BuEZ)!wEGk~$(KGrHqYH-DwEvq8Z1JuQBL-vcMOoFQ~~_12.JPG|4#http://i.ebayimg.com/09#!BuEZ1IQEGk~$(KGrHqEH-D0EvqwClvviBL-vcclJwg~~_14.JPG#!BuEZ1IQEGk~$(KGrHqEH-D0EvqwClvviBL-vcclJwg~~_12.JPG|5#http://i.ebayimg.com/17#!BuEZ4FQCWk~$(KGrHqUH-DMEvS+,FRj5BL-vco)Qgg~~_14.JPG#!BuEZ4FQCWk~$(KGrHqUH-DMEvS+,FRj5BL-vco)Qgg~~_12.JPG|6#http://i.ebayimg.com/17#!BuEZ7FQEWk~$(KGrHqYH-EYEvsh4EjJSBL-vc1v2Hg~~_14.JPG#!BuEZ7FQEWk~$(KGrHqYH-EYEvsh4EjJSBL-vc1v2Hg~~_12.JPG|7#http://i.ebayimg.com/12#!BuEZ-c!Bmk~$(KGrHqQH-CYEvr5z9)NVBL-vdC,)Mg~~_14.JPG#!BuEZ-c!Bmk~$(KGrHqQH-CYEvr5z9)NVBL-vdC,)Mg~~_12.JPG|8#http://i.ebayimg.com/20#!BuE,CNgCWk~$(KGrHqIH-CIEvqKBurmhBL-vdRBe3!~~_14.JPG#!BuE,CNgCWk~$(KGrHqIH-CIEvqKBurmhBL-vdRBe3!~~_12.JPG|9#http://i.ebayimg.com/24#!BuE,FN!EWk~$(KGrHqUH-C0EvsBdjbv0BL-vdeFkD!~~_14.JPG#!BuE,FN!EWk~$(KGrHqUH-C0EvsBdjbv0BL-vdeFkD!~~_12.JPG|10#http://i.ebayimg.com/16#!BuE,IOgBmk~$(KGrHqEH-EMEvpym7mSLBL-vdqI6nw~~_14.JPG#!BuE,IOgBmk~$(KGrHqEH-EMEvpym7mSLBL-vdqI6nw~~ ) I need to extract only the pictures that start with ! and ends in 12.JPG . An example of expected result is !BuEZm5g!Wk~$(KGrHqQH-DgEvrb2CLuOBL-vbkHlKw~~_12.JPG . I have a pattern but it doesn't work for some reasons that I don't know . It is $pattern = "/#\!(.*)_12.JPG/"; Thank you in advance for any help

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  • Database migration pattern for Java?

    - by Eno
    Im working on some database migration code in Java. Im also using a factory pattern so I can use different kinds of databases. And each kind of database im using implements a common interface. What I would like to do is have a migration check that is internal to the class and runs some database schema update code automatically. The actual update is pretty straight forward (I check schema version in a table and compare against a constant in my app to decide whether to migrate or not and between which versions of schema). To make this automatic I was thinking the test should live inside (or be called from) the constructor. OK, fair enough, that's simple enough. My problem is that I dont want the test to run every single time I instantiate a database object (it runs a query so having it run on every construction is not efficient). So maybe this should be a class static method? I guess my question is, what is a good design pattern for this type of problem? There ought to be a clean way to ensure the migration test runs only once OR is super-efficient.

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  • Need help make these classes use Visitor Pattern and generics

    - by Shervin
    Hi. I need help to generify and implement the visitor pattern. We are using tons of instanceof and it is a pain. I am sure it can be modified, but I am not sure how to do it. Basically we have an interface ProcessData public interface ProcessData { public setDelegate(Object delegate); public Object getDelegate(); //I am sure these delegate methods can use generics somehow } Now we have a class ProcessDataGeneric that implements ProcessData public class ProcessDataGeneric implements ProcessData { private Object delegate; public ProcessDataGeneric(Object delegate) { this.delegate = delegate; } } Now a new interface that retrieves the ProcessData interface ProcessDataWrapper { public ProcessData unwrap(); } Now a common abstract class that implements the wrapper so ProcessData can be retrieved @XmlSeeAlso( { ProcessDataMotorferdsel.class,ProcessDataTilskudd.class }) public abstract class ProcessDataCommon implements ProcessDataWrapper { protected ProcessData unwrapped; public ProcessData unwrap() { return unwrapped; } } Now the implementation public class ProcessDataMotorferdsel extends ProcessDataCommon { public ProcessDataMotorferdsel() { unwrapped = new ProcessDataGeneric(this); } } similarly public class ProcessDataTilskudd extends ProcessDataCommon { public ProcessDataTilskudd() { unwrapped = new ProcessDataGeneric(this); } } Now when I use these classes, I always need to do instanceof ProcessDataCommon pdc = null; if(processData.getDelegate() instanceof ProcessDataMotorferdsel) { pdc = (ProcessDataMotorferdsel) processData.getDelegate(); } else if(processData.getDelegate() instanceof ProcessDataTilskudd) { pdc = (ProcessDataTilskudd) processData.getDelegate(); } I know there is a better way to do this, but I have no idea how I can utilize Generics and the Visitor Pattern. Any help is GREATLY appreciated.

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  • JavaScript Module Pattern - What about using "return this"?

    - by Rob
    After doing some reading about the Module Pattern, I've seen a few ways of returning the properties which you want to be public. One of the most common ways is to declare your public properties and methods right inside of the "return" statement, apart from your private properties and methods. A similar way (the "Revealing" pattern) is to provide simply references to the properties and methods which you want to be public. Lastly, a third technique I saw was to create a new object inside your module function, to which you assign your new properties before returning said object. This was an interesting idea, but requires the creation of a new object. So I was thinking, why not just use "this.propertyName" to assign your public properties and methods, and finally use "return this" at the end? This way seems much simpler to me, as you can create private properties and methods with the usual "var" or "function" syntax, or use the "this.propertyName" syntax to declare your public methods. Here's the method I'm suggesting: (function() { var privateMethod = function () { alert('This is a private method.'); } this.publicMethod = function () { alert('This is a public method.'); } return this; })(); Are there any pros/cons to using the method above? What about the others?

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  • Scheme: Mysterious void in pattern match.

    - by Schemer
    Hi. I am writing a function called annotate that uses match-lambda -- often with recursive calls to annotate. Here is one of the pattern matches: (`(lambda (,<param1> . ,<params>) ,<stmts>) `(CLOSURE ENV (,<param1> . ,<params>) (lambda (ENV) ,(map annotate (map (lambda (x) (append `(,<param1> . ,<params>) (list x))) `(,<stmts>)))))) However, when this pattern is matched this is what returns: '(CLOSURE ENV (x) (lambda (ENV) ((CLOSURE ENV (x y) (lambda (ENV) ((+ x y)))))) #<void>) Specifically I can't figure out where "void" is coming from. In fact, if I include the line: ,(displayln (map annotate (map (lambda (x) (append `(,<param1> . ,<params>) (list x))) `(,<stmts>)))) it prints: ((CLOSURE ENV (x y) (lambda (ENV) ((+ x y))))) notably without "void". If someone could tell me what the problem is it would be greatly appreciated. Thanks.

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  • Repository Pattern Standardization of methods

    - by Nix
    All I am trying to find out the correct definition of the repository pattern. My original understanding was this (extremely dubmed down) Separate your Business Objects from your Data Objects Standardize access methods in data access layer. I have really seen 2 different implementations. Implementation 1 : public Interface IRepository<T>{ List<T> GetAll(); void Create(T p); void Update(T p); } public interface IProductRepository: IRepository<Product> { //Extension methods if needed List<Product> GetProductsByCustomerID(); } Implementation 2 : public interface IProductRepository { List<Product> GetAllProducts(); void CreateProduct(Product p); void UpdateProduct(Product p); List<Product> GetProductsByCustomerID(); } Notice the first is generic Get/Update/GetAll, etc, the second is more of what I would define "DAO" like. Both share an extraction from your data entities. Which I like, but i can do the same with a simple DAO. However the second piece standardize access operations I see value in, if you implement this enterprise wide people would easily know the set of access methods for your repository. Am I wrong to assume that the standardization of access to data is an integral piece of this pattern ? Rhino has a good article on implementation 1, and of course MS has a vague definition and an example of implementation 2 is here.

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  • Versioning Strategy for Service Interfaces JAR

    - by Colin Morelli
    I'm building a service oriented architecture composed (mostly) of Java-based services, each of which is a Maven project (in an individual repository) with two submodules: common, and server. The common module contains the service's interfaces that clients can include in their project to make service calls. The server submodule contains the code that actually powers the service. I'm now trying to figure out an appropriate versioning strategy for the interfaces, such that each interface change results in a new common jar, but changes to the server (so long as they don't impact the contract of the interfaces) receive the same common jar. I know this is pretty simple to do manually (simply increment the server version and don't touch the common one), but this project will be built and deployed by a CI server, and I'd like to come up with a strategy for automatically versioning these. The only thing I have been able to come up with so far is to have the CI server md5 the service interfaces.

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