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• performance of parameterized queries for different db's

  - by tuinstoel

  A lot of people know that it is important to use parameterized queries to prevent sql injection attacks. Parameterized queries are also much faster in sqlite and oracle when doing online transaction processing because the query optimizer doesn't have to reparse every parameterized sql statement before executing. I've seen sqlite becoming 3 times faster when you use parameterized queries, oracle can become 10 times faster when you use parameterized queries in some extreme cases with a lot of concurrency. How about other db's like mysql, ms sql, db2 and postgresql? Is there an equal difference in performance between parameterized queries and literal queries?

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• how to initialize spring bean from database

  - by wavelet

  hi,i use spring security and my config is in database: <sec:http auto-config="true" entry-point-ref="casProcessingFilterEntryPoint"> <sec:remember-me /> <sec:session-management> <sec:concurrency-control max-sessions="1" error-if-maximum-exceeded="true" /> </sec:session-management> <sec:logout logout-success-url="${host.url}/logout/" /> <sec:custom-filter ref="casAuthenticationFilter" after="CAS_FILTER" /> <sec:custom-filter ref="filterInvocationInterceptor" before="FILTER_SECURITY_INTERCEPTOR" /> </sec:http> like ${host.url} is in database how can i initialize ?

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• Advice about a good Java book?

  - by camac1

  Hi people, I am new to Java but have experience programming in C/C++/C#. I wanted to learn Java SE 6 first before moving to Java EE 6. After making some research online for appropriate Java SE 6 books, I found that these are appropriate for me to get an excellent idea of Java SE 6: 1) Head First Java, 2nd Edition 2) An Intermediate Level Book <----------- 3) Effective Java (2nd Edition) 4) Java Concurrency in Practice 5) Java Generics and Collections 6) Java Concise Reference Series: Swing And AWT 7) Java Reflection in Action However, I am having trouble choosing an Intermediate Level Book which will provide me with breadth and depth in Java SE 6. I was thinking about the book "Thinking in Java (4th Edition)"....Unfortunately, its deals with Java SE 5 and not the latest version. Could anybody please advice me an intermediate level book which could provide me with breadth and depth in Java SE 6. Regards

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• Injecting EntityManager Vs. EntityManagerFactory

  - by SB

  A long question, please bear with me. We are using Spring+JPA for a web application. My team is debating over injecting EntityManagerFactory in the GenericDAO(a DAO based on Generics something on the lines provided by APPFUSE, we do not use JpaDaosupport for some reason) over injecting an EntityManager. We are using "application managed persistence". The arguments against injecting a EntityManagerFactory is that its too heavy and so is not required, the EntityManager does what we need. Also, as Spring would create a new instance of a DAO for every web request(I doubt this) there are not going to be any concurrency issues as in the same EntityManager instance is shared by two threads. The argument for injecting EFM is that its a good practice over all its always good to have a handle to a factory. I am not sure which is the best approach, can someone please enlighten me? SB

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• Why hasn't functional programming taken over yet?

  - by pankrax

  I've read some texts about declarative/functional programming (languages), tried out Haskell as well as written one myself. From what I've seen, functional programming has several advantages over the classical imperative style: Stateless programs; No side effects Concurrency; Plays extremely nice with the rising multi-core technology Programs are usually shorter and in some cases easier to read Productivity goes up (example: Erlang) Imperative programming is a very old paradigm (as far as I know) and possibly not suitable for the 21st century Why are companies using or programs written in functional languages still so "rare"? Why, when looking at the advantages of functional programming, are we still using imperative programming languages? Maybe it was too early for it in 1990, but today?

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• What do you read?

  - by sixtyfootersdude

  I have almost finished reading all the articles on Joel on software. I am a new developer and hoping to get something interesting to read. Here is what is currently on my list: Java Concurrency in Practice by Brian Goetz sed & awk by Dougherty & Robbins (O'Reilly) The Pragmatic Programmer by Andrew Hunt and David Thomas Head First Design Patterns Can anyone suggest anything else? Would especially like something similar to Joel. Something that is a bit edgy but informative. Pragmatic programmer has some key concepts but is a bit dry.

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• Write a network simulator for fun

  - by Jono

  I want to write my own network simulator, for fun and for personal challenge. I hope to learn both new programming techniques, and a little bit more about networking. Previous object-oriented attempts ended very quickly, but I've recently downloaded and played with Microsoft's Axum (a new version was released today) and their Concurrency and Co-ordination Runtime. As I come from a very OO dominant background, I had never heard of Actor-oriented programming before; now it seems I've had my head in the sand until Scala and F# brought the paradigm to me. My questions are: a) is actor-oriented programming a better choice than object-oriented programming for this task, and if so b) where is a good place to start learning actor-oriented design?

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• Is it really wrong to version documents using CouchDB's behaviour?

  - by Tomas Sedovic

  This is one of those "I know I shouldn't do this but it's oh so convenient." questions. Sorry about that. I plan to use CouchDB for storing a bunch of documents and keeping their entire revision history. CouchDB does the versioning automatically, but it is strongly discouraged for programmer's use: "You cannot rely on document revisions for any other purpose than concurrency control." From what I've found on the CouchDB wiki, the versions can get deleted either during compaction or during replication. As far as I can tell, Compaction must always be triggered manually and Replication occurs only when there's more than one database server. The question is: if I won't run compaction and will use only single database instance for my documents, can I just use CouchDB's document versioning and expect it to work? What other problems I might run into? E.g. does not running compaction hurt the performance or consume significantly more disk space (than if I did handle the versioning manually)?

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• unable to catch org.hibernate.StaleObjectStateException while deleting record that doesn't exists in database

  - by JAB

  My application has a delete user option. Now in order to check concurrency condition I tried the following use case opened application in chrome and firefox browser. deleted user in firefox now trying to delete the same user in chrome browser I get exception org.hibernate.StaleObjectStateException .. which is right .. since I am trying to delete an object which doesn't exists. But I am not able to catch this exception try{ getHibernateTemplate().delete(userObj); } catch (StaleObjectStateException e) { e.printStackTrace(); } How do i catch this exception ??

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• What is the optimal number of threads for performing IO operations in java?

  - by marc

  In Goetz's "Java Concurrency in Practice", in a footnote on page 101, he writes "For computational problems like this that do not I/O and access no shared data, Ncpu or Ncpu+1 threads yield optimal throughput; more threads do not help, and may in fact degrade performance..." My question is, when performing I/O operations such as file writing, file reading, file deleting, etc, are there guidelines for the number of threads to use to achieve maximum performance? I understand this will be just a guide number, since disk speeds and a host of other factors play into this. Still, I'm wondering: can 20 threads write 1000 separate files to disk faster than 4 threads can on a 4-cpu machine?

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• Threading Problems in ActionScript 2.0?

  - by yar

  Is it possible to have concurrency problems (thread competition) in an onEnterFrame method in ActionScript 2.0? I have written this cheesy code as a guard: if (!busy) { // I suspect some threading problems: is that even possible in flash busy = true; movePanels(); busy = false; } but this is no assurance against thread competition. If so, how can I do a basic semaphore/lock? Note: I suspect threading problems in my app, but if they're impossible, I'll check my code differently.

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• Can we view objets in the JVM memory?

  - by Sebastien Lorber

  Hey, At work we found that on some instances (particulary the slow ones) we have a different behaviour, acquired at the reboot. We guess a cache is not initialized correctly, or maybe a concurrency problem... Anyway it's not reproductible in any other env than production. We actually don't have loggers to activate... it's an old component... Thus i'd like to know if there are tools that can help us to see the different objets present in the JVM memory in order to check the content of the cache... Thank you!

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• Emulating a transaction-safe SEQUENCE in MySQL

  - by Michael Pliskin

  We're using MySQL with InnoDB storage engine and transactions a lot, and we've run into a problem: we need a nice way to emulate Oracle's SEQUENCEs in MySQL. The requirements are: - concurrency support - transaction safety - max performance (meaning minimizing locks and deadlocks) We don't care if some of the values won't be used, i.e. gaps in sequence are ok. There is an easy way to archieve that by creating a separate InnoDB table with a counter, however this means it will take part in transaction and will introduce locks and waiting. I am thinking to try a MyISAM table with manual locks, any other ideas or best practices?

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• Arguments against Create or Update

  - by Nix

  Recently someone stated that they thought all Creates should be CreateOrUpdates. Instinctively i thought bad, but now I am trying to find out if I have any grounds. Situation interface IService{ void Create(Object a); void Update(Object a); } or interface IService{ void CreateOrUpdate(Object a); } My first thought is if you implemented everything CreateOrUpdate then you have no control if someone accidentally sends you wrong data, or concurrency issues where someone changes a "primary" field right before you call update.... But if you remove those cases, are there any other cons?

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• When is porting data from MySQL to CouchDB NOT advisable? Seeking cautionary tales

  - by dan

  I've dabbled in CouchDB and I have pretty good MySQL experience. I've also created one production application that uses both. I like MySQL but I've run into scaling/concurrency issues with MySQL that CouchDB advertises itself as a general solution for. The problem is that I have MySQL based applications that are pretty huge, and I don't really know whether it would be a good idea or not to try to port them over to a CouchDB datastore. I don't want to put in a lot of time and effort only to find out that my application is really not a good fit for CouchDB. Is there any sort of informed consensus on when porting a MySQL based app to CouchDB is NOT advisable? Any cautionary tales? I think CouchDB is really cool and want to use it more. I'd also like to know ahead of time what specific types of data querying scenarios CouchDB is really not good for, or if CouchDB can really replace MySQL for all the applications I create going forward.

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• Tips for measuring the parallelism speed-up in multi-core development.

  - by fnCzar

  I have read many of the good questions and answers around multi-core programming how-tos etc. I am familiar with concurrency, IPC, MPI etc but what I need is advice on how to measure speed-up which will help in making a business case of spending the time to write such code. Please don't answer with "well run it with single-core code then multi-core code and figure out the difference". This is neither a scientific nor a reliable way to measure performance improvement. If you know of tools that will do some of the heavy lifting please mention them. Answers pertaining to methodology will be more fitting but listing tools is ok as well.

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• Is MS Access still the most efficient RAD tool for small-scale custom apps?

  - by FastAl

  Of the many other development tools I've used, nothing holds a candle to the 'Functionality to Development Effort' ratio of MS Access. The reason I am asking is that I have been out of the language selection process for a few years, working on a large .Net system, and am only anecdotally familiar with the latest development tools outside the .Net world. I'm well aware of the limitations of Access, but for a limited concurrency (usually only 1 user at a time), small business, custom app, has anybody found a comparable end-to-end solution or combination that comes close? It doesn't have to be free, open source, or even Windows based. It just has to allow the same speed of development and maintenance, and maybe even provide some additional amenities like seamless autointegration with a server-based DB Engine (like Access does with its own 'Jet' dbms), better web support, and a file format more compatible with source control. I don't want to miss out on anything. Please share your development experience with your suggestions. Thanks.

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• Is Microsoft CCR gaining any traction?

  - by spender

  Microsoft's Concurrency and Coordination Runtime quite literally saved a project that was running into major issues with deadlocking. Since then I find that I use it more and more frequently for almost anything that requires asynchronous coding producing results that run lighter and faster than before. I can honestly state that it has transformed the way I think about multithread/multicore dev. Despite my personal love for CCR, there appears to be very little buzz surrounding it on the web and was wondering if anyone can offer any reason for this. Are there better alternatives, or is it a lack of promotion from MS, or are people simply happy with the existing tools?

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• How to create unique user key

  - by Grayson Mitchell

  Scenario: I have a fairly generic table (Data), that has an identity column. The data in this table is grouped (lets say by city). The users need an identifier in order for printing on paper forms, etc. The users can only access their cites data, so if they use the identity column for this purpose they will see odd numbers (e.g. a 'New York' user might see 1,37,2028... as the listed keys. Idealy they would see 1,2,3... (or something similar) The problem of course is concurrency, this being a web application you can't just have something like: UserId = Select Count(*)+1 from Data Where City='New York' Has anyone come up with any cunning ways around this problem?

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• How should flushing be handled in a doctrine EntityManager instance shared across different services in symfony2?

  - by Jbm

  I have defined several services in symfony 2 which persist changes to the database. These services have the doctrine instance as one of their dependencies: a.given.service: class: Acme\TestBundle\Service\AGivenService arguments: [@doctrine] If I have two different services and both of them persist objects through the EntityManager, which is obtained like this from the doctrine instance: $em = $doctrine->getEntityManager(); Would all services always share the same EntityManager? If so, how should I handle flushing if I wanted to handle all the changes in a single transaction? I have checked this: http://docs.doctrine-project.org/projects/doctrine-orm/en/2.0.x/reference/transactions-and-concurrency.html and it explains how to handle different transactions in a request, but I want to achieve the opposite, which is having different changes in different services handled as a single transaction. Is there a better approach to handle multiple changes in different services? For now my best bet is having a front-end service in charge of calling the other services and doing the flushing afterwards. Backend services would persist objects but would not do any flushing.

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• When is BIG, big enough for a database?

  - by David ???

  I'm developing a Java application that has performance at its core. I have a list of some 40,000 "final" objects, i.e., I have an initialization input data of 40,000 vectors. This data is unchanged throughout the program's run. I am always preforming lookups against a single ID property to retrieve the proper vectors. Currently I am using a HashMap over a sub-sample of a 1,000 vectors, but I'm not sure it will scale to production. When is BIG, actually big enough for a use of DB? One more thing, an SQLite DB is a viable option as no concurrency is involved, so I guess the "threshold" for db use, is perhaps lower.

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• Configuring jdbc-pool (tomcat 7)

  - by john

  i'm having some problems with tomcat 7 for configuring jdbc-pool : i`ve tried to follow this example: http://www.tomcatexpert.com/blog/2010/04/01/configuring-jdbc-pool-high-concurrency so i have: conf/server.xml <GlobalNamingResources> <Resource type="javax.sql.DataSource" name="jdbc/DB" factory="org.apache.tomcat.jdbc.pool.DataSourceFactory" driverClassName="com.mysql.jdbc.Driver" url="jdbc:mysql://localhost:3306/mydb" username="user" password="password" /> </GlobalNamingResources> conf/context.xml <Context> <ResourceLink type="javax.sql.DataSource" name="jdbc/LocalDB" global="jdbc/DB" /> <Context> and when i try to do this: Context initContext = new InitialContext(); Context envContext = (Context)initContext.lookup("java:/comp/env"); DataSource datasource = (DataSource)envContext.lookup("jdbc/LocalDB"); Connection con = datasource.getConnection(); i keep getting this error: javax.naming.NameNotFoundException: Name jdbc is not bound in this Context at org.apache.naming.NamingContext.lookup(NamingContext.java:803) at org.apache.naming.NamingContext.lookup(NamingContext.java:159) pls help tnx

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• Mysql with innodb and serializable transaction does not (always) lock rows

  - by Tobias G.

  Hello, I have a transaction with a SELECT and possible INSERT. For concurrency reasons, I added FOR UPDATE to the SELECT. To prevent phantom rows, I'm using the SERIALIZABLE transaction isolation level. This all works fine when there are any rows in the table, but not if the table is empty. When the table is empty, the SELECT FOR UPDATE does not do any (exclusive) locking and a concurrent thread/process can issue the same SELECT FOR UPDATE without being locked. CREATE TABLE t ( id INT NOT NULL AUTO_INCREMENT PRIMARY KEY, display_order INT ) ENGINE = InnoDB; SET TRANSACTION ISOLATION LEVEL SERIALIZABLE; START TRANSACTION; SELECT COALESCE(MAX(display_order), 0) + 1 from t FOR UPDATE; .. This concept works as expected with SQL Server, but not with MySQL. Any ideas on what I'm doing wrong? EDIT Adding an index on display_order does not change the behavior.

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• CFOs: Do You Have a Playbook for Growth?

  - by Oracle Accelerate for Midsize Companies

  by Jim Lein, Oracle Midsize Programs In most global markets, CFOs are optimistic about their company's growth opportunities. Deloitte's CFO Signals Report, "Time to Accelerate" found that: In the U.K. business optimism is at its highest level in three-and-a-half years Optimism in North America rose from a strong +42% last quarter (Q2 to Q3 2013) to an even stronger +54%. The inaugural Southeast Asia survey, 44% of CFOs reported a positive outlook despite worries over the Chinese economy and political uncertainty. Sustainable and profitable business growth doesn't usually happen by accident. Company's need a playbook for growth that's owned by the CFO. And today, that playbook must leverage the six enabling technologies--Social, Big Data, Mobile, Cloud, Analytics, and The Internet of Things (or, as Oracle president Mark Hurd explains, "The Internet of the People"). On Monday June 9 at  2:00 pm Eastern, CFO.com is hosting a webcast, "The CFO Playbook on Growth: How CFOs Can Boost Efficiency and Performance with Automation". Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} “Investing in technology begins with a business metric driven business case with clear tangible business results expected," says John Lieblang, Affiliate Partner with Waterstone Management Group. "The progressive CFO has learned how to forge a partnership with the CIO to align everyone in the 'result value chain' to be accountable for the business results not just for functional technology.” Click HERE to register  Looking for more news and information about Oracle Solutions for Midsize Companies? Read the latest Oracle for Midsize Companies Newsletter Sign-up to receive the latest communications from Oracle’s industry leaders and experts Jim Lein I evangelize Oracle's enterprise solutions for growing midsize companies. I recently celebrated 15 years with Oracle, having joined JD Edwards in 1999. I'm based in Evergreen, Colorado and love relating stories about creativity and innovation whether they be about software, live music, or the mountains. The views expressed here are my own, and not necessarily those of Oracle.

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• SQL query in JSP file pulling variable from VXML file

  - by s1066

  Hi I'm trying to get an SQL query to work within a JSP file. The JSP file is pulled by a VXML file here is my JSP file code: <?xml version="1.0"?> <%@ page import="java.util.*" %> <%@ page import="java.sql.*" %> <% boolean success = true; // Always optimistic String info = ""; String schoolname = request.getParameter("schoolname"); String informationtype = request.getParameter("informationtype"); try { Class.forName("org.postgresql.Driver"); String connectString = "jdbc:postgresql://localhost:5435/N0176359"; String user = "****"; String password = "*****"; Connection conn = DriverManager.getConnection(connectString, user, password); Statement st = conn.createStatement(); ResultSet rsvp = st.executeQuery("SELECT * FROM lincolnshire_school_information_new WHERE school_name=\'"+schoolname+"\'"); rsvp.next(); info = rsvp.getString(2); }catch (ClassNotFoundException e) { success = false; // something went wrong } %> As you can see I'm trying to insert the value of the variable declared as "schooname" into the end of the SQL query. However when I come to run the jsp file it doesn't work and I get an error "ResultSet not positioned properly". When I put a standard query in (without trying to make it value of the variable it works fine) Hope that makes sense, and thank you for any help!

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