What is the difference between the Strategy pattern and Polymorphism in Java? I’m confused that whatever is achieved via Strategy Pattern is basically possible by polymorphism. Correct me if I’m wrong in this regard. Please, also provide me example to eradicate my confusion. Answer For me, the lin…
Get Set value from Redis using RedisTemplate
I am able to retrieve values from Redis using Jedis: But when I am trying to use Spring’s RedisTemplate , I am not getting any data. My data is stored in Redis as a Set. Can someone please point out to me what am I missing? EDIT : My xml config for RedisTemplate. Answer In short You have to configure
Is it possible to run RMI server in tomcat?
I have two tomact instances, running on Tomcat 7 (call it tomcat 1, tomcat 2). I need to arrange distributed computation. The server tomcat 1 should invoke some method on tomcat 2’s VM. Is it even possible to do? I know that Tomcat is a servlet container. Does it support such things? Answer Yes, it is p…
Java: Inverse of a matrix using EJML not working as expected
Within a java project I’ve developed I need to calculate the inverse of a matrix. In order to align with other projects and other developers I’m using the Efficient Java Matrix Library (orj.ejml). For inverting the Matrix I’m using invert from org.ejml.ops.CommonOps, and I has worked fine un…
Java for embedded systems? [closed]
Closed. This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed 1 year ago. Improve this question I have recently learned some basic Java and was thinking of seeing if I can…
Error loading fcl file in servlet
I have Java Web application JSP/Servlet that works with jFuzzyLogic library which uses rules.fcl file which is located at WEB-INF/rules/rules.fcl. I m trying to load the rules.fcl file in a servlet file but when i try to execute the application web i got these errors : Someone help me plz with it! Thanks. Ans…
How to install man page for Maven on linux?
I am using linux(mint mate), and installed maven by download & unzip & config the environment, I could use the mvn command. I want to have man mvn, not just mvn -help, any tip? @Update: To make the question clear, there is no man page for mvn, because I install maven by unzip, so I want to install man…
How to map an immutable collection with JPA and Hibernate
I am using JPA 2.1 and Hibernate as a JPA implementation, and I want to load a relationship as an immutable collection. Let’s take an example of an Employer parent entity that has an employees child collection. What can be done to instruct JPA to load an immutable employees collection? Answer You can us…
org.postgresql.util.PSQLException: ERROR: relation “app_user” does not exist
I have an application that I’m using spring boot and postgres. I’m getting this error when I try to create a user. When I run this query on my database, I get the same error: But if I change that to: It works. How can I configure that on my spring boot app? dependencies in pom.xml: application.pro…
Not supported for DML operations with JPA update query
This has been asked once before but the solution did not solve the issue. I am creating a JUnit test: The query the above test is calling is: Error: Answer The @Modifying annotation must be placed on the updateMaterialInventory method, along to the @Query annotation, to let Spring-data know that the query is …