Category Archives: I am Learning

Atomic Update MongoDB Java Example

In the previous post i.e Document Logical Querying MongoDB Java Example
Replacement in MongoDB
we have
seen how we were updating the
document – first by getting the
document using findOne() , then
updating its values and finally
putting it back in the collection.
We can also achieve the same task
in a single step i.e skipping findOne() invocation and by using atomic update modifiers provided by mongodb. This post will focus on update mongodb java example. Continue reading Atomic Update MongoDB Java Example

Logical Querying MongoDB Java Example

This post will focus on the logical Logical Querying MongoDB Java Example
operators that are available in
momgodb.I will use Java for the
illustration purpose of these
operators. You can use any of
the language for which mongo
driver is available. For the comparison operators you can refer the previous post here.
There are 4 logical operators that have been documented in mongodb specs.
We will continue with the same example that we have seen in the previous post. Continue reading Logical Querying MongoDB Java Example

Conditional Querying MongoDB Java Example

In the previous post we have seen  Conditional Querying MongoDB Java Example
different variations of find() method ,
but in real life we need much more than the exact matching  e.g we want to query  in ranges (using in ) , combine multiple conditions together (using OR , AND)  , using negation etc. In this post we will cover the comparison query operators that comes under the conditional querying in MongoDB :

Here, we will continue with the same example that we have used in the previous post , in Continue reading Conditional Querying MongoDB Java Example

Metaspace in Java8

Metaspace in Java8One of the new features that we will see in Java8 is the introduction of Metaspace. Metaspace is nothing but a replacement of our old friend PermGen (Permanent Generation) space.

What is PermGen?
The permanent Generation is part of your heap space that is actually used to store meta-data information for the classes created by users and prior to Java 7, it is also used to store interned Strings (interned strings – used to remove String duplicates by internalizing them to reduce memory consumption). As of Java 7, intern strings also moved as a part of heap space to make the more space available in Continue reading Metaspace in Java8

Querying MongoDB Java Example

In the earlier post Mongodb java Hello World Example we have seen some basic operations on the MongoDB and searching the document was one of them there we had used find().In this post we will more focus on querying mongdb with java using find() method that is basically used for querying documents in mongodb collections. We will see that how we can use find() in different ways to meet our query needs.Below are the 4 basic scenarios that we are going to cover under querying mongodb java example.

  1. Fetching all the documents from a collection.
  2. Fetching a subset of documents from a collection.
  3. Fetching only selected keys of a document from a collection.
  4. Exclude some keys of a document from a collection.

Querying MongoDB with Java

For this example the document that we are using will have structure something like this , it has Continue reading Querying MongoDB Java Example

Remove() Vs Drop() in MongoDB

Once we have documents stored in our collection , we can remove all of the documents from it in two ways. Now choosing one over other is totally depends on your requirement.

  • Using remove()
  • Using drop()

This post will show a comparison on Remove() Vs Drop() in MongoDB.

remove() vs drop() in mongodb

Before using one of them lets try to look into the pros and cons of each other.

  1. Using Remove():  remove has two overloaded versions ,one in which we will pass the Continue reading Remove() Vs Drop() in MongoDB

MongoDB Java Hello World Example

In the previous post  we have seen some of the basics on the primary keys and ObjectId in MongoDB.Now its time to get our hands dirty with some code , here I am using Java to interact with our mongo database. In this MongoDB Java Hello World example we will cover the following points : –

MongoDB Java Hello World Example
MongoDB Java Hello World Example
  1. Connect to mongodb server
  2. Connect to a database / Create a new Database
  3. Create a new collection
  4. Insert a new Document
  5. Search a Document
  6. Update a Document
  7. Delete a Document Continue reading MongoDB Java Hello World Example

_id and ObjectId in MongoDB

MongoDB has its own style of storing the  documents in the collection and providing the uniqueness to these documents is an important aspect of MongoDB.
So , it is very important that before we go into the higher end of Mongo we should understand what are _id and ObjectId in MongoDB.

_id and ObjectIds in MongoDB-1
MongoDB Official Logo

In relational databases like Oracle , DB2,MySQL etc whenever we insert any row into the database of our application we never care about providing the Continue reading _id and ObjectId in MongoDB

Default Methods in Java 8 Explained – Part 2 (A comic way)

If you have missed out the first part of this story i.e Default Methods in Java 8 ,you can read it here , else you can read the recap of first part here.

Recap : Interface IRoleService (i.e project manager) decided to assign extra duties to all (developer,tester ,ba etc) who are working on the project by introducing a new method extraDuties() in its interface. After this introduction of new extra duties  , TesterServiceImpl (i.e Tester of the application) rebelled and clear that he won’t perform any extra duties.When senior manager came to know about this situation , he advised interface IRoleService to introduce default methods so that no body will be forced to provide an implementation for extraDuties().

Now before going ahead let’s look at the code how default methods will be invoked and what Continue reading Default Methods in Java 8 Explained – Part 2 (A comic way)

Default Methods in Java 8 Explained – Part 1 (A comic way)

Default methods in Java 8 or we can also call them defender methods is one of the new feature that you will see in Java 8.  I would rather say it is one of the most awaited feature should have been introduced in the earlier versions itself.Anyways its never been late so that it can’t be used , I think finally its a great introduction by Oracle Java Team.

Now as we know in Java (prior to 8) all the implementation classes (non abstract) of an interface have to agree the interface contract and under that contract they have to provide the concrete implementations of all the methods available in interface that they are implementing , if you missed in providing implementation for even a single method ,compiler will start complaining about it.

Now consider a scenario you want to have a method in your interface and you don’t want to Continue reading Default Methods in Java 8 Explained – Part 1 (A comic way)

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