Recently we used JdbcTemplate in one of our projects. I tend to use Hibernate which is an ORM, whenever we need to work with databases. But lets have a short comparison between different options a java developer has for working with databases.
1. Java Database Connectivity (JDBC)
At first we can focus on the most basic alternative which is Java Database Connectivity (JDBC). JDBC is a standard java API for accessing data between the Java Standard Edition and a wide range of databases.
In short we can say JDBC API tasks are:
make and handle connections to database
creating SQL statements
executing SQL statements in target database
viewing and modifying resulting records
In most cases JDBC programming is a pain for developers as they need to manage primary things such as connections with repeating some basic codes.
2. Hibernate (ORM)
Hibernate object relational mapping provides a framework for mapping an object-oriented domain model to a relational database. So developer can focus only on the domain model and deliver all database related concerns into Hibernate. For example you can define a POJO class and relate it into a database table, instantiate an object from your class and tell Hibernate to save that object into the database table.
That's great as Hibernate handles almost all JDBC tasks itself.
But what if you need to work with database schema.
3. JdbcTemplate vs Hibernate-and-JDBC
It would be necessary in some situations to work with schema directly. For example you need to read data from a table which don't know its structure. JDBC can be a pain and also Hibernate tries to hide database concepts and elements. So Spring introduces JdbcTemplate which uses JDBC internally and provides a more facilitated API.
By JdbcTemplate we achieve the power of JDBC but no need for write boiler plate code.
The Spring JdbcTemplate has following advantages over standard JDBC:
JdbcTemplate has mechanism to clean-up resources automatically i.e. releasing the database connections
JdbcTemplate converts Jdbc SQLExceptions into RuntimeExceptions which allows the programmer to react more flexible to the errors
JdbcTemplate converts the vendor specific error messages into more understandable and unified set of error messages
JdbcTemplate provides methods to write the SQL queries directly
Spring is an open-source Framework who simplifies development complexities of java-based enterprise applications.
It provides infrastructural support at application level so that developers can focus only on business logic.
2. Framework of frameworks
Also Spring can be thought as a framework for frameworks" because Spring supports and facilitate using a wide range of frameworks such as Hibernate, Struts, etc.
3. Spring Main Approach
Spring at its core, is a dependency injection container which is a pattern for developing decoupled applications.
For example if you want to has an object of class ClassA which implements interface MyInterface in class ClassB one option is to new it (ClassA a = new(ClassA);) in class ClassB. This way we would couple class B with implementation of MyInterface and loose the flexibility of managed switching implementation from ClassA into another one.
In the other hand Spring manage lifecycle(creation and destroy) of objects (beans) itself, and so developer needs only to work with POJOs and you do not need an EJB container such as an application server.
So what happens if somebody, say Spring, can wire these dependencies?
4. Spring Magic
Now it's time to understand how Spring simplifies development process. Spring introduces a descriptive and conventional way in which developer can determine how things must be wired together.
For better understanding below is an example for inject dependency using XML while using Spring:
OneToMany Relationship
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<bean id="myInterface"class="ClassA"/>
<bean class="ClassB">
<propertyname="myInterface"ref="myInterface"/>
</bean>
Or using JAVA simply in another way you can annotate a variable of ClassA in ClassB:
OneToMany Relationship
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@Autowired
privateMyInterface myInterface;
5. Spring Features
Spring provides many features such as MVC, Aspec-Oriented-Programming, Batch, Integration, etc. That their explanation is beyond the scope of this article.
This article aims to make a short but well understanding of Spring framework essence.
