The Spring container is at the core of the Spring Framework. The container will create the objects, wire them together, configure them, and manage their complete life cycle from creation till destruction. The Spring container uses DI to manage the components that make up an application. These objects are called Spring Beans, which we will discuss in the next chapter.
The container gets its instructions on what objects to instantiate, configure, and assemble by reading the configuration metadata provided. The configuration metadata can be represented either by XML, Java annotations, or Java code. The following diagram represents a high-level view of how Spring works. The Spring IoC container makes use of Java POJO classes and configuration metadata to produce a fully configured and executable system or application.

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Spring provides the following two distinct types of containers.

Sr.No.

Container & Description

Spring BeanFactory Container

This is the simplest container providing the basic support for DI and is defined by the org.springframework.beans.factory.BeanFactory interface. The BeanFactory and related interfaces, such as BeanFactoryAware, InitializingBean, DisposableBean, are still present in Spring for the purpose of backward compatibility with a large number of third-party frameworks that integrate with Spring.

Spring ApplicationContext Container

This container adds more enterprise-specific functionality such as the ability to resolve textual messages from a properties file and the ability to publish application events to interested event listeners. This container is defined by the org.springframework.context.ApplicationContext interface.

The ApplicationContext container includes all functionality of the BeanFactorycontainer, so it is generally recommended over BeanFactory. BeanFactory can still be used for lightweight applications like mobile devices or applet-based applications where data volume and speed is significant.

Table of Contents

AOP with Spring Framework

One of the key components of Spring Framework is the Aspect oriented programming (AOP) framework. Aspect-Oriented Programming entails breaking down program logic into distinct parts called so-called concerns. The functions that span multiple points of an application are called cross-cutting concerns and these cross-cutting concerns are conceptually separate from the application’s business logic. There are various common good examples of aspects like logging, auditing, declarative transactions, security, caching, etc.
The key unit of modularity in OOP is the class, whereas in AOP the unit of modularity is the aspect. Dependency Injection helps you decouple your application objects from each other and AOP helps you decouple cross-cutting concerns from the objects that they affect. AOP is like triggers in programming languages such as Perl, .NET, Java, and others.
Spring AOP module provides interceptors to intercept an application. For example, when a method is executed, you can add extra functionality before or after the method execution.

AOP Terminologies

Before we start working with AOP, let us become familiar with the AOP concepts and terminology. These terms are not specific to Spring, rather they are related to AOP.

Sr.No	Terms & Description
1	Aspect This is a module which has a set of APIs providing cross-cutting requirements. For example, a logging module would be called AOP aspect for logging. An application can have any number of aspects depending on the requirement.
2	Join point This represents a point in your application where you can plug-in the AOP aspect. You can also say, it is the actual place in the application where an action will be taken using Spring AOP framework.
3	Advice This is the actual action to be taken either before or after the method execution. This is an actual piece of code that is invoked during the program execution by Spring AOP framework.
4	Pointcut This is a set of one or more join points where an advice should be executed. You can specify pointcuts using expressions or patterns as we will see in our AOP examples.
5	Introduction An introduction allows you to add new methods or attributes to the existing classes.
6	Target object The object being advised by one or more aspects. This object will always be a proxied object, also referred to as the advised object.
7	Weaving Weaving is the process of linking aspects with other application types or objects to create an advised object. This can be done at compile time, load time, or at runtime.

Types of Advice

Spring aspects can work with five kinds of advice mentioned as follows −

Sr.No	Advice & Description
1	before Run advice before the a method execution.
2	after Run advice after the method execution, regardless of its outcome.
3	after-returning Run advice after a method execution only if method completes successfully.
4	after-throwing Run advice after a method execution only if method exits by throwing an exception.
5	around Run advice before and after the advised method is invoked.

Custom Aspects Implementation

Spring supports the @AspectJ annotation style approach and the schema-based approach to implement custom aspects. These two approaches have been explained in detail in the following sections.

Sr.No

Approach & Description

XML Schema based

Aspects are implemented using the regular classes along with XML based configuration.

@AspectJ based

@AspectJ refers to a style of declaring aspects as regular Java classes annotated with Java 5 annotations.

Spring – JDBC Framework Overview

While working with the database using plain old JDBC, it becomes cumbersome to write unnecessary code to handle exceptions, opening and closing database connections, etc. However, Spring JDBC Framework takes care of all the low-level details starting from opening the connection, prepare and execute the SQL statement, process exceptions, handle transactions and finally close the connection.
So what you have to do is just define the connection parameters and specify the SQL statement to be executed and do the required work for each iteration while fetching data from the database.
Spring JDBC provides several approaches and correspondingly different classes to interface with the database. I’m going to take classic and the most popular approach which makes use of JdbcTemplate class of the framework. This is the central framework class that manages all the database communication and exception handling.

JdbcTemplate Class

The JDBC Template class executes SQL queries, updates statements, stores procedure calls, performs iteration over ResultSets, and extracts returned parameter values. It also catches JDBC exceptions and translates them to the generic, more informative, exception hierarchy defined in the org.springframework.dao package.
Instances of the JdbcTemplate class are threadsafe once configured. So you can configure a single instance of a JdbcTemplate and then safely inject this shared reference into multiple DAOs.
A common practice when using the JDBC Template class is to configure a DataSource in your Spring configuration file, and then dependency-inject that shared DataSource bean into your DAO classes, and the JdbcTemplate is created in the setter for the DataSource.

Configuring Data Source

Let us create a database table Student in our database TEST. We assume you are working with MySQL database, if you work with any other database then you can change your DDL and SQL queries accordingly.

CREATE TABLE Student(
ID INT NOT NULL AUTO_INCREMENT,
NAME VARCHAR(20) NOT NULL,
AGE INT NOT NULL,
PRIMARY KEY (ID)
);

Now we need to supply a DataSource to the JDBC Template so it can configure itself to get database access. You can configure the DataSource in the XML file with a piece of code as shown in the following code snippet −

<bean id = "dataSource" 
class = "org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name = "driverClassName" value = "com.mysql.jdbc.Driver"/>
<property name = "url" value = "jdbc:mysql://localhost:3306/TEST"/>
<property name = "username" value = "root"/>
<property name = "password" value = "password"/>
</bean>

Data Access Object (DAO)

DAO stands for Data Access Object, which is commonly used for database interaction. DAOs exist to provide a means to read and write data to the database and they should expose this functionality through an interface by which the rest of the application will access them.
The DAO support in Spring makes it easy to work with data access technologies like JDBC, Hibernate, JPA, or JDO in a consistent way.

Executing SQL statements

Let us see how we can perform CRUD (Create, Read, Update and Delete) operation on database tables using SQL and JDBC Template object.

Querying for an integer

String SQL = “select count(*) from Student”;
int rowCount = jdbcTemplateObject.queryForInt( SQL );

Querying for a long

String SQL = “select count(*) from Student”;
long rowCount = jdbcTemplateObject.queryForLong( SQL );

A simple query using a bind variable

String SQL = “select age from Student where id = ?”;
int age = jdbcTemplateObject.queryForInt(SQL, new Object[]{10});

Querying for a String

String SQL = “select name from Student where id = ?”;
String name = jdbcTemplateObject.queryForObject(SQL, new Object[]{10}, String.class);

Querying and returning an object

String SQL = “select * from Student where id = ?”;
Student student = jdbcTemplateObject.queryForObject(
SQL, new Object[]{10}, new StudentMapper());

public class StudentMapper implements RowMapper<Student> {
public Student mapRow(ResultSet rs, int rowNum) throws SQLException {
Student student = new Student();
student.setID(rs.getInt("id"));
student.setName(rs.getString("name"));
student.setAge(rs.getInt("age"));

return student;
}
}

Querying and returning multiple objects

String SQL = “select * from Student”;
List<Student> students = jdbcTemplateObject.query(
SQL, new StudentMapper());

public class StudentMapper implements RowMapper<Student> {
public Student mapRow(ResultSet rs, int rowNum) throws SQLException {
Student student = new Student();
student.setID(rs.getInt("id"));
student.setName(rs.getString("name"));
student.setAge(rs.getInt("age"));

return student;
}
}

Inserting a row into the table

String SQL = “insert into Student (name, age) values (?, ?)”;
jdbcTemplateObject.update( SQL, new Object[]{“Zara”, 11} );

Updating a row into the table

String SQL = “update Student set name = ? where id = ?”;
jdbcTemplateObject.update( SQL, new Object[]{“Zara”, 10} );

Deleting a row from the table

String SQL = “delete Student where id = ?”;
jdbcTemplateObject.update( SQL, new Object[]{20} );

Executing DDL Statements

You can use the execute(..) method from jdbcTemplate to execute any SQL statements or DDL statements. Following is an example to use

CREATE statement to create a table −

String SQL = "CREATE TABLE Student( " +
"ID INT NOT NULL AUTO_INCREMENT, " +
"NAME VARCHAR(20) NOT NULL, " +
"AGE INT NOT NULL, " +
"PRIMARY KEY (ID));"

jdbcTemplateObject.execute( SQL );

Spring JDBC Framework Examples

Based on the above concepts, let us check few important examples which will help you in understanding usage of JDBC framework in Spring −

Sr.No.

Example & Description

Spring JDBC Example

This example will explain how to write a simple JDBC-based Spring application.

SQL Stored Procedure in Spring

Learn how to call SQL stored procedure while using JDBC in Spring.

So, this brings us to the end of blog. This Tecklearn ‘IoC Containers, AOP and JDBC Framework in Spring’ blog helps you with commonly asked questions if you are looking out for a job in Java Programming. If you wish to learn Spring and build a career Java Programming domain, then check out our interactive, Java and JEE Training, that comes with 24*7 support to guide you throughout your learning period. Please find the link for course details:

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• Installation of Java
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• Data types, Operations, Compilation process, Class files, Loops, Conditions
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• Object Oriented Programming in Java
• Implement classes and objects in Java
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• Overload Constructors
• Inheritance
• Inherit Classes and create sub-classes
• Implement abstract classes and methods
• Use static keyword
• Implement Interfaces and use it

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• String Handling –String Class
• Java Packages

Exception Handling and Multi-Threading

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• Introduction to multi-threading in Java
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Java Collections

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Java Database Connectivity (JDBC)

• Introduction to SQL: Connect, Insert, Update, Delete, Select
• Introduction to JDBC and Architecture of JDBC
• Insert/Update/Delete/Select Operations using JDBC
• Batch Processing Transaction
• Management: Commit and Rollback

Java Enterprise Edition – Servlets

• Introduction to J2EE
• Client Server architecture
• URL, Port Number, Request, Response
• Need for servlets
• Servlet fundamentals
• Setting up a web project in Eclipse
• Configuring and running the web app with servlets
• GET and POST request in web application with demo
• Servlet lifecycle
• Servlets Continued
• Session tracking and filter
• Forward and include Servlet request dispatchers

Java Server Pages (JSP)

• Fundamentals of Java Server Page
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• Introduction to JavaBeans
• ServletConfig and ServletContext
• Servlet Chaining
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Hibernate

• Introduction to Hibernate
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• Hibernate features
• Setting up a project with Hibernate framework
• Basic APIs needed to do CRUD operations with Hibernate
• Hibernate Architecture

POJO (Plain Old Java Object)

• POJO (Plain Old Java Object)
• Persistent Objects
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Spring

• Introduction to Spring
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Got a question for us? Please mention it in the comments section and we will get back to you.

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