Introducing Spring Framework

Chapter 3 ■ Applying Different Configurations
But wait! Bean? What does “bean” mean? In the Java world, this is a concept that has being around since the
Java language was created, so the Spring Framework team followed the same naming convention. A Java bean must
have some conventions like method naming (set/get/is), construction, and behavior, so it can be reusable and it
can interact with other beans and other classes. Later, in the Java community, the Java bean was transformed to the
well-known POJO: Plain Old Java Object.
The Spring Framework takes advantage of these conventions to know, create, inject, interact, and even destroy all
the declared classes on its container.
A bean is declared as a tag in the XML file and can contain the attributes described in Table 3-1.
Table 3-1. Bean Tag Attributes
Attribute
id
class
scope
init-method
factory-method
destroy-method
lazy-init
Description
An identifier for the bean. Only one unique ID can be defined.
Points to a concrete class, given the full java package.
Tells the Spring container how it will create the bean; by default if this scope property is not
set, the bean will be a singleton instance. Other scopes are prototype (an instance is created
every time the bean is required), request (a single instance is created in each HTTP web
request), and session (a bean is created and lives during the HTTP session).
This is the name of the method that will be called after a bean is created. It’s useful when you
want to set a state after your object is created.
This is the name of the method that will be used to create the bean. In other words, you need
to provide the method that will create the instance of the object, and this method should have
parameters.
This is the name of the method that will be called after you dispose of the bean.
This can be set to true if you want the container to create your bean when it’s being called
or used by you (when you called the getBean method) or maybe later from another instance
class that requires your object.
The Spring Framework has different ways to add information about your classes and their dependencies, and
how they interact with each other. All of this will be covered throughout the book by adding some features to your
Spring application, My Documents.
Listing 3-2 shows your SearchEngine implementation from the previous chapter: MySearchEngine looks like a lot
of code, and there is a lot of data hard-coded that has been added to the class. So what happens if you need to add more
types or more methods? You need to edit and recompile it again and again with any new changes. Too much work!
Listing 3-2. MySearchEngine.java
package com.apress.isf.java.service;
import java.util.ArrayList;
import java.util.List;
import com.apress.isf.java.model.Document;
import com.apress.isf.java.model.Type;
import com.apress.isf.java.service.SearchEngine;
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