Single or multiple instances

[nilu chan]

I have written a spring web based application that has access to the database and I have the following class defined for accessing database.

MasterDao.java

/* The only DAO class for performing all DB CRUD operations of the application */
public final class MasterDao {
    
    static final Logger logger = Logger.getLogger(MasterDao.class);

    private JdbcTemplate jdbcTemplate;

    public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
        this.jdbcTemplate = jdbcTemplate;
    }

    public List getAllEmployees() {
        String sql = "select to_char(a.hire_date, 'mm/dd/yyyy') as hire_dt, a.*, b.*, c.*   from employees a, departments b, jobs c "
                + " where a.department_id = b.department_id  and a.job_id = c.job_id and a.enabled='Y' "
                + " order by a.last_name, a.first_name";
        return executeEmployeeQuery(sql);
    }

    //more code down here

I am using the following xml mapping for wiring the DAO class in my applicationContext.xml file
applicationContext.xml

    //code for accessing JNDI name here......    

    <bean id="masterDao" class="hrsampleapp.dao.MasterDao">
        <property name="jdbcTemplate"><ref bean="jdbcTemplate"/></property>
    </bean>

    <bean id="showAllProductsController" class="hrsampleapp.controller.ShowAllProductsController">
        <constructor-arg>
            <ref bean="masterDao"/>
        </constructor-arg>
    </bean>

    <bean id="addToCartController" class="hrsampleapp.controller.AddToCartController">
        <constructor-arg>
            <ref bean="masterDao"/>
        </constructor-arg>
    </bean>

I have the following questions related to my MasterDao class.
1) Will two instances of MasterDao class be created? One for showAllProductsController and one for addToCartController ?
2) Shouldn't all the methods defined in MasterDao class be static so that nobody can new an instance and call these methods ?

[Rishi Shehrawat]

Will two instances of MasterDao class be created? One for showAllProductsController and one for addToCartController ?

A single instance of MasterDAO will be created & injected in the controllers. The default scope for beans created by Spring is singleton.

Shouldn't all the methods defined in MasterDao class be static so that nobody can new an instance and call these methods ?

For beans created/manged by Spring the new construct is not supposed to be used. Spring creates the beans & manages the lifecycle of the beans, i:e manages dependency.