Passing Dynamic arguments using setter injection in Springs - spring

Question

Iam trying to pass dynamic argument values i.e username from request using spring ioc.But iam unable to seen username value in userdaoimp.
UserDAOImpl.java
public class UserDAOImpl implements UserDAO {
private DataSource dataSource;
private JdbcTemplate jdbctemplate;
private String username;
public void setUsername(String username) {
this.username = username;
}
public DataSource getDataSource() {
return dataSource;
}
public void setDataSource(DataSource dataSource) {
this.dataSource = dataSource;
this.jdbctemplate =new JdbcTemplate (dataSource);
}
public int getUserListSize() {
System.out.println("UserDAOImpl::getUserListSize()"+username);
int count=this.jdbctemplate.queryForInt("SELECT COUNT(*) FROM USER_INFO");
return count;
}
}
epis.dao.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
<bean id="userdao" class="com.epis.dao.UserDAO">
<property name="dataSource">
<ref local="dataSource" />
</property>
<property name="username"/>
</bean>
</beans>
UserService

Answer 1

In the XML you can assing properties only to the surrounding bean.
so
will not work, because UserService does not have a filed username and therefor the spring should not start.
You can write it in two different ways:
<bean id="userdao" class="com.epis.dao.UserDAO">
<property name="dataSource" ref="dataSource" />
<property name="username" value="aaa"/>
</bean>
<bean ... class="...UserService">
<property name="userdao" ref="userdao" />
<bean>
or
<bean ... class="...UserService">
<property name="userdao">
<bean class="com.epis.dao.UserDAO">
<property name="dataSource" ref="dataSource" />
<property name="username" value="aaa"/>
</bean>
</property>
<bean>
But you can not mix both styles for one property.
Form the comment
Actually my requirement is the username value is getting based on other business logic in UserService.This username will be forwarded into userdao constructor.How can I forward that value to userdao.
This is not possible or at least not without a lot of handwritten magic. The reason is simple: The objects descriped in the XML file are created when the application starts, and the values are set while starting.
But in general I think you can achieve your aim with some scoped beans. But I have highly doubt that scoped beans can be used for the database connection.
I highly recommend to ask a new question hat focus on the dynamic requirement with the explanation you gave in the comment of this answer. (but without the bugy xml example) )
#See Spring Reference Chapter 3.5 Bean scopes

Answer 2

If you make username a property of the UserDaoImpl then it not longer be thread-safe, i.e. what would happen if two calls come in at the same time? The second call will overwrite the setting of the username property possibly before the getUserListSize() has been called the first time. You'd have to create a new UserDao object for every single call, which is not very efficient.
The easiest way is to use a parameter for your methods:
So in UserDao:
public int getUserListSize(String username);
In UserDaoImpl:
public int getUserListSize(String username) {
logger.debug("UserDAOImpl::getUserListSize():"+username);
int count = this.jdbctemplate.queryForInt(
"SELECT COUNT(*) FROM USER_INFO WHERE USER_NAME = ?", username);
return count;
}
And in UserService:
public int getUserListSize() {
String username = someBusinessLogicObtainsUsername();
return this.userDao.getUserListSize(username);
}