How to provide a parameter value for an autowired variable? - spring

Question

I want to autowire a variable :
package com.ambre.hib.dao;
public interface LangDAO {
public String _getText();
}
package com.ambre.hib.dao;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.env.Environment;
public class LangDAOImpl implements LangDAO {
#Autowired
private Environment env;
private String code;
public LangDAOImpl() {
}
public LangDAOImpl(String code) {
this.code = code;
}
#Override
public String _getText() {
return env.getProperty(code);
}
}
package com.ambre.hib.config;
import javax.sql.DataSource;
import org.apache.commons.dbcp2.BasicDataSource;
import org.hibernate.SessionFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;
import org.springframework.orm.hibernate4.HibernateTransactionManager;
import org.springframework.orm.hibernate4.LocalSessionFactoryBuilder;
import org.springframework.transaction.annotation.EnableTransactionManagement;
import org.springframework.web.servlet.view.InternalResourceViewResolver;
import com.ambre.hib.dao.LangDAO;
import com.ambre.hib.dao.LangDAOImpl;
import com.ambre.hib.dao.UserDAO;
import com.ambre.hib.dao.UserDAOImpl;
import com.ambre.hib.model.User;
#Configuration
#ComponentScan("com.ambre.hib")
#EnableTransactionManagement
#PropertySource("classpath:lang.properties")
public class ApplicationContextConfig {
#Bean
public static PropertySourcesPlaceholderConfigurer properties() { // managing properties file ( languages )
return new PropertySourcesPlaceholderConfigurer();
}
#Bean(name = "viewResolver")
public InternalResourceViewResolver getViewResolver() {
InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
viewResolver.setPrefix("/WEB-INF/views/");
viewResolver.setSuffix(".jsp");
return viewResolver;
}
#Bean(name = "dataSource")
public DataSource getDataSource() {
BasicDataSource dataSource = new BasicDataSource();
dataSource.setDriverClassName("oracle.jdbc.driver.OracleDriver");
dataSource.setUrl("jdbc:oracle:thin:#localhost:1521:xe");
dataSource.setUsername("system");
dataSource.setPassword("a");
return dataSource;
}
#Autowired
#Bean(name = "sessionFactory")
public SessionFactory getSessionFactory(DataSource dataSource) {
LocalSessionFactoryBuilder sessionBuilder = new LocalSessionFactoryBuilder(dataSource);
sessionBuilder.addAnnotatedClasses(User.class);
return sessionBuilder.buildSessionFactory();
}
#Autowired
#Bean(name = "transactionManager")
public HibernateTransactionManager getTransactionManager(SessionFactory sessionFactory) {
HibernateTransactionManager transactionManager = new HibernateTransactionManager(sessionFactory);
return transactionManager;
}
#Autowired
#Bean(name = "userDao")
public UserDAO getUserDao(SessionFactory sessionFactory) {
return new UserDAOImpl(sessionFactory);
}
#Autowired
#Bean(name = "langDAO")
public LangDAO getLangDAO(String code) {
return new LangDAOImpl(code);
}
}
package com.ambre.hib.controller;
... // imports
#Controller
public class HomeController {
#Autowired
private LangDAO langDAO; // how to set here the String "title.home" to the constructor ?
#RequestMapping("/")
public String handleRequest(Model model) throws Exception {
model.addAttribute("titre", langDAO._getText());
return "UserList";
}
}
As you can see I autowired the class LangDAO in the controller. But I want to pass a String as its constructor parameter. How to do that ?

Answer 1

Since I can see that you've already configured the PropertySourcesPlaceholderConfigurer then you can autowire the property from the config file directly to the constructor like so:
#Autowired
public LangDAOImpl(#Value("${you_property_key}") String code) {
this.code = code;
}
or directly on the property
#Value("${you_property_key}") String code
Alternatively, if you define a #PostConstruct method you can get the property from the environment and set it yourself manually.

Answer 2

Values can be autowired in several ways
Spring provides a feature for Autowiring of the system properties.
#Value("${pool.size}")
public String size;
Using spring application context for passing values
<bean id="textEditor" class="com.tutorialspoint.TextEditor">
<constructor-arg value="${property.from.file}"/>
</bean>
Properties will be loaded into memory using
<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations">
<value>classpath:service.properties</value>
</property>
</bean>
ref: http://www.tutorialspoint.com/spring/spring_autowiring_byconstructor.htm