spring connect to database based on availability of connections - spring

Question

In a application we are having three databaseserver
1. db1
2. db2
3.db3
we have configured jndi for the above connections
if no connection in db1 ,then from db2 the application will establish connection,if no connection in db2 the application will establish connection in db2.how to acheive this spring jdbc template. The details of server
tomcat 8.0 server,spring 4.0 ,oracle

Answer 1

This is an example to your question you can refer this source.
application.properties
spring.ds_items.driverClassName=org.postgresql.Driver
spring.ds_items.url=jdbc:postgresql://srv0/test
spring.ds_items.username=test0
spring.ds_items.password=test0
spring.ds_users.driverClassName=org.postgresql.Driver
spring.ds_users.url=jdbc:postgresql://srv1/test
spring.ds_users.username=test1
spring.ds_users.password=test1
DatabaseItemsConfig.java
import javax.sql.DataSource;
#Configuration
#ConfigurationProperties(name = "spring.ds_items")
public class DatabaseItemsConfig extends TomcatDataSourceConfiguration {
#Bean(name = "dsItems")
public DataSource dataSource() {
return super.dataSource();
}
#Bean(name = "jdbcItems")
public JdbcTemplate jdbcTemplate(DataSource dsItems) {
return new JdbcTemplate(dsItems);
}
}
DatabaseUsersConfig.java
import javax.sql.DataSource;
#Configuration
#ConfigurationProperties(name = "spring.ds_users")
public class DatabaseUsersConfig extends TomcatDataSourceConfiguration {
#Bean(name = "dsUsers")
public DataSource dataSource() {
return super.dataSource();
}
#Bean(name = "jdbcUsers")
public JdbcTemplate jdbcTemplate(DataSource dsUsers) {
return new JdbcTemplate(dsUsers);
}
}
ItemRepository.java
import java.sql.ResultSet;
import java.sql.SQLException;
#Repository
public class ItemRepository {
protected final Logger log = LoggerFactory.getLogger(getClass());
#Autowired
#Qualifier("jdbcItems")
protected JdbcTemplate jdbc;
public Item getItem(long id) {
return jdbc.queryForObject("SELECT * FROM sb_item WHERE id=?", itemMapper, id);
}
private static final RowMapper<Item> itemMapper = new RowMapper<Item>() {
public Item mapRow(ResultSet rs, int rowNum) throws SQLException {
Item item = new Item(rs.getLong("id"), rs.getString("title"));
item.price = rs.getDouble("id");
return item;
}
};
}
UserRepository.java
import java.sql.ResultSet;
import java.sql.SQLException;
#Repository
public class UserRepository {
protected final Logger log = LoggerFactory.getLogger(getClass());
#Autowired
#Qualifier("jdbcUsers")
protected JdbcTemplate jdbc;
public User getUser(long id) {
return jdbc.queryForObject("SELECT * FROM sb_user WHERE id=?", userMapper, id);
}
private static final RowMapper<User> userMapper = new RowMapper<User>() {
public User mapRow(ResultSet rs, int rowNum) throws SQLException {
User user = new User(rs.getLong("id"), rs.getString("name"));
user.alias = rs.getString("alias");
return user;
}
};
}