Spring-boot JDBC with multiple DataSources sample

Spring-Boot's auto-configurer seems good for simple applications. For example it automatically creates DataSource and JdbcTemplate, when you need to connect to the database. But what about less trivial configuration, when you have several different databases? I found the way to have multiple DataSources for Spring-Boot-based application. In the sample below I have two special (db-related) Configurations, one properties file with connections' parameters and two Repositories. Each @Repository connects with appropriate database through separate DataSource.

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

package sb; 
 
import org.springframework.boot.autoconfigure.jdbc.TomcatDataSourceConfiguration; 
import org.springframework.boot.context.properties.ConfigurationProperties; 
import org.springframework.context.annotation.Bean; 
import org.springframework.context.annotation.Configuration; 
import org.springframework.jdbc.core.JdbcTemplate; 
 
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

package sb; 
 
import org.springframework.boot.autoconfigure.jdbc.TomcatDataSourceConfiguration; 
import org.springframework.boot.context.properties.ConfigurationProperties; 
import org.springframework.context.annotation.Bean; 
import org.springframework.context.annotation.Configuration; 
import org.springframework.jdbc.core.JdbcTemplate; 
 
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

package sb; 
 
import org.slf4j.Logger; 
import org.slf4j.LoggerFactory; 
import org.springframework.beans.factory.annotation.Autowired; 
import org.springframework.beans.factory.annotation.Qualifier; 
import org.springframework.jdbc.core.JdbcTemplate; 
import org.springframework.jdbc.core.RowMapper; 
import org.springframework.stereotype.Repository; 
 
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

package sb; 
 
import org.slf4j.Logger; 
import org.slf4j.LoggerFactory; 
import org.springframework.beans.factory.annotation.Autowired; 
import org.springframework.beans.factory.annotation.Qualifier; 
import org.springframework.jdbc.core.JdbcTemplate; 
import org.springframework.jdbc.core.RowMapper; 
import org.springframework.stereotype.Repository; 
 
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; 
        } 
    }; 
} 

Controller.java

package sb; 
 
import org.slf4j.Logger; 
import org.slf4j.LoggerFactory; 
import org.springframework.beans.factory.annotation.Autowired; 
import org.springframework.web.bind.annotation.RequestMapping; 
import org.springframework.web.bind.annotation.RequestParam; 
import org.springframework.web.bind.annotation.RestController; 
 
@RestController 
public class Controller { 
    protected final Logger log = LoggerFactory.getLogger(getClass()); 
 
    @Autowired 
    private UserRepository users; 
 
    @Autowired 
    private ItemRepository items; 
 
    @RequestMapping("test") 
    public String test() { 
        log.info("Test"); 
        return "OK"; 
    } 
 
    @RequestMapping("user") 
    public User getUser(@RequestParam("id") long id) { 
        log.info("Get user"); 
        return users.getUser(id); 
    } 
 
    @RequestMapping("item") 
    public Item getItem(@RequestParam("id") long id) { 
        log.info("Get item"); 
        return items.getItem(id); 
    } 
 
} 

Application.java

package sb; 
 
import org.springframework.boot.SpringApplication; 
import org.springframework.boot.autoconfigure.EnableAutoConfiguration; 
import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration; 
import org.springframework.context.annotation.ComponentScan; 
import org.springframework.context.annotation.Configuration; 
 
@EnableAutoConfiguration(exclude = DataSourceAutoConfiguration.class) 
@Configuration 
@ComponentScan(basePackages = "sb") 
public class Application { 
 
    public static void main(String[] args) throws Throwable { 
        SpringApplication app = new SpringApplication(Application.class); 
        app.run(); 
    } 
} 

Spring-boot JDBC sample

Simple Web+JDBC application.

With spring-boot you just do your business. Without overhead, without extra manipulations and configurations. In example below: UserRepository provides information about users from database via JdbcTemplate, plain SQL-queries and RowMapper. UserController makes them accessible via HTTP. In this example spring-boot automatically configures DataSource and JdbcTemplate according to application.properties file. Sample urls: http://localhost:8080/user/test http://localhost:8080/user/user?id=2 http://localhost:8080/user/users?ids=1,3,5,7 Sources are minimalistic:

Application.java

package sb; 
 
import org.springframework.boot.SpringApplication; 
import org.springframework.boot.autoconfigure.EnableAutoConfiguration; 
import org.springframework.context.annotation.ComponentScan; 
import org.springframework.context.annotation.Configuration; 
 
@EnableAutoConfiguration 
@Configuration 
@ComponentScan 
public class Application { 
 
    public static void main(String[] args) throws Throwable { 
        SpringApplication app = new SpringApplication(Application.class); 
        app.setShowBanner(false); 
        app.run(args); 
    } 
} 

User.java

package sb;

public class User {
    public long id;
    public String name;
    public String alias;

    public User(long id, String name) {
        this.id = id;
        this.name = name;
    }
} 

UserController.java

package sb;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@RestController
@RequestMapping("user")
public class UserController {
    protected final Logger log = LoggerFactory.getLogger(getClass());

    @Autowired
    private UserRepository users;

    @RequestMapping("test")
    public String test() {
        log.info("Test");
        return "OK";
    }

    @RequestMapping("user")
    public User getUser(@RequestParam("id") long id) {
        log.info("Get user");
        return users.getUser(id);
    }

    @RequestMapping("users")
    public List<User> getUsers(@RequestParam("ids") long[] ids) {
        log.info("Get users");
        return users.getUsers(ids);
    }
} 

UserRepository.java

package sb;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;
import org.springframework.stereotype.Repository;
import org.springframework.util.ObjectUtils;
import org.springframework.util.StringUtils;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;

@Repository
public class UserRepository {
    protected final Logger log = LoggerFactory.getLogger(getClass());

    @Autowired
    protected JdbcTemplate jdbc;

    public User getUser(long id) {
        return jdbc.queryForObject("SELECT * FROM sb_user WHERE id=?", userMapper, id);
    }

    public List<User> getUsers(long[] ids) {
        String inIds = StringUtils.arrayToCommaDelimitedString(ObjectUtils.toObjectArray(ids));
        return jdbc.query("SELECT * FROM sb_user WHERE id IN (" + inIds + ")", userMapper);
    }

    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;
        }
    };

} 

application.properties

spring.datasource.driverClassName=org.postgresql.Driver
spring.datasource.url=jdbc:postgresql://srv0/test
spring.datasource.username=test
spring.datasource.password=test 

build.gradle

buildscript { 
    repositories { 
        maven { url "http://repo.spring.io/libs-snapshot" } 
    } 
    dependencies { 
        classpath("org.springframework.boot:spring-boot-gradle-plugin:0.5.0.M6") 
    } 
} 
 
apply plugin: "java" 
apply plugin: "spring-boot" 
 
buildDir = "out" 
 
jar { 
    baseName = "sb-jdbc" 
    version = "0.1" 
} 
 
repositories { 
    mavenCentral() 
    maven { url "http://repo.spring.io/libs-snapshot" } 
} 
 
dependencies { 
    def springBootVersion = '0.5.0.M6' 
 
    compile("org.springframework.boot:spring-boot-starter-web:$springBootVersion") 
    compile("org.springframework.boot:spring-boot-starter-jdbc:$springBootVersion") 
 
    compile("org.postgresql:postgresql:9.2-1003-jdbc4") 
} 

Spring-boot

Spring's guys are doing new revolutionary thing - spring-boot
With spring-boot creation of standalone application has become much easier and faster.
Auto-configurations, embedded servlet-containers, all-in-one jar - sometimes it looks like magic.
It seems OK for starters and prototypes, but what about production and hi-load applications...

Java -XX: AutoBoxCacheMax option

-XX:AutoBoxCacheMax=size option lets to control cache size for Integers.

In current Oracle HotSpot JVM (1.7) it only affects on Integer objects, created via autoboxing or Integer.valueOf(int i).

public class IntegersDemo {
    public static void main(String[] args) {
        {
            Integer a100 = 100;
            Integer b100 = 100;
            System.out.println(a100 == b100); //true
 
            Integer a200 = 200;
            Integer b200 = 200;
            System.out.println(a200 == b200); //false by default, 
            // but true when -XX:AutoBoxCacheMax=1000
        }
 
        {
            Integer a100 = Integer.valueOf(100);
            Integer b100 = Integer.valueOf(100);
            System.out.println(a100 == b100); //true
 
            Integer a200 = Integer.valueOf(200);
            Integer b200 = Integer.valueOf(200);
            System.out.println(a200 == b200); //false by default,
            // but true when -XX:AutoBoxCacheMax=1000
        }
 
        {
            Integer a100 = new Integer(100);
            Integer b100 = new Integer(100);
            System.out.println(a100 == b100); //always false, 
            // because of objects are allocated via "new"
        }
    }
}