How can I have multiple instances of databases configured?

Question

I've already gone through the existing questions on this but still not satisfied to the core.

To add multiple database configuration, following is the info i got so far is -

1) Update config.yml file -

database1:
  driverClass: com.mysql.jdbc.Driver
  user: user1
  password: user!23
  url: jdbc:mysql://url.to.connect:3306/db1
  properties: charSet: UTF-8
  maxWaitForConnection: 1s
  validationQuery: "/* MyService Health Check */ SELECT 1"
  minSize: 8
  maxSize: 32
  checkConnectionWhileIdle: false
  checkConnectionHealthWhenIdleFor: 10s
  closeConnectionIfIdleFor: 1 minute

database2:
  driverClass: com.mysql.jdbc.Driver
  user: user2
  password: user!23
  url: jdbc:mysql://url.to.connect:3306/db2
  properties: charSet: UTF-8
  maxWaitForConnection: 1s
  validationQuery: "/* MyService Health Check */ SELECT 1"
  minSize: 8
  maxSize: 32
  checkConnectionWhileIdle: false
  checkConnectionHealthWhenIdleFor: 10s
  closeConnectionIfIdleFor: 1 minute

2) Add the changes to java configuration file.

public class DropWizardConfiguration extends Configuration{

    @Valid
    @NotNull
    @JsonProperty
    private DatabaseConfiguration database1 = new DatabaseConfiguration();

    @Valid
    @NotNull
    @JsonProperty
    private DatabaseConfiguration database2 = new DatabaseConfiguration();

    public DatabaseConfiguration getDatabaseConfiguration1()
    {       
        return database1;
        }

        public DatabaseConfiguration getDatabaseConfiguration2()
    {       
        return database2;
        }
}

3) In this step, I should be updating the DropWizard service to handle the respective database instance.

public class DropWizardService extends Service<DropWizardConfiguration>{
    private final HibernateBundle<DropWizardConfiguration> hibernate = new HibernateBundle<DropWizardConfiguration>(Game.class) {

        // @Override
        public DatabaseConfiguration getDatabaseConfiguration(DropWizardConfiguration configuration){
            return configuration.getDatabaseConfiguration();
        }
    };

    @Override
    public void initialize(Bootstrap<DropWizardConfiguration> bootstrap) {  
        bootstrap.addBundle(hibernate);
    }

    public void run() throws Exception{
        this.run(new String[]{"server", "./config.yml"});
    }

    @Override
    public void run(DropWizardConfiguration configuration, Environment environment) throws Exception {
        SessionFactory factory = hibernate.getSessionFactory();     
        environment.addResource(new MyResource(factory));   
    }   
}

But this is where I'm going into a blackbox, I am not sure what configuration to change or How to change!

Appreciate some inputs.

Answer 1

I recently had to do something similar and the way I did it was by using BeanDefinitionRegistryPostProcessor. I used jdbcTemplates but it should be transferable to hibernate sessions aswel. Doing it this was I was able to add any amount of databases and the beans would get created. then just add the beans in the context file.

What I did was in the config

@Valid
@NotNull
@JsonProperty("database")
private Collection<DataSourceConfig> databases;

public Collection<DataSourceConfig> getDatabase() {
    return databases;
}

This is my DataSourceConfig class

public class DataSourceConfig {

@JsonProperty
private String name;

@JsonProperty
private String driverClassName;

@JsonProperty
private String username;

@JsonProperty
private String password;

@JsonProperty
private String url;

public String getDriverClassName() {
    return driverClassName;
}

public void setDriverClassName(String driverClassName) {
    this.driverClassName = driverClassName;
}

public String getUsername() {
    return username;
}

public void setUsername(String username) {
    this.username = username;
}

public String getPassword() {
    return password;
}

public void setPassword(String password) {
    this.password = password;
}

public String getUrl() {
    return url;
}

public void setUrl(String url) {
    this.url = url;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}
}

This is the method from my class that implements BeanDefinitionPostProcessor

public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {

    /**
     * Builds JdbcTemplates for beans
     */
    Map<String,String> jdbcTemplateBeanNames = Maps.newHashMap();
    for (DataSourceConfig dsc : configuration.getDatabase()) {
        AbstractBeanDefinition jdbcTemplateDefinition = BeanDefinitionBuilder.rootBeanDefinition("org.springframework.jdbc.core.JdbcTemplate")
                .addPropertyValue("dataSource",
                        BeanDefinitionBuilder.genericBeanDefinition(DriverManagerDataSource.class)
                            .addPropertyValue("driverClassName", dsc.getDriverClassName())
                            .addPropertyValue("url", dsc.getUrl())
                            .addPropertyValue("username", dsc.getUsername())
                            .addPropertyValue("password", dsc.getPassword())
                            .getBeanDefinition()
                )
                .getBeanDefinition();
        String name = BeanDefinitionReaderUtils.registerWithGeneratedName(jdbcTemplateDefinition, registry);
        jdbcTemplateBeanNames.put(dsc.getName(), name);

    }