How can I connect two different database(mongo and postgres) in springboot with JPA?

I solved it myself. configuration code should be modified like below:

package com.dbmigrater.DBMigrater.config;

import org.hibernate.dialect.PostgreSQL82Dialect;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.boot.orm.jpa.hibernate.SpringImplicitNamingStrategy;
import org.springframework.boot.orm.jpa.hibernate.SpringPhysicalNamingStrategy;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;

import javax.sql.DataSource;
import java.util.HashMap;
import java.util.Map;

@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(
        entityManagerFactoryRef = "migrationEntityManager",
        transactionManagerRef = "migrationTransactionManager",
        basePackages = "com.dbmigrater.DBMigrater.repository.migration"
)
public class MigrationDBConfig {
    @Bean
    @Primary
    @ConfigurationProperties("spring.datasource.migration")
    public DataSource migrationDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean
    @Primary
    public PlatformTransactionManager migrationTransactionManager() {
        JpaTransactionManager transactionManager = new JpaTransactionManager();
        transactionManager.setEntityManagerFactory(migrationEntityManager().getObject());

        return transactionManager;
    }

    @Bean
    @Primary
    public LocalContainerEntityManagerFactoryBean migrationEntityManager() {
        LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
        em.setDataSource(migrationDataSource());
        em.setPackagesToScan("com.dbmigrater.DBMigrater.entity.migration");

        HibernateJpaVendorAdapter adapter = new HibernateJpaVendorAdapter();
        em.setJpaVendorAdapter(adapter);

        Map<String, Object> properties = new HashMap<>();
        properties.put("hibernate.physical_naming_strategy", SpringPhysicalNamingStrategy.class.getName());
        properties.put("hibernate.implicit_naming_strategy", SpringImplicitNamingStrategy.class.getName());
        properties.put("hibernate.dialect", PostgreSQL82Dialect.class.getName());

        em.setJpaPropertyMap(properties);

        return em;
    }
}

point is inner parameter of @CongifurationProperties() should be matched with application.yml. In this case, I change my parameter by spring.datasource.migraiton.

and because of I face the next error for mongo driver, I change my application.yml like below

spring:
  datasource:
    legacy:
      driver-class-name: "mongodb.jdbc.MongoDriver"
      jdbcUrl: "jdbc:mongodb://localhost:27017"
      username: "root"
      password: "root"
      database: "fromdb"
    migration:
      jdbcUrl: "jdbc:postgresql://localhost:5432/postgres"
      username: "root"
      password: "root"

Also, mongodb.jdbc.MongoDriver is not a exist class, I face another error: java.lang.RuntimeException: Failed to load driver class mongodb.jdbc.MongoDriver in either of HikariConfig class loader or Thread context classloader

If I solve this secondary problem, I will leave the solutions