Docker + Spring Boot + Postgres-org.postgresql.util.PSQLException: The connection attempt failed

I have a Java Spring Boot app which works with a Postgres database. I want to use Docker for both of them. Initially, I created a docker-compose.yml file as given below:

version: '3.2'
services:
  postgres:
    restart: always
    container_name: sample_db
    image: postgres:10.4
    ports:
      - '5432:5432'
    environment:
         - POSTGRES_PASSWORD=root
         - POSTGRES_USER=root
         - POSTGRES_DB=test
# APP**
  web:
    build: .
    environment:
      SPRING_DATASOURCE_URL: jdbc:postgresql://db:5432/test
    expose:
      - 8080
    ports:
      - 8080:8080

Then,inside the application.properties file I defined the following properties.

server.port=8080
spring.jpa.generate-ddl=true
spring.datasource.url=jdbc:postgresql://db:5432/test
spring.datasource.driver-class-name=org.postgresql.Driver
spring.datasource.username=root
spring.datasource.password=root
spring.flyway.baseline-on-migrate=true
spring.flyway.enabled=false
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.PostgreSQLDialect
spring.jpa.hibernate.ddl-auto = none
spring.jpa.properties.hibernate.temp.use_jdbc_metadata_defaults: true

Also,I created a Dockerfile in my project directory, which looks like this:

FROM openjdk:8-jdk-alpine
VOLUME /tmp
EXPOSE 8080
RUN mkdir -p /app/
RUN mkdir -p /app/logs/
ADD target/household-0.0.1-SNAPSHOT.jar /app/app.jar
ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-Dspring.profiles.active=container", "-jar", "/app/app.jar"]

I issued these commands and ended up in the error as given below.

**mvn clean package
docker build ./ -t springbootapp  
docker-compose up**

The problem is the connection string. I believe I have to change it to something else, but I don't know what it should be. I get the following error messages:

web_1       | org.postgresql.util.PSQLException: The connection attempt failed.
web_1       |   at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:292) ~[postgresql-42.2.8.jar!/:42.2.8]
web_1       |   at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:49) ~[postgresql-42.2.8.jar!/:42.2.8]
web_1       |   at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:195) ~[postgresql-42.2.8.jar!/:42.2.8]
web_1       |   at org.postgresql.Driver.makeConnection(Driver.java:458) ~[postgresql-42.2.8.jar!/:42.2.8]
web_1       |   at org.postgresql.Driver.connect(Driver.java:260) ~[postgresql-42.2.8.jar!/:42.2.8]
web_1       |   at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:138) ~[HikariCP-3.4.2.jar!/:na]
web_1       |   at com.zaxxer.hikari.pool.PoolBase.newConnection(PoolBase.java:354) ~[HikariCP-3.4.2.jar!/:na]
web_1       |   at com.zaxxer.hikari.pool.PoolBase.newPoolEntry(PoolBase.java:202) ~[HikariCP-3.4.2.jar!/:na]
web_1       |   at com.zaxxer.hikari.pool.HikariPool.createPoolEntry(HikariPool.java:473) [HikariCP-3.4.2.jar!/:na]
web_1       |   at com.zaxxer.hikari.pool.HikariPool.checkFailFast(HikariPool.java:554) [HikariCP-3.4.2.jar!/:na]
web_1       |   at com.zaxxer.hikari.pool.HikariPool.<init>(HikariPool.java:115) [HikariCP-3.4.2.jar!/:na]
web_1       |   at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:112) [HikariCP-3.4.2.jar!/:na]
web_1       |   at org.hibernate.engine.jdbc.connections.internal.DatasourceConnectionProviderImpl.getConnection(DatasourceConnectionProviderImpl.java:122) [hibernate-core-5.4.12.Final.jar!/:5.4.12.Final]
web_1       |   at org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator$ConnectionProviderJdbcConnectionAccess.obtainConnection(JdbcEnvironmentInitiator.java:180) [hibernate-core-5.4.12.Final.jar!/:5.4.12.Final]
web_1       |   at org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator.initiateService(JdbcEnvironmentInitiator.java:68) [hibernate-core-5.4.12.Final.jar!/:5.4.12.Final]
web_1       |   at org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator.initiateService(JdbcEnvironmentInitiator.java:35) [hibernate-core-5.4.12.Final.jar!/:5.4.12.Final]
web_1       |   at org.hibernate.boot.registry.internal.StandardServiceRegistryImpl.initiateService(StandardServiceRegistryImpl.java:101) [hibernate-core-5.4.12.Final.jar!/:5.4.12.Final]
web_1       |   at org.hibernate.service.internal.AbstractServiceRegistryImpl.createService(AbstractServiceRegistryImpl.java:263) [hibernate-core-5.4.12.Final.jar!/:5.4.12.Final]
web_1       |   at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:237) [hibernate-core-5.4.12.Final.jar!/:5.4.12.Final]
web_1       |   at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:214) [hibernate-core-5.4.12.Final.jar!/:5.4.12.Final]
web_1       |   at org.hibernate.id.factory.internal.DefaultIdentifierGeneratorFactory.injectServices(DefaultIdentifierGeneratorFactory.java:152) [hibernate-core-5.4.12.Final.jar!/:5.4.12.Final]

The application works fine in local but facing issue while dockerizing it. Please let me know if any issues.