数据库无法连接 spring 启动

Question

I tried to build RestFull webservice with db connection. But this seems to not connecting with the database. And I get this error in my console.

   com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure

    The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
        at com.mysql.cj.jdbc.exceptions.SQLError.createCommunicationsException(SQLError.java:174) ~[mysql-connector-java-8.0.18.jar:8.0.18]
        at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64) ~[mysql-connector-java-8.0.18.jar:8.0.18]
        at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:836) ~[mysql-connector-java-8.0.18.jar:8.0.18]



The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_162]
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) ~[na:1.8.0_162]
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) ~[na:1.8.0_162]


Caused by: java.net.UnknownHostException: db_example
    at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method) ~[na:1.8.0_162]
    at java.net.InetAddress$2.lookupAllHostAddr(Unknown Source) ~[na:1.8.0_162]

Caused by: org.hibernate.service.spi.ServiceException: Unable to create requested service [org.hibernate.engine.jdbc.env.spi.JdbcEnvironment]
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.createService(AbstractServiceRegistryImpl.java:275) ~[hibernate-core-5.4.6.Final.jar:5.4.6.Final]
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:237) ~[hibernate-core-5.4.6.Final.jar:5.4.6.Final]

Caused by: org.hibernate.HibernateException: Access to DialectResolutionInfo cannot be null when 'hibernate.dialect' not set
    at org.hibernate.engine.jdbc.dialect.internal.DialectFactoryImpl.determineDialect(DialectFactoryImpl.java:100) ~[hibernate-core-5.4.6.Final.jar:5.4.6.Final]
    at org.hibernate.engine.jdbc.dialect.internal.DialectFactoryImpl.buildDialect(DialectFactoryImpl.java:54) ~[hibernate-core-5.4.6.Final.jar:5.4.6.Final]

This is my application.property file

server.port=8092

#spring.datasource.driverClassName=org.postgresql.Driver
spring.datasource.url=jdbc:mysql://db_example:3306/db_example
spring.datasource.username=root
spring.datasource.password=


#spring.jpa.database-platform=org.hibernate.dialect.PostgreSQLDialect
spring.jpa.show-sql=false
spring.jpa.hibernate.ddl-auto=create

I can't figure out what is the wrong with this.

Answer 1

    spring.datasource.url=jdbc:mysql://localhost:3306/db_example
    spring.datasource.username = root
    spring.datasource.password = root
    spring.jpa.properties.hibernate.dialect =org.hibernate.dialect.MySQL5Dialect

hibernate.dialect=org.hibernate.dialectMySQL5Dialect
hibernate.show_sql=true
hibernate.hbm2ddl.auto=create
hibernate.ddl-auto=validate

hibernate.connection.url=jdbc:mysql://localhost:3306/axa_india?useUnicode=true&characterEncoding=UTF-8&zeroDateTimeBehavior=convertToNull
hibernate.connection.username=root
hibernate.connection.password=root

Answer 2

I think the host name is something wrong here.So Kindly check once the host machine name like localhost (or) your proper DB hosted place name.

Because it is showing Exception like unknownHostException.

Answer 3

its duplicate ticket, check with: https:/stackoverflow.com/questions/2983248/com-mysql-jdbc-exceptions-jdbc4-communicationsexception-communications-link-fai