如何：运行 java jar 的 Docker 容器连接到主机 mysql 服务器？

Question

I wrote a simple java program that should connect to the host machine running a MYSQL server and insert a record. The java progam is running inside a docker container with an ubuntu base image. At this point I have the jar working but can't connect to the host machine MYSQL server yet.

I've tried different mysql server installs and coppied from other dockerfiles in the hope to copy/past something together that works but it's getting messy and I don't know what parts are necessary anymore.

Java code:

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

class ConnectionTest {

    private Connection conn;

    ConnectionTest() throws IOException, ClassNotFoundException {
        try {
            test();
        } catch (SQLException e) {
            logError(e);
        }
    }

    private void logError(SQLException e) throws IOException {
        StringWriter sw = new StringWriter();
        PrintWriter pw = new PrintWriter(sw);
        e.printStackTrace(pw);
        String sStackTrace = sw.toString();

        File fout = new File("logs.txt");
        FileOutputStream fos = new FileOutputStream(fout);

        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(fos));

        bw.write(sStackTrace);

        bw.close();
    }

    private void test() throws SQLException, ClassNotFoundException { ;
        String hostname = "localhost";
        String dbName = "test";
        String userName = "root";
        String password = "";

        Class.forName("com.mysql.cj.jdbc.Driver");
        conn = DriverManager.getConnection("jdbc:mysql://" + hostname + ":3306/" + dbName + "?useLegacyDatetimeCode=false&serverTimezone=Europe/Paris", userName, password);

        PreparedStatement prep = conn.prepareStatement("INSERT INTO test(Login, Password) values('test', 'test')");
        prep.execute();
    }
}

Dockerfile:

RUN mkdir -p /root/java
COPY jdk-8u221-linux-x64.tar.gz /
RUN tar -zxf jdk-8u221-linux-x64.tar.gz -C /root/java

RUN apt-get update
RUN update-alternatives --install /usr/bin/java java /root/java/jdk1.8.0_221/bin/java 100

ENV JAVA_HOME /root/java/jdk1.8.0_221/bin
RUN export JAVA_HOME

RUN apt-get update \
 && DEBIAN_FRONTEND=noninteractive apt-get install -y mysql-server \
 && sed -i "s/127.0.0.1/0.0.0.0/g" /etc/mysql/mysql.conf.d/mysqld.cnf \
 && mkdir /var/run/mysqld \
 && chown -R mysql:mysql /var/run/mysqld

VOLUME ["/var/lib/mysql"]

CMD ["mysqld_safe"]

EXPOSE 3306

COPY lib /root/test/lib
COPY entrypoint.sh /

ENTRYPOINT ["/entrypoint.sh"]

Entrypoint.sh:

chmod -R 777 /root/test

cd /root/test

java -cp "lib/*" -jar lib/DockerTest.jar

tail -f /dev/null

/root/test/lib contains both the mysql-connector-java.jar and the DockerTest.jar. If I run mysqld before the jar the server starts but the jar won't launch.

MYSQL status when the server is running:

$ winpty docker exec -it mysql_container service mysql status
 * /usr/bin/mysqladmin  Ver 8.42 Distrib 5.7.27, for Linux on x86_64
Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Server version          5.7.27-0ubuntu0.16.04.1
Protocol version        10
Connection              Localhost via UNIX socket
UNIX socket             /var/run/mysqld/mysqld.sock
Uptime:                 3 sec

Threads: 1  Questions: 4  Slow queries: 0  Opens: 105  Flush tables: 1  Open tables: 98  Queries per second avg: 1.333

Error when running just the jar:

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)
        at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64)
        at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:832)
        at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:456)
        at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:240)
        at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:207)
        at java.sql.DriverManager.getConnection(DriverManager.java:664)
        at java.sql.DriverManager.getConnection(DriverManager.java:247)
        at ConnectionTest.test(ConnectionTest.java:42)
        at ConnectionTest.<init>(ConnectionTest.java:13)
        at Main.main(Main.java:5)
Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure

Answer 1

如果你正在使用Spring，你可以设置spring.datasource.url在application.properties到使用host.docker.internal:3306如果MySQL是你的本地/主机上运行。

spring.datasource.url=jdbc:mysql://host.docker.internal:3306/<yourdatabase>