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

Question

我编写了一个简单的 java 程序，它应该连接到运行 MYSQL 服务器的主机并插入一条记录。 java 程序在一个 docker 容器内运行，其中包含一个 ubuntu 基础镜像。 在这一点上，我有 jar 工作，但还不能连接到主机 MYSQL 服务器。

我尝试了不同的 mysql 服务器安装并从其他 dockerfiles 复制，希望将一些有效的东西复制/过去，但它变得混乱，我不知道需要哪些部分了。

爪哇代码：

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"]

入口点.sh：

chmod -R 777 /root/test

cd /root/test

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

tail -f /dev/null

/root/test/lib 包含 mysql-connector-java.jar 和 DockerTest.jar。 如果我在 jar 之前运行 mysqld 服务器启动但 jar 不会启动。

服务器运行时的MYSQL状态：

$ 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

仅运行 jar 时出错：

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>