创建后端Java RESTful API，该API将与存储在云中的数据库进行通信

问题描述 投票：0回答：1

我目前正在学习Java EE，并被要求开发一个后端RESTful Java API，该API将与存储在云解决方案（IBM Bluemix）上的数据库进行通信。

我目前使用Eclipse Photon作为IDE，并且不是计算机的管理员用户。

我被要求使用IBM Was Liberty服务器插件测试我的代码以进行Eclipse，但是在设置服务器时遇到了一些麻烦。 我想我可能还不了解该插件的工作原理，也无法按照我的意愿使其工作。

问题是我无法通过我的api或管理中心访问存储在该服务器上的数据库（甚至无法登录管理中心）。

这是我使用（修改）并在此站点上找到的Java代码 

package connection;

//STEP 1. Import required packages
import java.sql.*;

public class FirstExample {
 // JDBC driver name and database URL
 static final String JDBC_DRIVER = "com.mysql.cj.jdbc.Driver";  
 static final String DB_URL = "jdbc:mysql://localhost:3306/ibm/api/validator/dataSource/SAMPLEDB";
 //  Database credentials
 static final String USER = "admin";
 static final String PASS = "admin";

 public static void main(String[] args) {
 Connection conn = null;
 Statement stmt = null;
 try{
    //STEP 2: Register JDBC driver
    Class.forName(JDBC_DRIVER);

    //STEP 3: Open a connection
    System.out.println("Connecting to database...");
    conn = DriverManager.getConnection(DB_URL, USER, PASS);

    //STEP 4: Execute a query
    System.out.println("Creating statement...");
    stmt = conn.createStatement();
    String sql;
    sql = "SELECT * FROM *";
    ResultSet rs = stmt.executeQuery(sql);

    //STEP 5: Extract data from result set
    while(rs.next()){
       //Retrieve by column name

       String data = rs.getString("last");
       //Display values
       System.out.println("Data Retreived " + data);
    }
    //STEP 6: Clean-up environment
    rs.close();
    stmt.close();
    conn.close();
 }catch(SQLException se){
    //Handle errors for JDBC
     System.out.println("\nJDBC ERROR ! \n");
    se.printStackTrace();
 }catch(Exception e){
    //Handle errors for Class.forName
     System.out.println("\nClass.forName ERROR ! \n");
    e.printStackTrace();
 }finally{
    //finally block used to close resources
    try{
       if(stmt!=null)
          stmt.close();
    }catch(SQLException se2){
        System.out.println("\nSQL ERROR ! NOTHING TO DO \n");
    }// nothing we can do
    try{
       if(conn!=null)
          conn.close();
    }catch(SQLException se){
        System.out.println("\nJDBC ERROR ! MAYBE SOMETHING TO DO \n");
       se.printStackTrace();
    }//end finally try
 }//end try
 System.out.println("\nGoodbye!");
}//end main
}//end FirstExample

至于我的Server.xml，这是更新的代码： 

<server description="Liberty beta">

    <featureManager>
        <feature>webProfile-8.0</feature>
        <feature>adminCenter-1.0</feature>
        <feature>restConnector-2.0</feature>
        <feature>transportSecurity-1.0</feature>
        <feature>logstashCollector-1.1</feature>
        <feature>validator-1.0</feature>

        <feature>mpConfig-1.3</feature>
        <feature>mpFaultTolerance-1.1</feature>
        <feature>mpHealth-1.0</feature>
        <feature>mpJwt-1.0</feature>
        <feature>mpMetrics-1.1</feature>
        <feature>mpOpenAPI-1.0</feature>
        <feature>mpOpenTracing-1.0</feature>
        <feature>mpRestClient-1.0</feature>

        <feature>localConnector-1.0</feature>
        <feature>jdbc-4.2</feature>
    </featureManager>

    <httpEndpoint   id="defaultHttpEndpoint"
                    host="*"
                    httpPort="9080"
                    httpsPort="9443" />

    <applicationManager autoExpand="true"/>

    <keyStore   id="defaultKeyStore"
                password="Liberty" />

    <basicRegistry id="userReg">
        <user   password="admin"
                name="admin"
                id="admin"></user>
    </basicRegistry>

    <administrator-role>
        <user>admin</user>
    </administrator-role>

    <remoteFileAccess>
        <writeDir>${server.config.dir}</writeDir>
    </remoteFileAccess>

    <dataSource id="DefaultDataSource" jndiName="jdbc/mySQL">
        <jdbcDriver libraryRef="MySQLLib" />
        <properties.microsoft.sqlserver databaseName="SAMPLEDB" serverName="localhost" portNumber="3306" user="admin" password="admin"/>
        <connectionManager></connectionManager>
    </dataSource>
    <library id="MySQLLib">
        <file name="C:/PUBLIC/tools/mysql-connector-java-8.0.12/mysql-connector-java-8.0.12/mysql-connector-java-8.0.12.jar" />
    </library>    

</server>

我现在遇到的问题是我似乎无法与服务器通信。

这是控制台错误： 

Connecting to database...

JDBC ERROR ! 


Goodbye!
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 connection.FirstExample.main(FirstExample.java:23)
Caused by: com.mysql.cj.exceptions.CJCommunicationsException: 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 sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61)
    at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105)
    at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151)
    at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167)
    at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:91)
    at com.mysql.cj.NativeSession.connect(NativeSession.java:152)
    at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:952)
    at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:822)
    ... 6 more
Caused by: java.net.ConnectException: Connection refused: connect
    at java.net.DualStackPlainSocketImpl.connect0(Native Method)
    at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79)
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
    at java.net.Socket.connect(Socket.java:589)
    at com.mysql.cj.protocol.StandardSocketFactory.connect(StandardSocketFactory.java:173)
    at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:65)
    ... 9 more
java mysql java-ee jdbc websphere-liberty
1个回答
0
投票

作为一个初学者，我试图盲目地遵循在线上找到的教程，并且对我实际上在做什么并不怎么想。

我不知道Was Liberty不喜欢使用所需的服务来设置VM，而且在Liberty中设置 dataSource并不是在设置数据库 。 缺乏信息，指导和严谨性，我认为在创建数据源时，Liberty服务器实际上正在运行mySQL服务器。 实际上（如果我错了，请纠正我）这部分代码， 

<dataSource id="DefaultDataSource" jndiName="jdbc/mySQL">
    <jdbcDriver libraryRef="MySQLLib" />
    <properties.microsoft.sqlserver databaseName="SAMPLEDB"
                                    serverName="localhost"
                                    portNumber="3306"
                                    user="admin"
                                    password="admin"/>
    <connectionManager></connectionManager>
</dataSource>

<library id="MySQLLib">
    <file name="C:/PUBLIC/tools/mysql-connector-java-8.0.12/mysql-connector-java-8.0.12/mysql-connector-java-8.0.12.jar" />
</library>

旨在使用足够的驱动程序在服务器中设置服务，以连接到远程数据库。 在这种情况下，我已经使用mySQL驱动程序设置了一个数据源。

当我确实运行本地mySQL服务器时，我能够通过我的Java应用程序进行通信和发送查询。

感谢那些花时间阅读这篇文章并尝试帮助我的人们。

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