我可以使用 Spring Boot 在正在运行的应用程序上添加数据库连接吗？

Question

例如，我有一个表单，我将在其中放置数据库连接的用户、密码、端口等，并在提交时建立​​并保存与数据库的连接。通常这是在应用程序运行之前在 application.properties 中完成的，但我可以在应用程序的运行时添加它吗？我这是可能的，我该怎么做？

Answer 1

一种解决方案是创建一个 DatabaseConnection 实体，其中包含您提到的所有必要连接属性（加上一个 active: boolean 属性）。使用 Spring Data 为该实体创建存储库并创建上层组件。为您的客户提供控制器以在该实体上进行 CRUD。

DatabaseConnectionService 可以提供到其他组件的活动 JDBC 连接以进行查询/更新。

Answer 2

在我的一个项目中遇到过类似的情况，使用spring-jdbc编写代码和维护会很困难。您可以使用普通的jdbc使用连接参数来获取指定的连接对象。

package com;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.Timestamp;

import org.apache.commons.lang3.exception.ExceptionUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
import org.springframework.util.Assert;

@Component
public class DB2Connection {

private static final Logger logger = LoggerFactory.getLogger(DB2Connection.class); 

private static String DRIVER_NAME;

private static String VALID_QUERY;

@Value("${db.valid-query}")
public void setValidQuery(String query){
    VALID_QUERY = query;
}

@Value("${db.driverName}")
public void setDriverName(String driverName){
    DRIVER_NAME = driverName;
}

/**
 *  Getting the Database connection
 *  @param  url             url of the database
 *  @param  userName        username of the db
 *  @param  password        password of the db
 *  @return Connection      returns DB Connection object 
 * */
public static Connection getConnection(final String url, final String userName, final String password){

    logger.info("Getting DB Connection...");

    Assert.notNull(url, "Database URL can't be null");
    Assert.notNull(userName, "Database username can't be null");
    Assert.notNull(password, "Database password can't be null");

    Connection con = null;
    try{
        Class.forName(DRIVER_NAME);
        con = DriverManager.getConnection(url,userName,password);

        // testing for the valid connection
        if(testConnection(con)){
            logger.info("Valid DB Connection # Connection Tested...");
        }else{
            logger.info("In-Valid DB Connection...");
        }
    }catch(ClassNotFoundException cla){
        logger.error("Class Not found exception..."+ExceptionUtils.getStackTrace(cla));
    }catch(SQLException sqe){
        logger.error("SQL Exception..."+ExceptionUtils.getStackTrace(sqe));
    }catch(Exception exe){
        logger.error("Exception occured while making DB Connection..."+ExceptionUtils.getStackTrace(exe));
    }
    return con;
}


/**
 *  Closing the java.sql.Connection class object 
 *  
 *  @param  con     Connection object which need to be closed
 *  
 * */
public static void close(Connection con){

    logger.info("Closing the connection object...");
    try {
        if(con != null ){
            con.close();
        }
    } catch (SQLException e) {
        logger.error("Exception occured while closing DBConnection..."+ExceptionUtils.getStackTrace(e));
    }
}

/**
 * This method will test connection if proper or not
 * @param   con     Connection object which need to be checked
 * @return  flag    true if connection is fine, false in case of connection is wrong
 * */
public static synchronized boolean testConnection(Connection con){

    boolean flag = false;
    logger.info("Testing the connection before providing to another process...");
    ResultSet rs = null;
    Statement stmt = null;
    try{
        stmt= con.createStatement();

        // running the query for validation of the database
        rs = stmt.executeQuery(VALID_QUERY);
        while(rs.next()){
            // if we get Timestamp as return type - valid query is successfully run in the database
            Timestamp t = rs.getTimestamp(1);
            if( t != null){
                flag =true;
            }
        }
    }catch(SQLException e){
        logger.error("SQL Exception error..."+ExceptionUtils.getStackTrace(e));
    }finally{
        if(rs != null){
            try {
                rs.close();
            } catch (SQLException e) {
                logger.error("Error in closing Result Set"+ExceptionUtils.getStackTrace(e));
            }
        }if( stmt != null){
            try {
                stmt.close();
            } catch (SQLException e) {
                logger.error("Error in closing Statement"+ExceptionUtils.getStackTrace(e));
            }
        }
    }
    return flag;
}

}

在 application.properties 文件中定义 db.valid-query 和 db.driverName 的值。 调用 getConnection() 获取连接对象。

您还可以创建自己的自定义执行器，它可以向您显示当前在应用程序中存在的所有当前连接对象。维护当前对象 DB Connection 对象所需的额外代码。