Scala JDBC操作数据库

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Scala 操作数据库（查询、插入、更新）

Scala操作数据库需要载入 java.sql.DriverManager ，我们分为查询和插入两个模块进行，每个模块也分为一条记录和多条记录来操作
首先，需要导入必须的信息，定义你要访问的JDBC地址和你的表名

import java.sql.DriverManager

import org.joda.time.DateTime

import scala.collection.mutable

object JDBCTest {

  // 你要访问的表名
  val cacheTable = "test_table" // table schema (create_time:bigint, key:text, result:text)
  // 你的JDBC地址，这里以postgre数据库为例
  val jdbcUrl = "jdbc:postgresql://ip:port/database_name?user=user_name&password=user_password"

  def main(args: Array[String]): Unit = {

  }

}

其中，joda模块是一个巨好用的时间模块，需要在pom文件中加入依赖

        <dependency>
            <groupId>joda-time</groupId>
            <artifactId>joda-time</artifactId>
            <version>2.9.2</version>
        </dependency>

joda时间模块非常友好，这是joda的官网地址 https://www.joda.org/joda-time/ ，因为本文中create_time需要用到时间戳，如果不想用joda，可以直接使用系统时间函数 System.currentTimeMillis() / 1000来写入时间戳。关于joda还有个比较完整的时间模块的封装，可以直接上手调用 Scala中时间处理org.joda.time.DateTime工具 ,下面开始正文

查询一条记录

/**
    * 查询一条记录,根据key查询一条记录
    *
    * @param key 查询Key
    * @return 没有记录-返回null，多条记录-返回最新的，一条记录-返回本条
    */
  def getResult(key: String): String = {
    val curJdbcUrl = jdbcUrl
    val resultList = new mutable.ArrayBuffer[(Long, String)]
    val conn = DriverManager.getConnection(curJdbcUrl)
    try {
      val statement = "select create_time, result from " + cacheTable + " where key=?"
      val prep = conn.prepareStatement(statement)
      prep.setString(1, key)
      val rs = prep.executeQuery()
      while (rs.next()) {
        resultList.append((rs.getLong("create_time"), rs.getString("result")))
      }
    }
    finally {
      conn.close()
    }
    val resultListSorted = resultList.sortWith((x, y) => x._1 > y._1)
    if (resultList.isEmpty) null else resultListSorted.head._2

  }

插入一条记录

 /**
    * 插入一条记录
    *
    * @param key    插入的key
    * @param result 插入的result
    */
  def putResult(key: String, result: String): Unit = {
    val curJdbcUrl = jdbcUrl
    val fieldNum = 3
    val placeholder = ("?" * fieldNum).mkString(",")
    val indexTableSql = s"insert into $cacheTable values($placeholder)"
    val conn = DriverManager.getConnection(curJdbcUrl)
    try {
      if (getResult(key) == null) {
        val prep = conn.prepareStatement(indexTableSql)
        prep.setLong(1, new DateTime().getMillis / 1000)
        prep.setString(2, key)
        prep.setString(3, result)
        prep.executeUpdate()
      }
    }
    finally {
      conn.close()
    }
  }

更新一条记录

 /**
    * 更新库表中的一条记录
    *
    * @param key    更新的key
    * @param result 更新的result
    */
  def updateResult(key: String, result: String): Unit = {
    val curJdbcUrl = jdbcUrl
    val indexTableSql = s"update  $cacheTable set result = ? where key = ?"
    val conn = DriverManager.getConnection(curJdbcUrl)
    try {
      if (getResult(key) != null) {
        val prep = conn.prepareStatement(indexTableSql)
        prep.setString(1, result)
        prep.setString(2, key)
        prep.executeUpdate()
      }
    }
    finally {
      conn.close()
    }
  }

下面开始查询多个key，或者插入多个key的操作

批量查询

/**
    * 查询多个secKey对应的结果
    *
    * @param keys 要查询的key数组
    * @return Map[key, result],如果一个key对应多条记录,result为最新的记录
    */
  def getBatchResult(keys: Array[String]): mutable.Map[String, String] = {
    val curJdbcUrl = jdbcUrl
    val resultList = new mutable.ArrayBuffer[(Long, String, String)]
    val conn = DriverManager.getConnection(curJdbcUrl)
    try {
      val keysStr = "'" + keys.mkString("','") + "'"
      val statement = "select create_time, result, key from " + cacheTable + " where key in (" + keysStr + ") order by create_time desc"
      val prep = conn.prepareStatement(statement)
      val rs = prep.executeQuery()
      while (rs.next()) {
        resultList.append((rs.getLong("create_time"), rs.getString("result"), rs.getString("key")))
      }
    }
    finally {
      conn.close()
    }
    val key2ResultMap = new mutable.HashMap[String, String]
    for (record <- resultList) {
      if (!key2ResultMap.contains(record._3))
        key2ResultMap.put(record._3, record._2)
    }
    if (key2ResultMap.size < keys.length) {
      val remain = keys.toSet -- key2ResultMap.keySet
      remain.foreach(key => key2ResultMap.put(key, null))
    }
    key2ResultMap
  }

插入多条记录

/**
    * 插入多条记录
    *
    * @param keys    要插入的keys数组
    * @param results 要插入的result数组
    */
  def putBatchResult(keys: Array[String], results: Array[String]): Unit = {
    val curJdbcUrl = jdbcUrl
    val fieldNum = 3
    val placeholder = ("?" * fieldNum).mkString(",")
    val indexTableSql = s"insert into $cacheTable values($placeholder)"
    val conn = DriverManager.getConnection(curJdbcUrl)
    try {
      for (i <- keys.indices) {
        if (getResult(keys(i)) == null) {
          val prep = conn.prepareStatement(indexTableSql)
          prep.setLong(1, new DateTime().getMillis / 1000)
          prep.setString(2, keys(i))
          prep.setString(3, results(i))
          prep.executeUpdate()
        }
      }
    }
    finally {
      conn.close()
    }
  }