Question

我在Windows 7 x64上使用Apache Spark 1.4.0，使用Java 1.8.0_45 x64，在IPython 3.2.0中使用Python 2.7.10 x86

我正在尝试在IPython笔记本中编写一个基于DataFrame的程序，该程序可以读取和写回SQL Server数据库。

到目前为止，我可以从数据库中读取数据

from pyspark.sql import SQLContext
sqlContext = SQLContext(sc)
df = sqlContext.load(source="jdbc",url="jdbc:sqlserver://serverURL", dbtable="dbName.tableName", driver="com.microsoft.sqlserver.jdbc.SQLServerDriver", user="userName", password="password")

并将数据转换为熊猫并做任何我想做的事情。（这不仅有点麻烦，而且在将spark的默认情况下将Microsoft的sqljdbc42.jar添加到spark.driver.extraClassPath之后也能正常工作）

当我使用DataFrameWriter API将数据写回SQL Server时出现了当前的问题：

df.write.jdbc("jdbc:sqlserver://serverURL", "dbName.SparkTestTable1", dict(driver="com.microsoft.sqlserver.jdbc.SQLServerDriver", user="userName", password="password"))

---------------------------------------------------------------------------
Py4JError                                 Traceback (most recent call last)
<ipython-input-19-8502a3e85b1e> in <module>()
----> 1 df.write.jdbc("jdbc:sqlserver://jdbc:sqlserver", "dbName.SparkTestTable1", dict(driver="com.microsoft.sqlserver.jdbc.SQLServerDriver", user="userName", password="password"))

C:\Users\User\Downloads\spark-1.4.0-bin-hadoop2.6\python\pyspark\sql\readwriter.pyc in jdbc(self, url, table, mode, properties)
    394         for k in properties:
    395             jprop.setProperty(k, properties[k])
--> 396         self._jwrite.mode(mode).jdbc(url, table, jprop)
    397 
    398 

C:\Python27\lib\site-packages\py4j\java_gateway.pyc in __call__(self, *args)
    536         answer = self.gateway_client.send_command(command)
    537         return_value = get_return_value(answer, self.gateway_client,
--> 538                 self.target_id, self.name)
    539 
    540         for temp_arg in temp_args:

C:\Python27\lib\site-packages\py4j\protocol.pyc in get_return_value(answer, gateway_client, target_id, name)
    302                 raise Py4JError(
    303                     'An error occurred while calling {0}{1}{2}. Trace:\n{3}\n'.
--> 304                     format(target_id, '.', name, value))
    305         else:
    306             raise Py4JError(

Py4JError: An error occurred while calling o49.mode. Trace:
py4j.Py4JException: Method mode([class java.util.HashMap]) does not exist
    at py4j.reflection.ReflectionEngine.getMethod(ReflectionEngine.java:333)
    at py4j.reflection.ReflectionEngine.getMethod(ReflectionEngine.java:342)
    at py4j.Gateway.invoke(Gateway.java:252)
    at py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:133)
    at py4j.commands.CallCommand.execute(CallCommand.java:79)
    at py4j.GatewayConnection.run(GatewayConnection.java:207)
    at java.lang.Thread.run(Unknown Source)

问题似乎是py4j在将我的connectionProperties字典转换为JVM对象时找不到Java java.util.HashMap类。将我的rt.jar（带路径）添加到spark.driver.extraClassPath并不能解决问题。从write命令中删除字典可以避免此错误，但当然由于缺少驱动程序和身份验证而导致写入失败。

编辑：错误的o49.mode部分从运行变为运行。

Answer 1

Davies Liu在Spark用户邮件列表found the problem上。我错过了Scala和Python API之间的细微差别。您必须传入模式字符串（例如“overwrite”）作为Python API中的第3个参数，而不是Scala API。如下更改语句可以解决此问题：

df.write.jdbc("jdbc:sqlserver://serverURL", "dbName.SparkTestTable1", "overwrite", dict(driver="com.microsoft.sqlserver.jdbc.SQLServerDriver", user="userName", password="password"))

PySpark会话中缺少java.util.HashMap

1 个答案: