在使用jaydebeapi只连接一种数据库时，是没问题的，但是如果需要同时连接两种数据库，比如同时连接oracle和mysql
例如以下测试代码：
import jaydebeapi ##使用jdbc驱动连接数据库
import pandas as pd
dirver='oracle.jdbc.driver.OracleDriver'
jarFile='D:\\WORK\\PYScript\\BiDataMonitor\\jdbc\\64\\ojdbc14.jar'
addr_='xxx.xxx.xxx.xxx'+':'+'1521'+'/'+'xxx'
url='jdbc:oracle:thin:@'+addr_
print('url',url)
DBUser='用户名'
DBPwd='密码'
conn=jaydebeapi.connect(dirver,[url,DBUser,DBPwd],jarFile) ##使用jdbc驱动连接数据库
sql_str="select 'oracle' from dual"
df=pd.read_sql_query(sql_str,conn)
print(df)
conn.close()
dirver='com.mysql.jdbc.Driver'
jarFile='D:\\WORK\\PYScript\\BiDataMonitor\\jdbc\\64\\mysql-connector-java-5.1.30.jar'
addr_='xxx.xxx.xxx.xxx'+':'+'3306'+'/'+'xxx'
url='jdbc:mysql://'+addr_
print('url',url)
DBUserMySql='用户名'
DBPwdMySql='密码'
conn2=jaydebeapi.connect(dirver,[url,DBUserMySql,DBPwdMySql],jarFile)
sql_str="select 'mysql' from dual"
df=pd.read_sql_query(sql_str,conn2)
print(df)
conn2.close()在连接第二种数据库时，就会报错误：
Py4JJavaError: An error occurred while calling z:java.sql.DriverManager.getConnection.
: java.sql.SQLException: No suitable driver found for jdbc:mysql://10.1.164.5:3306/vvm
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at py4j.reflection.MethodInvoker.invoke(MethodInvoker.java:244)
at py4j.reflection.ReflectionEngine.invoke(ReflectionEngine.java:357)
at py4j.Gateway.invoke(Gateway.java:282)
at py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:132)
at py4j.commands.CallCommand.execute(CallCommand.java:79)
at py4j.GatewayConnection.run(GatewayConnection.java:214)
at java.lang.Thread.run(Unknown Source)错误信息中显示，找不到渠道，而实际上并不是驱动或者jar包的问题。
要分析和解决这个问题，还需要从jaydebeapi的源码中分析，打开jaydebeapi源码（下载地址：https://pypi.python.org/pypi/JayDeBeApi3），从报错信息中我们可以得到，是在...jaydebeapi\__init__.py", line 68
jaydebeapi.connect方法源码如下：
# DB-API 2.0 Module Interface connect constructor
def connect(jclassname, driver_args, jars=None, libs=None):
"""Open a connection to a database using a JDBC driver and return
a Connection instance.
jclassname: Full qualified Java class name of the JDBC driver.
driver_args: Argument or sequence of arguments to be passed to the
Java DriverManager.getConnection method. Usually the
database URL. See
http://docs.oracle.com/javase/6/docs/api/java/sql/DriverManager.html
for more details
jars: Jar filename or sequence of filenames for the JDBC driver
libs: Dll/so filenames or sequence of dlls/sos used as shared
library by the JDBC driver
"""
if _gateway_is_running():
gateway = java_gateway.JavaGateway()
else:
driver_args = [driver_args] if isinstance(driver_args, str) else driver_args
if jars:
classpath = os.pathsep.join(jars) if isinstance(jars, list) else jars
else:
classpath = None
if libs:
javaopts = libs if isinstance(libs, list) else [libs]
else:
javaopts = []
gateway = java_gateway.JavaGateway.launch_gateway(
port=25333, classpath=classpath, javaopts=javaopts, die_on_exit=True)
java_gateway.java_import(gateway.jvm, 'java.sql.DriverManager')
gateway.jvm.Class.forName(jclassname)
connection = gateway.jvm.DriverManager.getConnection(*driver_args)
if _converters is None:
types_map = {}
for type in gateway.jvm.Class.forName("java.sql.Types").getFields():
types_map[type.getName()] = type.getInt(None)
_init_converters(types_map)
return Connection(connection, _converters)报错信息中提示的68行也就是：
connection = gateway.jvm.DriverManager.getConnection(*driver_args)其实，我不需要跟深层次是剖析，只需要分析下jaydebeapi.connect方法即可，该方法大概是逻辑是：
判断 java_gateway是否running
|----------是---|-----否-----|
| |
获取gateway实例 1、初始化参数
2、创建gateway实例问题就出在这里，第一次连接oracle时，通过右边分支先初始化参数，然后创建了gateway实例，但是第二次调用jaydebeapi.connect方法连mysql时，由于_gateway_is_running()返回真，所以走左边分支，直接获取了上一次连接oracle时创建gateway实例，其中最重要的两个个参数jclassname和classpath，也就是“oracle.jdbc.driver.OracleDriver”和"ojdbc14.jar"
gateway = java_gateway.JavaGateway.launch_gateway(
port=25333, classpath=classpath, javaopts=javaopts, die_on_exit=True)
java_gateway.java_import(gateway.jvm, 'java.sql.DriverManager')
gateway.jvm.Class.forName(jclassname)而第二次连mysql时，用的是mysql的连接，所以当然就是报No suitable driver found for jdbc错误。
明白了报错的原因，下面就来需求解决方法
解决的方法应该有多种，我这里采取了最简单，最暴力的方法，就是在判断_gateway_is_running()时，将其关闭，然后重新重建新的gateway实例，这样虽然简单，但是如果频繁连接数据库时，就会因为不能重用上一次实例而消耗额外的资源。
通过帮助函数可知，gateway实例有一个shutdown方法
修改后的connect方法如下：
# DB-API 2.0 Module Interface connect constructor
def connect(jclassname, driver_args, jars=None, libs=None):
"""Open a connection to a database using a JDBC driver and return
a Connection instance.
jclassname: Full qualified Java class name of the JDBC driver.
driver_args: Argument or sequence of arguments to be passed to the
Java DriverManager.getConnection method. Usually the
database URL. See
http://docs.oracle.com/javase/6/docs/api/java/sql/DriverManager.html
for more details
jars: Jar filename or sequence of filenames for the JDBC driver
libs: Dll/so filenames or sequence of dlls/sos used as shared
library by the JDBC driver
"""
if _gateway_is_running():
gateway = java_gateway.JavaGateway()
gateway.shutdown()
else:
pass
driver_args = [driver_args] if isinstance(driver_args, str) else driver_args
if jars:
classpath = os.pathsep.join(jars) if isinstance(jars, list) else jars
else:
classpath = None
if libs:
javaopts = libs if isinstance(libs, list) else [libs]
else:
javaopts = []
gateway = java_gateway.JavaGateway.launch_gateway(
port=25333, classpath=classpath, javaopts=javaopts, die_on_exit=True)
java_gateway.java_import(gateway.jvm, 'java.sql.DriverManager')
gateway.jvm.Class.forName(jclassname)
connection = gateway.jvm.DriverManager.getConnection(*driver_args)
if _converters is None:
types_map = {}
for type in gateway.jvm.Class.forName("java.sql.Types").getFields():
types_map[type.getName()] = type.getInt(None)
_init_converters(types_map)
return Connection(connection, _converters)然后卸载jaydebeapi，用修改后的源码重新安装一次即可，源码安装方法，可以查看之前的一篇博客：
https://blog.csdn.net/cakecc2008/article/details/79073181