使用R连接JIRA时遇class not found错误，求解决方法

Let's break down the issue and walk through the most likely fixes for your "class not found" error.

Context #

First, let's recap your setup to ensure we're on the same page:

• R version: 3.4.1 (64-bit Windows)
• Installed packages: RJDBC, DBI, rJava, cdata, wrapr (all built under newer R versions, leading to version mismatch warnings)
• The error triggers when running this code:

driver <- JDBC(driverClass = "cdata.jdbc.jira.JiraDriver", classPath = "MyInstallationDir//lib//cdata.jdbc.jira.jar", identifier.quote = "'")

• Error message:

Error in .jfindClass(as.character(driverClass)[1]) : class not found

Step 1: Fix the Driver Class Name (Most Likely Culprit) #

CData's JDBC driver for JIRA uses cdata.jdbc.jira.JIRADriver (note the uppercase JIRA instead of Jira) as the official driver class name. This is a common typo that immediately causes the "class not found" error. Update your driverClass parameter to match:

driverClass = "cdata.jdbc.jira.JIRADriver"

Step 2: Verify the JAR File Path #

Double-check that your classPath points to the actual location of the CData JIRA driver JAR file:

• Replace MyInstallationDir with the full path to your CData installation (e.g., C://Program Files//CData//CData JDBC Driver for JIRA//lib//cdata.jdbc.jira.jar)
• Ensure the path uses forward slashes (/) or double backslashes (\\) correctly (your current // should work, but confirm the directory and JAR file exist on your system)

Step 3: Resolve Package Version Mismatches #

Your packages are built under newer R versions (3.4.3/3.4.4) than your installed 3.4.1. While these warnings might not directly cause the class error, they can lead to unexpected behavior down the line. To fix this:

• Recommended: Upgrade your R version to 3.4.4 or later (older versions are no longer supported, so this will prevent future compatibility issues)
• Alternatively, reinstall the packages using your current R version to eliminate the warnings:

install.packages(c("RJDBC", "DBI", "rJava", "cdata", "wrapr"))

Step 4: Ensure rJava is Properly Configured #

rJava is the backbone of JDBC connections in R. Make sure:

• You have a 64-bit Java Runtime Environment (JRE) installed (matching your 64-bit R version)
• If rJava can't find your JRE automatically, set the JAVA_HOME environment variable before loading the package:

Sys.setenv(JAVA_HOME="C://Program Files//Java//jre1.8.0_301") # Replace with your actual JRE path
library(rJava)
library(RJDBC)

Step 5: Test the Corrected Code #

Putting it all together, here's the adjusted connection code to try:

# Set Java home if needed
Sys.setenv(JAVA_HOME="C://Program Files//Java//jre1.8.0_301")

# Load required packages in order
library(rJava)
library(DBI)
library(RJDBC)

# Initialize the driver with correct class and path
driver <- JDBC(
  driverClass = "cdata.jdbc.jira.JIRADriver",
  classPath = "C://Program Files//CData//CData JDBC Driver for JIRA//lib//cdata.jdbc.jira.jar",
  identifier.quote = "'"
)

Bonus: Include All Dependent JARs #

If you still get the error, some CData drivers require additional dependent JARs in the lib directory. Load all JARs instead of just the main one:

# Get all JAR files in the CData lib folder
classPath <- list.files("C://Program Files//CData//CData JDBC Driver for JIRA//lib", pattern = "\\.jar$", full.names = TRUE)

# Initialize driver with all JARs
driver <- JDBC(
  driverClass = "cdata.jdbc.jira.JIRADriver",
  classPath = classPath,
  identifier.quote = "'"
)

内容的提问来源于stack exchange，提问作者Tushar