From 237d55b3e39f78161d55f411bad380b1acff38d6 Mon Sep 17 00:00:00 2001
From: PJ Fanning <fanningpj@apache.org>
Date: Fri, 15 May 2020 07:36:27 +0000
Subject: [PATCH] [bug-64441] synchronize code that initialises WorkbookFactory

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1877776 13f79535-47bb-0310-9956-ffa450edef68
---
 .../hssf/usermodel/HSSFWorkbookFactory.java   |  4 +++
 .../poi/ss/usermodel/WorkbookFactory.java     | 30 ++++++++++++++++---
 .../xssf/usermodel/XSSFWorkbookFactory.java   |  5 +++-
 3 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/src/java/org/apache/poi/hssf/usermodel/HSSFWorkbookFactory.java b/src/java/org/apache/poi/hssf/usermodel/HSSFWorkbookFactory.java
index 6b041d6a4d..1d826e4c10 100644
--- a/src/java/org/apache/poi/hssf/usermodel/HSSFWorkbookFactory.java
+++ b/src/java/org/apache/poi/hssf/usermodel/HSSFWorkbookFactory.java
@@ -33,6 +33,10 @@ import org.apache.poi.util.Internal;
 public class HSSFWorkbookFactory extends WorkbookFactory {
 
     static {
+        init();
+    }
+
+    public static void init() {
         WorkbookFactory.createHssfFromScratch = HSSFWorkbookFactory::createWorkbook;
         WorkbookFactory.createHssfByNode = HSSFWorkbookFactory::createWorkbook;
     }
diff --git a/src/java/org/apache/poi/ss/usermodel/WorkbookFactory.java b/src/java/org/apache/poi/ss/usermodel/WorkbookFactory.java
index dac35db033..450d21232c 100644
--- a/src/java/org/apache/poi/ss/usermodel/WorkbookFactory.java
+++ b/src/java/org/apache/poi/ss/usermodel/WorkbookFactory.java
@@ -53,6 +53,8 @@ public abstract class WorkbookFactory {
         Workbook apply(T t, U u) throws IOException;
     }
 
+    private static Object hssfLock = new Object();
+    private static Object xssfLock = new Object();
     protected static CreateWorkbook0 createHssfFromScratch;
     protected static CreateWorkbook1<DirectoryNode> createHssfByNode;
 
@@ -333,20 +335,40 @@ public abstract class WorkbookFactory {
 
     private static void initXssf() throws IOException {
         if (createXssfFromScratch == null) {
-            initFactory("org.apache.poi.xssf.usermodel.XSSFWorkbookFactory", "poi-ooxml-*.jar");
+            synchronized (xssfLock) {
+                if (createXssfFromScratch == null) {
+                    String factoryClass = "org.apache.poi.xssf.usermodel.XSSFWorkbookFactory";
+                    Class cls = initFactory(factoryClass, "poi-ooxml-*.jar");
+                    try {
+                        cls.getMethod("init").invoke(null);
+                    } catch (Exception e) {
+                        throw new IOException(factoryClass+" failed to init.");
+                    }
+                }
+            }
         }
     }
 
     private static void initHssf() throws IOException {
         if (createHssfFromScratch == null) {
             // HSSF is part of the main jar, so this shouldn't fail ...
-            initFactory("org.apache.poi.hssf.usermodel.HSSFWorkbookFactory", "poi-*.jar");
+            synchronized (hssfLock) {
+                if (createHssfFromScratch == null) {
+                    String factoryClass = "org.apache.poi.hssf.usermodel.HSSFWorkbookFactory";
+                    Class cls = initFactory(factoryClass, "poi-*.jar");
+                    try {
+                        cls.getMethod("init").invoke(null);
+                    } catch (Exception e) {
+                        throw new IOException(factoryClass+" failed to init.");
+                    }
+                }
+            }
         }
     }
 
-    private static void initFactory(String factoryClass, String jar) throws IOException {
+    private static Class initFactory(String factoryClass, String jar) throws IOException {
         try {
-            Class.forName(factoryClass, true, WorkbookFactory.class.getClassLoader());
+            return Class.forName(factoryClass, true, WorkbookFactory.class.getClassLoader());
         } catch (ClassNotFoundException e) {
             throw new IOException(factoryClass+" not found - check if " + jar + " is on the classpath.");
         }
diff --git a/src/ooxml/java/org/apache/poi/xssf/usermodel/XSSFWorkbookFactory.java b/src/ooxml/java/org/apache/poi/xssf/usermodel/XSSFWorkbookFactory.java
index a997307cab..78fc0805e2 100644
--- a/src/ooxml/java/org/apache/poi/xssf/usermodel/XSSFWorkbookFactory.java
+++ b/src/ooxml/java/org/apache/poi/xssf/usermodel/XSSFWorkbookFactory.java
@@ -31,13 +31,16 @@ import org.apache.poi.ss.usermodel.WorkbookFactory;
 public class XSSFWorkbookFactory extends WorkbookFactory {
 
     static {
+        init();
+    }
+
+    public static void init() {
         WorkbookFactory.createXssfFromScratch = XSSFWorkbookFactory::createWorkbook;
         WorkbookFactory.createXssfByStream = XSSFWorkbookFactory::createWorkbook;
         WorkbookFactory.createXssfByPackage = o -> XSSFWorkbookFactory.createWorkbook((OPCPackage)o);
         WorkbookFactory.createXssfByFile = XSSFWorkbookFactory::createWorkbook;
     }
 
-
     /**
      * Create a new empty Workbook
      *
-- 
2.39.5