fix: reduce memory overhead when loading templates

fesod-sheet/src/main/java/org/apache/fesod/sheet/context/WriteContextImpl.java

@@ -27,6 +27,8 @@
 
 import java.io.File;
 import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
 import java.io.OutputStream;
 import java.util.List;
 import java.util.Map;
@@ -35,6 +37,7 @@
 import java.util.stream.Collectors;
 import lombok.extern.slf4j.Slf4j;
 import org.apache.commons.collections4.MapUtils;
+import org.apache.commons.io.IOUtils;
 import org.apache.fesod.common.util.ListUtils;
 import org.apache.fesod.common.util.StringUtils;
 import org.apache.fesod.sheet.enums.HeaderMergeStrategy;
@@ -128,20 +131,37 @@ public WriteContextImpl(WriteWorkbook writeWorkbook) {
         }
         initCurrentWorkbookHolder(writeWorkbook);
 
-        WorkbookWriteHandlerContext workbookWriteHandlerContext =
-                WriteHandlerUtils.createWorkbookWriteHandlerContext(this);
-        WriteHandlerUtils.beforeWorkbookCreate(workbookWriteHandlerContext);
-        try {
-            WorkBookUtil.createWorkBook(writeWorkbookHolder);
-        } catch (Exception e) {
-            throw new ExcelGenerateException("Create workbook failure", e);
+        try (InputStream template = writeWorkbookHolder.getTempTemplateInputStream()) {
+            WorkbookWriteHandlerContext workbookWriteHandlerContext =
+                    WriteHandlerUtils.createWorkbookWriteHandlerContext(this);
+            WriteHandlerUtils.beforeWorkbookCreate(workbookWriteHandlerContext);
+            try {
+                WorkBookUtil.createWorkBook(writeWorkbookHolder);
+            } catch (Exception e) {
+                throw new ExcelGenerateException("Create workbook failure", e);
+            }
+            WriteHandlerUtils.afterWorkbookCreate(workbookWriteHandlerContext);
+        } catch (IOException e) {
+            closeOnInitializationFailure(e);
+            throw new ExcelGenerateException("Close template failure", e);
+        } catch (Throwable e) {
+            closeOnInitializationFailure(e);
+            throw e;
         }
-        WriteHandlerUtils.afterWorkbookCreate(workbookWriteHandlerContext);
         if (log.isDebugEnabled()) {
             log.debug("Initialization 'WriteContextImpl' complete");
         }
     }
 
+    private void closeOnInitializationFailure(Throwable failure) {
+        IOUtils.closeQuietly(writeWorkbookHolder.getWorkbook(), e -> recordFailure(failure, e));
+        if (writeWorkbookHolder.getAutoCloseStream()) {
+            IOUtils.closeQuietly(writeWorkbookHolder.getOutputStream(), e -> recordFailure(failure, e));
+        }
+        clearEncrypt03();
+        removeThreadLocalCache();
+    }
+
     /**
      * Initializes the current workbook holder with the provided WriteWorkbook.
      *

fesod-sheet/src/main/java/org/apache/fesod/sheet/write/builder/ExcelWriterBuilder.java

@@ -128,26 +128,26 @@ public ExcelWriterBuilder withBom(Boolean withBom) {
     }
 
     /**
-     * Template file.
-     * This file is read into memory, excessive cases can lead to OOM.
+     * Template stream, read through a bounded buffer when the writer is built.
+     * The parsed workbook still resides in memory, so large templates can lead to OOM.
      */
     public ExcelWriterBuilder withTemplate(InputStream templateInputStream) {
         writeWorkbook.setTemplateInputStream(templateInputStream);
         return this;
     }
 
     /**
-     * Template file.
-     * This file is read into memory, excessive cases can lead to OOM.
+     * Template file, read through a bounded buffer when the writer is built.
+     * The parsed workbook still resides in memory, so large templates can lead to OOM.
      */
     public ExcelWriterBuilder withTemplate(File templateFile) {
         writeWorkbook.setTemplateFile(templateFile);
         return this;
     }
 
     /**
-     * Template file.
-     * This file is read into memory, excessive cases can lead to OOM.
+     * Template file, read through a bounded buffer when the writer is built.
+     * The parsed workbook still resides in memory, so large templates can lead to OOM.
      */
     public ExcelWriterBuilder withTemplate(String pathName) {
         return withTemplate(new File(pathName));

fesod-sheet/src/main/java/org/apache/fesod/sheet/write/metadata/WriteWorkbook.java

@@ -73,15 +73,16 @@ public class WriteWorkbook extends WriteBasicParameter {
     private Boolean withBom;
 
     /**
-     * Template input stream
+     * Template input stream, read through a bounded buffer when the writer is built.
+     * The parsed workbook still resides in memory.
      * <p>
      * If 'inputStream' and 'file' all not empty, file first
      */
     private InputStream templateInputStream;
 
     /**
-     * Template file.
-     * This file is read into memory, excessive cases can lead to OOM.
+     * Template file, read through a bounded buffer when the writer is built.
+     * The parsed workbook still resides in memory, so large templates can lead to OOM.
      * <p>
      * If 'inputStream' and 'file' all not empty, file first
      */

fesod-sheet/src/main/java/org/apache/fesod/sheet/write/metadata/holder/WriteWorkbookHolder.java

@@ -25,8 +25,9 @@
 
 package org.apache.fesod.sheet.write.metadata.holder;
 
-import java.io.ByteArrayInputStream;
+import java.io.BufferedInputStream;
 import java.io.File;
+import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
 import java.io.IOException;
@@ -40,15 +41,14 @@
 import lombok.Setter;
 import lombok.ToString.Exclude;
 import lombok.extern.slf4j.Slf4j;
-import org.apache.fesod.common.util.IoUtils;
+import org.apache.commons.io.input.CloseShieldInputStream;
 import org.apache.fesod.common.util.MapUtils;
 import org.apache.fesod.sheet.enums.CellDataTypeEnum;
 import org.apache.fesod.sheet.enums.HolderEnum;
 import org.apache.fesod.sheet.exception.ExcelGenerateException;
 import org.apache.fesod.sheet.metadata.data.DataFormatData;
 import org.apache.fesod.sheet.support.ExcelTypeEnum;
 import org.apache.fesod.sheet.util.DateUtils;
-import org.apache.fesod.sheet.util.FileUtils;
 import org.apache.fesod.sheet.util.StyleUtil;
 import org.apache.fesod.sheet.write.handler.context.WorkbookWriteHandlerContext;
 import org.apache.fesod.sheet.write.metadata.WriteWorkbook;
@@ -129,9 +129,9 @@ public class WriteWorkbookHolder extends AbstractWriteHolder {
      */
     private File templateFile;
     /**
-     * Temporary template file stream.
+     * Buffered template stream, closed after workbook creation.
      * <p>
-     * A temporary file stream needs to be created in order not to modify the original template file.
+     * Kept non-null after closing because it also marks the presence of a template.
      */
     private InputStream tempTemplateInputStream;
     /**
@@ -242,7 +242,7 @@ public WriteWorkbookHolder(WriteWorkbook writeWorkbook) {
         // init handler
         try {
             initHandler(writeWorkbook, null);
-            copyTemplate();
+            prepareTemplate();
         } catch (IOException e) {
             closeOutputStreamOnFailure();
             throw new ExcelGenerateException("Copy template failure.", e);
@@ -289,26 +289,21 @@ private void closeOutputStreamOnFailure() {
         }
     }
 
-    private void copyTemplate() throws IOException {
+    private void prepareTemplate() throws IOException {
         if (writeWorkbook.getTemplateFile() == null && writeWorkbook.getTemplateInputStream() == null) {
             return;
         }
         if (this.excelType == ExcelTypeEnum.CSV) {
             throw new ExcelGenerateException("csv cannot use template.");
         }
-        byte[] templateFileByte = null;
         if (writeWorkbook.getTemplateFile() != null) {
-            templateFileByte = FileUtils.readFileToByteArray(writeWorkbook.getTemplateFile());
-        } else if (writeWorkbook.getTemplateInputStream() != null) {
-            try {
-                templateFileByte = IoUtils.toByteArray(writeWorkbook.getTemplateInputStream());
-            } finally {
-                if (autoCloseStream) {
-                    writeWorkbook.getTemplateInputStream().close();
-                }
-            }
+            this.tempTemplateInputStream =
+                    new BufferedInputStream(new FileInputStream(writeWorkbook.getTemplateFile()));
+        } else {
+            InputStream template = writeWorkbook.getTemplateInputStream();
+            this.tempTemplateInputStream =
+                    new BufferedInputStream(autoCloseStream ? template : CloseShieldInputStream.wrap(template));
         }
-        this.tempTemplateInputStream = new ByteArrayInputStream(templateFileByte);
     }
 
     @Override