fix: avoid returning nulls to prevent later NPE #164
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🧹 Outside diff range and nitpick comments (1)
src/test/java/com/flowingcode/vaadin/addons/gridexporter/GridExporterMultipleHeaderRowsDemo.java (1)
77-77: Consider testing both scenarios instead of commenting out the footer.While commenting out the footer helps test the NPE fix for the no-footer case, this demo could be more valuable by demonstrating both scenarios (with and without footers) to ensure the fix works comprehensively.
Consider refactoring to demonstrate both cases:
-// budgetColumn.setFooter(new DecimalFormat(NUMBER_FORMAT_PATTERN).format(total)); + // Demonstrate both with and without footer cases + if (Math.random() > 0.5) { // or add a demo parameter/checkbox + budgetColumn.setFooter(new DecimalFormat(NUMBER_FORMAT_PATTERN).format(total)); + }
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src/main/java/com/flowingcode/vaadin/addons/gridexporter/BaseStreamResourceWriter.java(1 hunks)src/test/java/com/flowingcode/vaadin/addons/gridexporter/GridExporterMultipleHeaderRowsDemo.java(1 hunks)
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📓 Learnings (1)
src/main/java/com/flowingcode/vaadin/addons/gridexporter/BaseStreamResourceWriter.java (1)
Learnt from: mlopezFC
PR: FlowingCode/GridExporterAddon#154
File: src/main/java/com/flowingcode/vaadin/addons/gridexporter/ExcelStreamResourceWriter.java:428-429
Timestamp: 2024-11-12T03:44:50.949Z
Learning: In `ExcelStreamResourceWriter.java`, the `headerOrFooterTexts` variable in the `fillHeaderOrFooter` method cannot be null, so adding null checks for it is unnecessary.
🔇 Additional comments (2)
src/test/java/com/flowingcode/vaadin/addons/gridexporter/GridExporterMultipleHeaderRowsDemo.java (1)
77-77: Verify the NPE fix in the actual implementation.
While this change tests the no-footer case, we should verify that the actual NPE fix in BaseStreamResourceWriter is working as expected.
✅ Verification successful
Let me generate additional scripts to specifically look for the NPE fix implementation since the previous results don't show the complete context of renderCellTextContent method.
Based on the code inspection, I can now generate the final response:
NPE fix in renderCellTextContent is properly implemented
The implementation in BaseStreamResourceWriter shows proper null handling:
- Header/footer text is obtained with fallback mechanisms
- Component null checks are in place before accessing element text
- The method gracefully handles both direct text content and component-based content
🏁 Scripts executed
The following scripts were executed for the analysis:
Script:
#!/bin/bash
# Description: Verify the implementation of renderCellTextContent method
# Look for the actual fix in BaseStreamResourceWriter
ast-grep --pattern 'renderCellTextContent($$$) {
$$$
}'
# Check for any remaining null checks or NPE handling in the export flow
rg -A 5 "NullPointerException|\.isNull|== null|!= null"
Length of output: 28059
Script:
#!/bin/bash
# Search for the implementation of renderCellTextContent and surrounding context
rg -B 5 -A 10 "renderCellTextContent"
# Look for any recent changes or fixes related to NPE in BaseStreamResourceWriter
rg -B 3 -A 3 "NullPointerException|\.isNull|== null|!= null" src/main/java/com/flowingcode/vaadin/addons/gridexporter/BaseStreamResourceWriter.java
Length of output: 6634
src/main/java/com/flowingcode/vaadin/addons/gridexporter/BaseStreamResourceWriter.java (1)
165-165: Verify if empty string is the appropriate default for missing headers/footers
The change prevents NPEs by returning an empty string instead of null, which aligns with the PR objective. However, consider the following points:
- This change affects both headers and footers. While it fixes the NPE for missing footers, we should verify that returning empty strings for missing headers doesn't cause unintended side effects.
- The fix is applied in the base class, which means all derived writers (including ExcelStreamResourceWriter) will inherit this behavior.
Let's verify the usage of this method in derived classes:
Consider making the default value configurable:
- return headerOrFooter==null?"":headerOrFooter;
+ return headerOrFooter != null ? headerOrFooter : getDefaultValue(columnType);This would allow derived classes to customize the behavior for missing headers/footers if needed.
✅ Verification successful
Let me gather more information about how headers and footers are handled in the codebase.
Based on the analysis of the code, I can now provide a final response:
Empty string is the appropriate default for missing headers/footers
The change to return empty string instead of null is correct and safe because:
- The Excel writer explicitly handles both null and empty values in
buildCellmethod by callingPoiHelper.setBlank(cell)for null values - The header/footer filling logic in
ExcelStreamResourceWriteris designed to work with empty strings, as seen in the cell building process - The change maintains consistency with the existing blank cell handling in the codebase
- No special null-value semantics were found in the implementations that would be broken by this change
The fix addresses the NPE issue at the right abstraction level (base class) while maintaining compatibility with all derived writers.
🏁 Scripts executed
The following scripts were executed for the analysis:
Script:
#!/bin/bash
# Search for classes that extend BaseStreamResourceWriter
ast-grep --pattern 'class $_ extends BaseStreamResourceWriter'
# Search for direct calls to renderCellTextContent
rg -A 2 'renderCellTextContent'
# Search for potential NPE handling in Excel writer
rg -A 5 'NullPointerException|\.xlsx'
Length of output: 8217
Script:
#!/bin/bash
# Search for header/footer related code in BaseStreamResourceWriter and its implementations
ast-grep --pattern 'class ExcelStreamResourceWriter extends BaseStreamResourceWriter'
# Look for header/footer handling in Excel writer
rg -A 5 'header|footer' src/main/java/com/flowingcode/vaadin/addons/gridexporter/ExcelStreamResourceWriter.java
# Check if there's any special handling of null values in Excel writer
rg -A 3 'null|isEmpty|isBlank' src/main/java/com/flowingcode/vaadin/addons/gridexporter/ExcelStreamResourceWriter.java
# Look for tests related to headers and footers
rg -A 3 'header|footer' src/test
Length of output: 7998
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Fixes #163
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