Improve error message for MalformedInputException during resource filtering

[ban-xiu]

Affected version

3.x

Bug description

Issue Description

When Maven's maven-resources-plugin filters resource files, if the file encoding doesn't match the configured encoding, it throws MalformedInputException: Input length = 1. However, the exception message doesn't clearly indicate the encoding issue.

Root Cause

In maven-filtering's FilteringUtils.copyFile() method, Files.newBufferedReader() reads files with the specified encoding. When file bytes don't conform to that encoding, wrapped.read() throws MalformedInputException without including encoding information in the error message.

Minimum reproduction example

project:

encoding-test/
├── pom.xml
└── src/
    └── main/
        └── resources/
            └── test.txt // use gbk

pom:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>encoding-test</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-resources-plugin</artifactId>
                <version>3.5.0</version>
                <configuration>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
        </plugins>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>
</project>

cmd:

 mvn clean resources:resources

log:

[INFO] Scanning for projects...
[INFO] 
[INFO] ---------------------< com.example:encoding-test >----------------------
[INFO] Building encoding-test 1.0-SNAPSHOT
[INFO]   from pom.xml
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] 
[INFO] --- clean:3.2.0:clean (default-clean) @ encoding-test ---
[INFO] Deleting D:\JavaProjects\maven-filtering-coding-test\target
[INFO]
[INFO] --- resources:3.5.0:resources (default-cli) @ encoding-test ---
[INFO] Copying 2 resources from src\main\resources to target\classes
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  2.465 s
[INFO] Finished at: 2026-03-08T16:41:01+08:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-resources-plugin:3.5.0:resources (default-cli) on project encoding-test: filtering D:\JavaProjects\
maven-filtering-coding-test\src\main\resources\test.txt to D:\JavaProjects\maven-filtering-coding-test\target\classes\test.txt failed with MalformedInputException: Input length = 1 -> [Help 1]                                                                                                                                  
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException