[FIXED] Java file: Content not allowed in prolog

Issue

I'm new to Spring and started using the Sprint Tool Suite (eclipse) and see this error in a java file in my maven project: "Content is not allowed in prolog". This prevents the class from compiling (which is just a minimal SpringBootApplication class) in eclipse.

package com.test;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

I've scoured the web and saw that in virtually every reference, this is an XML-parsing error. I had been updating three XML files but didn't see any invisible characters before the <?xml in a hex editor. They all specify to use UTF-8 encoding and I'm not seeing alternating 0 bytes that would indicate an accidental UTF-16 encoding. The line endings seem consistent (just a line feed).

Interestingly, it builds without compiler errors with "maven clean install". I don't see any special characters in the java file either, but eclipse tells me that file is the problem and that's it a spring beans problem. The error message shows on the first line with the package statement.

Any ideas what the root problem is or how I can solve this?

Update As requested, here's my pom.xml file:

<?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>org.springframework</groupId>
    <artifactId>gs-rest-service</artifactId>
    <version>0.1.0</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.2.5.RELEASE</version>
    </parent>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.2.8</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
    </dependencies>

    <properties>
        <java.version>1.8</java.version>
    </properties>


    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
       <resources>
         <resource>
           <targetPath>com/test/mybatis/mappers</targetPath>
           <directory>src/main/java/com/test/mybatis/mappers</directory>
           <includes>
             <include>*.xml</include>
           </includes>
         </resource>
         <resource>
           <directory>src/main/resources</directory>
         </resource>
       </resources>
    </build>

    <repositories>
        <repository>
            <id>spring-releases</id>
            <url>https://repo.spring.io/libs-release</url>
        </repository>
    </repositories>
    <pluginRepositories>
        <pluginRepository>
            <id>spring-releases</id>
            <url>https://repo.spring.io/libs-release</url>
        </pluginRepository>
    </pluginRepositories>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>5.1.36</version>
            </dependency>
        </dependencies>
    </dependencyManagement>
</project>

Update 2 I searched my project folder for all .xml files and have removed all invisible characters programmatically using perl -i -pe 's/[^\x20-\x7f\x0A\x09]//g' fileName, but there were no invisible characters. This confirms what I saw in the hex editor.

Two questions come to mind: Why is the error showing in a .java file instead of a. xml file? Why is this only a problem for eclipse and not maven?

The eclipse log shows this message (which indicates a .xml file):

org.xml.sax.SAXParseException; lineNumber: 1; columnNumber: 1; Content is not allowed in prolog.
    at org.apache.xerces.parsers.DOMParser.parse(Unknown Source)
    at org.springframework.ide.eclipse.core.io.xml.XercesDocumentLoader.loadDocument(XercesDocumentLoader.java:48)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadDocument(XmlBeanDefinitionReader.java:429)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:391)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:336)
    at org.springframework.ide.eclipse.beans.core.internal.model.BeansConfig$2.loadBeanDefinitions(BeansConfig.java:397)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:304)
    at org.springframework.ide.eclipse.beans.core.internal.model.BeansConfig$3.call(BeansConfig.java:456)
    at org.springframework.ide.eclipse.beans.core.internal.model.BeansConfig$3.call(BeansConfig.java:1)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

Update 3 I did find some eclipse-generated xml files in my workspace with characters before the <?xml using grep -ERl '^[^=]+<\?xml' . which ignores some of the eclipse user prefs which have xml embedded in the lines of the file. After removing the extra characters, the problem remained though.

Think I may restart the project and copy over files one at a time.

Solution

It seems likely that the culprit was a corrupted eclipse workspace. I created a new workspace and imported the project and everything works fine. That would also explain why an external maven build didn't show any problems.

As noted in update 3, I had found some eclipse-generated xml files that had characters before the prolog. Although correcting those did not fix the problems, I didn't inspect every eclipse file with xml content (like the user prefs) to see if they had some invisible characters before the prolog.

Don't know what would have caused it to be corrupted except for perhaps force quitting eclipse during an unresponsive maven repo update but I can't be certain if that's when my troubles started. I'm just glad I can move forward.

Answered By - rimsky