Same source code, Eclipse build success but Maven (javac) fails

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鱼传尺愫
鱼传尺愫 2021-02-15 11:07

Keep getting this error when compiling using Maven:

type parameters of X cannot be determined; no unique maximal instance exists for type variable X wit         


        
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  • 2021-02-15 11:15

    This issue can occur when your code is generic and it calls another method that has a generic return type. Sometimes the compiler gets confused trying to figure out how to resolve the method call / return type.

    It can be resolved by adding an explicit cast to your code.

    // Old code:
    public T getValue() {
        return otherMethod();  // otherMethod has the signature: <RT> RT otherMethod() { ... }
    }
    
    // New code:
    @SuppressWarnings("unchecked")
    public T getValue() {
        return (T) otherMethod();   // the cast tells the compiler what to do.
    }
    
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  • 2021-02-15 11:19

    A few things to look at:

    1. Both Eclipse and Maven are using the same java/bin installation
    2. Eclipse and Maven are using the same libraries, one might have something the other does not.
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  • 2021-02-15 11:19

    It definitely has to do something with the JDK versions maven and eclipse are using. Also make sure your Compiler compliance level in eclipse points to the right JDK version.

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  • 2021-02-15 11:32

    I met the same error,use ant. Because when compile by ant or maven,javac use JDK to compile.But in eclipse,it has JDT,that can compile success.

    I add below script in my build.xml file: <property name="build.compiler" value="org.eclipse.jdt.core.JDTCompilerAdapter" /> Then,ant can build success.

    I am not familiar with Maven. Maybe,it can set the compiler?

    In my source code,there are many code like this: public <X> X find(String hql, Object... values) { return (X) HibernateUtils.createQuery(getSession(), hql, values).uniqueResult(); }

    Maybe your code too.

    But,use JDT,the success is't the final success,in ant. build.xml can build success only in eclipse. when I run ant from windows command,fail. Throw another error: Class not found: org.eclipse.jdt.core.JDTCompilerAdapter

    PS, I have copy jar files about JDT in eclipse plugin to ant_home/lib directory.

    Wish a little help to you.And our problem can solve.

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