java-native-access/jna · error · java.lang.IllegalArgumentException

No suitable constructor found for class:

Error message

No suitable constructor found for class: 

What it means

Structure.validate(Class) ensures a Structure subclass has a public no-arg constructor, which JNA needs to reflectively instantiate the class (e.g. for auto-allocation, newInstance, nested arrays). If cls.getConstructor() throws NoSuchMethodException (or is blocked by SecurityException), it throws IllegalArgumentException with the class name.

Source

Thrown at src/com/sun/jna/Structure.java:2413

    /** Placeholder pointer to help avoid auto-allocation of memory where a
     * Structure needs a valid pointer but want to avoid actually reading from it.
     */
    private static final Pointer PLACEHOLDER_MEMORY = new Pointer(0) {
        @Override
        public Pointer share(long offset, long sz) { return this; }
    };

    /** Indicate whether the given Structure class can be created by JNA.
     * @param cls Structure subclass to check
     */
    static void validate(Class<? extends Structure> cls) {
        try {
            cls.getConstructor();
            return;
        }catch(NoSuchMethodException | SecurityException e) {
        }
        throw new IllegalArgumentException("No suitable constructor found for class: " + cls.getName());
    }
}

View on GitHub (pinned to d036ad9781)

Solutions

1. Add an explicit public no-arg constructor to the Structure subclass (keep any parameterized ones as extras)
2. Make the class a top-level or static nested class so its no-arg constructor is accessible without an enclosing instance
3. Ensure the no-arg constructor is public and not blocked by a SecurityManager; grant reflect access or remove the restrictive policy
4. Initialize fields in the no-arg constructor or via field initializers so JNA's reflective instantiation produces a valid struct

Example fix

// before
public class Point extends Structure {
    public Point(int x, int y) { ... } // no no-arg constructor
}
// after
public class Point extends Structure {
    public int x, y;
    public Point() {}
    public Point(int x, int y) { this.x = x; this.y = y; }
}

void validateStructureClass(Class<? extends Structure> cls) {
    if (!cls.isMemberClass() || java.lang.reflect.Modifier.isStatic(cls.getModifiers())) {
        try { cls.getConstructor(); }
        catch (NoSuchMethodException e) {
            throw new IllegalArgumentException(cls + " needs a public no-arg constructor");
        }
    }
}

boolean hasPublicNoArgCtor(Class<?> c) {
    try { return java.lang.reflect.Modifier.isPublic(c.getConstructor().getModifiers()); }
    catch (NoSuchMethodException e) { return false; }
}

try {
    MyStruct[] arr = (MyStruct[]) new MyStruct().toArray(n);
} catch (IllegalArgumentException e) {
    if (e.getMessage() != null && e.getMessage().startsWith("No suitable constructor")) {
        throw new IllegalStateException("Add a public no-arg constructor to " + e.getMessage());
    }
    throw e;
}

When it happens

Trigger: Defining a Structure subclass with only parameterized constructors, a private/protected no-arg constructor, or an anonymous/local Structure class lacking an accessible no-arg constructor, then having JNA instantiate it reflectively (toArray, nested structures, Structure.newInstance).

Common situations: Adding a convenience constructor with arguments and removing the implicit default constructor, using a SecurityManager that blocks reflective access to the class, or declaring nested Structure classes as non-static inner classes whose constructors require an enclosing instance.

Related errors

• Instantiation of " + type + " (Pointer) not allowed, is it p
• Exception thrown while instantiating an instance of " + type
• Can't create an instance of <klass>, requires a public no-ar
• This VM does not support read-only fields (field '" + field.
• Exception reading field '" + f.getName() + "' in " + getClas

AI-assisted analysis of java-native-access/jna@d036ad9781 (2026-09-12). Data as JSON: /api/errors/d912635531db4c2c. Report an issue: GitHub.