从JSNI调用Java方法

Question

I have a class, for instance :

public class Person {

    private String name;

    public Person(String name) {
        this.name = name;
    }

    public void sayName() {
        System.out.println(name);
    }
}

Does it would be work if i call method like this (or where my ingorance or mistake):

public native void someMethod (Person person) /*-{
    person.sayName();
}-*/;

Answer 1

From Accessing Java Methods and Fields from JavaScript documentation:

The syntax is:

[instance-expr.]@class-name::method-name(param-signature)(arguments)

• instance-expr. : must be present when calling an instance method and must be absent when calling a static method

• class-name : is the fully-qualified name of the class in which the method is declared (or a subclass thereof)

• param-signature : is the internal Java method signature as specified at JNI Type Signatures but without the trailing signature of the method return type since it is not needed to choose the overload

• arguments : is the actual argument list to pass to the called method

Here are JNI Type Signatures:

Type Signature               Java Type
Z                            boolean
B                            byte
C                            char
S                            short
I                            int
J                            long
F                            float
D                            double
L fully-qualified-class ;    fully-qualified-class
[ type                       type[]
( arg-types ) ret-type       method type

For example, the Java method:

long f (int n, String s, int[] arr); 
has the following type signature:

(ILjava/lang/String;[I)J

In your case (no parameters) it would be:

public native void someMethod (Person person) /*-{
    person.@your.package.name.client.Person::sayName()();
}-*/;

Replace your.package.name with a real package name.

Answer 2

package org.example.foo;
public class Flipper {

  public native void flipName(String name) /*-{
    var re = /(\w+)\s(\w+)/;
    var s = name.replace(re, '$2, $1');
    this.@org.example.foo.Flipper::onFlip(Ljava/lang/String;)(s);
  }-*/;

  private void onFlip(String flippedName) {
   // do something useful with the flipped name
  }
}