Resin 1.1
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Java Wrapping
Wrapping Java objects
To give Java objects a JavaScript interface, Resin wraps the Java with automatically generated classes. The wrapper classes convert between Java and JavaScript types, mashalling and unmarshalling call arguments. Resin's wrapping tries to abide by the rule of least surprises. Wrapped objects as a developer expects. However, because of the differences between Java and JavaScript, the details of making them mesh are somewhat lengthy.
Packages
The `Packages` object lets scripts directly access Java classes. The properties of the `Packages` object are Java packages and classes. As a convenience, the variable 'java' is preset to 'Packages.java' and 'caucho' is preset to 'Packages.com.caucho'.
Java Vector
a = new Packages.java.util.Vector(); a.addElement("a"); a.addElement("b");
Resin to Java
The pseudo-code in the following tables are based on the EcmaScript definitions.
Resin to Java
Java Type | pseudo-code
--- | ---
boolean | obj.toBoolean()
byte | (byte) obj.toInt32()
short | (short) obj.toInt32()
char | obj.toString()[0]
int | obj.toInt32()
long | (long) obj.toNumber()
float | (float) obj.toNumber()
double | obj.toNumber()
String | obj.toString()
Object | obj.toJavaObject()
toJavaObject
JavaScript | Java
--- | ---
null | null
undefined | null
boolean | java.lang.Boolean
date | java.lang.Date
string | java.lang.String
number | java.lang.Double
wrapper | wrapper contents
regexp | com.caucho.regexp.Regexp
Object | unchanged, com.caucho.es.ESBase
Java to Resin
Note: Java `Number`'s are converted to JavaScript numbers, so the `Number` object is not preserved.
Java to Resin
Java | JavaScript
--- | ---
null | null
boolean | boolean
byte | number
short | number
char | string
int | number
long | number
float | number
double | number
java.lang.String | string
java.util.Date | date
java.lang.Number | number
Object | Object wrapper
Methods
Scripts can call methods on the wrapped object. Each method is wrapped in a JavaScript function but will only work when `this` is the wrapped object.
map = new java.util.HashMap(); map.put("foo", "bar"); writeln(map.get); writeln(map.get("foo")); writeln(map.get("bar"));
function get() { [native code] } bar null
### Method Overloading Methods may be overloaded by argument length. Methods may not be overloaded by argument type. Type-overloaded methods are ignored. For example, the `StringBuffer` append call is not available in Resin. ### Method Calls Method calls follow these steps: Select overloaded method by argument length Convert JavaScript arguments to Java Call the method Convert any Java return value to JavaScript
Properties
Resin exposes several types of properties to the script: fields, simple bean get/set properties, bean indexed properties, and named properties. Fields always take precedence. ### Fields Resin exposes public Java fields as properties. Wrapped instances can access object and static properties, while wrapped classes can only access static properties. Note: Fields override design pattern properties, i.e. bean properties.
Test.java
public class Test { public static int foo = 3; public int bar = 9; }
test.es
Test = Packages.Test; t = new Test(); writeln("Test " + Test.foo + " " + Test.bar); writeln(Test.bar); writeln("test " + t.foo + " " + t.bar);
Test 3 undefined test 3 9
### Simple Bean Properties The bean properties are a convenience for some common method patterns. In all cases, the method interface always exists. Methods matching `foo getXXX()` and `void setXXX(foo a)` are treated as simple JavaScript properties.
Test.java
public class Test { private int a = 19; public int getA() { return a; } public void setA(int value) { a = value } }
test.es
t = new Packages.Test(); writeln(t.a); t.a++; writeln(t.a);
19 20
### Indexed Bean Properties Resin treats indexed properties as arrays using an extensions of the Bean indexed property pattern. In addition to the `Foo getXXX(int)` and `void setXXX(int, Foo)` methods, Resin will use `int getXXXLength()` to determine an array length.
Test.java
public class Test { String []data = new String[4] { "fee", "fie", "foe", "fum"}; public String getString(int i) { return data[i]; } public void setString(int i, String value) { data[i] = value; } public int getStringLength() { return data.length; } }
test.es
test = new Packages.Test(); writeln(test.string[0] + " " + test.string[test.length - 1]); writeln(test.reverse().join());
fee fum fum,foe,fie,fee
### Named Bean Properties Resin treats named properties as objections extending the Bean properties. It the named properties recognize the `Foo getXXX(int)` and `void setXXX(int, Foo)` methods, Resin will use `Iterator getXXXNames()` to iterate through the members of the property.
Java Def | Java Call | JavaScript
--- | --- | ---
String getFoo(String name) | test.getFoo("bar") | test.foo.bar
void setFoo(String name, String value) | test.setFoo("bar", "fie") | test.foo.bar = "fie";
Iterator getFooNames() | test.getFooNames() | for (name in test.foo) { ... }
Test.java
public class Test { HashMap data = new HashMap(); public String getFoo(String name) { return data.get(name); } public void setFoo(String name, String value) { data.set(name, value); } public Iterator getFooNames() { return data.keySet().iterator(); } }
test.es
test = new Packages.Test(); test.foo["bar"] = 13; test.foo["baz"] = 14; writeln(test.foo.bar + " " + test.foo.baz + " " + test.foo.fie) for (a in test.foo) { writeln(a + " " + test.foo[a]); }
13 14 null bar 13 baz 14
Statements |  | JS Library
Copyright © 1998-2000 Caucho Technology. All rights reserved. Last modified: Thu, 16 Sep 1999 14:56:49 -0700 (PDT)