graalvm js 与java 类型转换的一些方法
在基于跨不同语言的通信开发中，数据类型的转换是一个很大的部分，目前来说graalvm 对于java host 类型与js 对象类似的转换还是不够好
java host 对象到js 的操作我们可以通过ProxyObject 以及提供的HostAccess 注解处理
参考模式
- js 到java 对象转换
这个对应的数据类型还是比较多的，比如普通类型以及java 的pojo 类型
简单类型，graalvm 已经提供了as 方法，但是不是很好的地方是当前不支持直接到pojo，我们需要转换为其他支持的类型再处理,一般我们
日常会使用到的类型有array，string，int，object 。。。。，为了方便我们可以结合 jackson-databind 来处理类型转换
pojo 的我们解决map 类型到pojo 的转换处理
参考代码
Value execResult =result.execute(ProxyObject.fromMap(ob),filed);
Map<String, Object> results = execResult.as(Map.class);
System.out.println("demoappa"+execResult.as(List.class));
ObjectMapper objectMapper = new ObjectMapper();
CollectionType javaType = objectMapper.getTypeFactory()
.constructCollectionType(List.class, MyUser.class);
List myusers = execResult.as(List.class);
System.out.println("myusers"+myusers);
ArrayList<MyUser> users = objectMapper.convertValue(myusers, javaType);
System.out.println("dalong"+users);
Array 类型的转换:
通过Value 提供的as List 转换
Value execResult =result.execute(ProxyObject.fromMap(ob),filed);
Map<String, Object> results = execResult.as(Map.class);
ObjectMapper objectMapper = new ObjectMapper();
CollectionType javaType = objectMapper.getTypeFactory()
.constructCollectionType(List.class, MyUser.class);
List<? extends Object> myusers = execResult.as(List.class);
System.out.println("myusers---"+(List<MyUser>)myusers);
ArrayList<MyUser> users = objectMapper.convertValue(myusers, javaType);
System.out.println("dalong"+users);
目前内部转换的支持代码（后期可能会变）
@TruffleBoundary
private static <T> T asJavaObject(Object value, Class<T> targetType, Type genericType, boolean allowsImplementation, PolyglotLanguageContext languageContext) {
Objects.requireNonNull(value);
InteropLibrary interop = InteropLibrary.getFactory().getUncached(value);
Object obj;
if (interop.isNull(value)) {
if (targetType.isPrimitive()) {
throw HostInteropErrors.nullCoercion(languageContext, value, targetType);
}
return null;
} else if (HostObject.isJavaInstance(targetType, value)) {
obj = HostObject.valueOf(value);
} else if (targetType == Object.class) {
obj = convertToObject(value, languageContext, interop);
} else if (targetType == List.class) {
if (interop.hasArrayElements(value)) {
boolean implementsFunction = shouldImplementFunction(value, interop);
TypeAndClass<?> elementType = getGenericParameterType(genericType, 0);
obj = PolyglotList.create(languageContext, value, implementsFunction, elementType.clazz, elementType.type);
} else {
throw HostInteropErrors.cannotConvert(languageContext, value, targetType, "Value must have array elements.");
}
} else if (targetType == Map.class) {
Class<?> keyClazz = getGenericParameterType(genericType, 0).clazz;
TypeAndClass<?> valueType = getGenericParameterType(genericType, 1);
if (!isSupportedMapKeyType(keyClazz)) {
throw newInvalidKeyTypeException(keyClazz);
}
boolean hasSize = (Number.class.isAssignableFrom(keyClazz)) && interop.hasArrayElements(value);
boolean hasKeys = (keyClazz == Object.class || keyClazz == String.class) && interop.hasMembers(value);
if (hasKeys || hasSize) {
boolean implementsFunction = shouldImplementFunction(value, interop);
obj = PolyglotMap.create(languageContext, value, implementsFunction, keyClazz, valueType.clazz, valueType.type);
} else {
throw HostInteropErrors.cannotConvert(languageContext, value, targetType, "Value must have members or array elements.");
}
} else if (targetType == Function.class) {
TypeAndClass<?> returnType = getGenericParameterType(genericType, 1);
if (interop.isExecutable(value) || interop.isInstantiable(value)) {
obj = PolyglotFunction.create(languageContext, value, returnType.clazz, returnType.type);
} else if (interop.hasMembers(value)) {
obj = HostInteropReflect.newProxyInstance(targetType, value, languageContext);
} else {
throw HostInteropErrors.cannotConvert(languageContext, value, targetType, "Value must be executable or instantiable.");
}
} else if (targetType.isArray()) {
if (interop.hasArrayElements(value)) {
obj = truffleObjectToArray(interop, value, targetType, genericType, languageContext);
} else {
throw HostInteropErrors.cannotConvert(languageContext, value, targetType, "Value must have array elements.");
}
} else if (targetType == LocalDate.class) {
if (interop.isDate(value)) {
try {
obj = interop.asDate(value);
} catch (UnsupportedMessageException e) {
throw shouldNotReachHere(e);
}
} else {
throw HostInteropErrors.cannotConvert(languageContext, value, targetType, "Value must have date and time information.");
}
} else if (targetType == LocalTime.class) {
if (interop.isTime(value)) {
try {
obj = interop.asTime(value);
} catch (UnsupportedMessageException e) {
throw shouldNotReachHere(e);
}
} else {
throw HostInteropErrors.cannotConvert(languageContext, value, targetType, "Value must have date and time information.");
}
} else if (targetType == LocalDateTime.class) {
if (interop.isDate(value) && interop.isTime(value)) {
LocalDate date;
LocalTime time;
try {
date = interop.asDate(value);
time = interop.asTime(value);
} catch (UnsupportedMessageException e) {
throw shouldNotReachHere(e);
}
obj = createDateTime(date, time);
} else {
throw HostInteropErrors.cannotConvert(languageContext, value, targetType, "Value must have date and time information.");
}
} else if (targetType == ZonedDateTime.class) {
if (interop.isDate(value) && interop.isTime(value) && interop.isTimeZone(value)) {
LocalDate date;
LocalTime time;
ZoneId timeZone;
try {
date = interop.asDate(value);
time = interop.asTime(value);
timeZone = interop.asTimeZone(value);
} catch (UnsupportedMessageException e) {
throw shouldNotReachHere(e);
}
obj = createZonedDateTime(date, time, timeZone);
} else {
throw HostInteropErrors.cannotConvert(languageContext, value, targetType, "Value must have date, time and time-zone information.");
}
} else if (targetType == ZoneId.class) {
if (interop.isTimeZone(value)) {
try {
obj = interop.asTimeZone(value);
} catch (UnsupportedMessageException e) {
throw shouldNotReachHere(e);
}
} else {
throw HostInteropErrors.cannotConvert(languageContext, value, targetType, "Value must have time-zone information.");
}
} else if (targetType == Instant.class || targetType == Date.class) {
if (interop.isDate(value) && interop.isTime(value) && interop.isTimeZone(value)) {
Instant instantValue;
try {
instantValue = interop.asInstant(value);
} catch (UnsupportedMessageException e) {
throw shouldNotReachHere(e);
}
if (targetType == Date.class) {
obj = Date.from(instantValue);
} else {
obj = targetType.cast(instantValue);
}
} else {
throw HostInteropErrors.cannotConvert(languageContext, value, targetType, "Value must have date, time and time-zone information.");
}
} else if (targetType == Duration.class) {
if (interop.isDuration(value)) {
try {
obj = interop.asDuration(value);
} catch (UnsupportedMessageException e) {
throw shouldNotReachHere(e);
}
} else {
throw HostInteropErrors.cannotConvert(languageContext, value, targetType, "Value must have duration information.");
}
} else if (targetType == PolyglotException.class) {
if (interop.isException(value)) {
obj = asPolyglotException(value, interop, languageContext);
} else {
throw HostInteropErrors.cannotConvert(languageContext, value, targetType, "Value must be an exception.");
}
} else if (allowsImplementation && targetType.isInterface()) {
if (HostInteropReflect.isFunctionalInterface(targetType) && (interop.isExecutable(value) || interop.isInstantiable(value))) {
obj = HostInteropReflect.asJavaFunction(targetType, value, languageContext);
} else if (interop.hasMembers(value)) {
obj = HostInteropReflect.newProxyInstance(targetType, value, languageContext);
} else {
throw HostInteropErrors.cannotConvert(languageContext, value, targetType, "Value must have members.");
}
} else {
throw HostInteropErrors.cannotConvert(languageContext, value, targetType, "Unsupported target type.");
}
assert targetType.isInstance(obj);
return targetType.cast(obj);
}
- java host object && meethod 2 js
对于object 类型，比较推荐的是通过ProxyObject 进行map转换处理（对应到js 的object）
java 代码:
Map<String, Object> ob =new HashMap<>();
Map<String, Object> ob2 =new HashMap<>();
ob2.put("url","https://plus.google.com/102817283354809142195/posts/F97fqZwJESL");
ob.put("url","https://plus.google.com/102817283354809142195/posts/F97fqZwJESL");
Map<String, Object> ob3 =new HashMap<>();
ob3.put("url","https://plus.google.com/102817283354809142195/posts/F97fqZwJESL");
ob2.put("ob",ProxyObject.fromMap(ob3));
ob.put("id","z12gtjhq3qn2xxl2o224exwiqruvtda0i");
ob.put("object",ProxyObject.fromMap(ob2));
js 代码:
window = this || {}
window.demo = function (datas, fields) {
let mydatas
mydatas = datas;
if (typeof datas === 'string') {
mydatas =JSON.parse(datas)
}
return mask(mydatas, fields)
}
普通java对象通过 @HostAccess 注解暴露
public class Dalong {
@HostAccess.Export
public String username;
@HostAccess.Export
public String password;
@HostAccess.Export
public String token() {
return String.format("%s------%s",this.username,this.password);
}
}
使用
Dalong dalong = new Dalong();
dalong.password="dalong";
dalong.username="dalong";
Context context = Context.newBuilder().allowAllAccess(true).allowHostClassLoading(true).allowHostAccess(hostAccess).allowIO(true).allowNativeAccess(true).engine(engine).build();
context.getBindings("js").putMember("mydalong",dalong);
System.out.println(context.getBindings("js").getMemberKeys());
String myjs = "mydalong.username= \"dalongdemossss\";\n" +
"mydalong.password= \"deeeeeeee\";\n" +
"\n" +
"console.log(\"my token\",mydalong.token())\n" +
"\n";
context.eval("js",myjs);
说明
以上是一些自己简单的整理，实际应该还会有其他更方便的方法,graalvm 的js 能力很强大，很值得使用
参考资料
https://www.graalvm.org/sdk/javadoc/org/graalvm/polyglot/Value.html
https://github.com/AMIS-Services/jfall2019-graalvm/tree/master/polyglot/java2js
https://github.com/graalvm/graaljs/issues/94
