java - 如何使用 ParseHelper 从 DSL 解析到 Object
问题描述
我想用 ParseHelper 解析一个写入 JsonObject 的 DSL 程序
public static JsonModel toJsonModel(CharSequence c) {
ParseHelper<JsonModel> parseHelper = new ParseHelper<JsonModel>();
try {
return parseHelper.parse(c);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
public static void main(String args[]) {
String chaine = "jsonValue { \"Nom\" : \"Toto\",\r\n"
+ " \"Adresse\" : { \r\n"
+ " \"Adresse 1\" : \"x avenue de xx\",\r\n"
+ " \"Adresse 2\" : \" x rue de xx\"\r\n"
+ " },\r\n"
+ " }\r\n"
+ " filename = \"jsonFileToRead.json\"\r\n"
+ " SearchForKey(\"xx\") in jsonValue\r\n";
CharSequence c = "'''"+chaine+"'''";
JsonModel model = toJsonModel(c);
}
但我似乎无法解析,我收到以下错误:
java.lang.NullPointerException: Cannot invoke "org.eclipse.xtext.testing.util.ResourceHelper.createResourceSet()" because "this.resourceHelper" is null
at org.eclipse.xtext.testing.util.ParseHelper.parse(ParseHelper.java:65)
at org.istic.idm.tests.TempsMemoire.toJsonModel(TempsMemoire.java:14)
at org.istic.idm.tests.TempsMemoire.main(TempsMemoire.java:49)
解决方案
您需要使用注入来获取 parsehelper,例如
import org.eclipse.xtext.testing.util.ParseHelper;
import org.xtext.example.mydsl5.MyDslStandaloneSetup;
import org.xtext.example.mydsl5.myDsl.Model;
import com.google.inject.Inject;
import com.google.inject.Injector;
public class Main {
public static void main(String[] args) throws Exception {
Injector injector = new MyDslStandaloneSetup().createInjectorAndDoEMFRegistration();
Main main = injector.getInstance(Main.class);
System.out.println(main.doGetModel("Hello World!"));
}
@Inject ParseHelper<Model> parserHelper;
public Model doGetModel(String content) throws Exception {
return parserHelper.parse(content);
}
}
或者
import org.eclipse.xtext.testing.util.ParseHelper;
import org.xtext.example.mydsl5.MyDslStandaloneSetup;
import org.xtext.example.mydsl5.myDsl.Model;
import com.google.inject.Injector;
import com.google.inject.Key;
import com.google.inject.TypeLiteral;
public class Main {
public static void main(String[] args) throws Exception {
System.out.println(doGetModel("Hello World!"));
}
public static Model doGetModel(String content) throws Exception {
Injector injector = new MyDslStandaloneSetup().createInjectorAndDoEMFRegistration();
ParseHelper<Model> parserHelper = injector.getInstance(Key.get(new TypeLiteral<ParseHelper<Model>>() {}));
return parserHelper.parse(content);
}
}
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