Question

我想通过xtextservlet创建API：

URI：/ xtext-service / parser
在请求正文中输入：＆＃34; Hello Xtext！＆＃34;
API响应：抽象语法树

我使用 Ecslipse DSL工具然后覆盖到 MyDslServlet.xtend 文件：

@WebServlet(name = 'XtextServices', urlPatterns = '/xtext-service/*')
class MyDslServlet extends XtextServlet {
    DisposableRegistry disposableRegistry
    Pattern _pattern2 = Pattern.compile("/parser")
    @Inject
    private ParseHelper<Model> parseHelper

    .....

    override doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        val url =  req.getRequestURL().toString()
        val _matcher = _pattern2.matcher(url)

        if (_matcher.find()) {
            resp.setContentType("text/x-json")

            val myDslParser = new MyDslParser()
            val iParseResult = myDslParser.doParse(text)
            val gson = new Gson()
            gson.toJson(iParseResult.toString(), resp.writer)
        } else {
            val service = getService(req)
            if (!service.hasConflict && (service.hasSideEffects || service.hasTextInput)) {
                // Send error 405 (method not allowed)
                super.doGet(req, resp)
            } else {
                doService(service, resp)
            }
        }
    }
}

但是，总是错误：

[qtp1650967483-11] WARN org.eclipse.jetty.servlet.ServletHandler - /xtext-service/parser
java.lang.NullPointerException
    at org.eclipse.xtext.parser.antlr.AbstractAntlrParser.parse(AbstractAntlrParser.java:84)
    at org.eclipse.xtext.parser.antlr.AbstractAntlrParser.doParse(AbstractAntlrParser.java:62)
    at org.eclipse.xtext.parser.antlr.AbstractAntlrParser.doParse(AbstractAntlrParser.java:70)
    at org.xtext.example.mydsl.web.MyDslServlet.doGet(MyDslServlet.java:72)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:687)
    at

Xtext从servlet获取AST

0 个答案: