de.sormuras.javacompilerscriptengine.JavaCompilerScriptEngine Maven / Gradle / Ivy

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package de.sormuras.javacompilerscriptengine;

import java.io.BufferedReader;
import java.io.Reader;
import java.util.stream.Collectors;
import javax.script.AbstractScriptEngine;
import javax.script.Bindings;
import javax.script.Compilable;
import javax.script.CompiledScript;
import javax.script.ScriptContext;
import javax.script.ScriptEngine;
import javax.script.ScriptException;
import javax.script.SimpleBindings;

class JavaCompilerScriptEngine extends AbstractScriptEngine implements Compilable {

  private final JavaCompilerScriptEngineFactory factory;

  JavaCompilerScriptEngine(JavaCompilerScriptEngineFactory factory) {
    this.factory = factory;
    context.setBindings(new SimpleBindings(), ScriptContext.GLOBAL_SCOPE);
    context.setBindings(new SimpleBindings(), ScriptContext.ENGINE_SCOPE);
  }

  @Override
  public Object eval(String script, ScriptContext context) throws ScriptException {
    return compile(script).eval(context);
  }

  @Override
  public Object eval(Reader reader, ScriptContext context) throws ScriptException {
    String script = new BufferedReader(reader).lines().collect(Collectors.joining());
    return eval(script, context);
  }

  @Override
  public Bindings createBindings() {
    return new SimpleBindings();
  }

  @Override
  public JavaCompilerScriptEngineFactory getFactory() {
    return factory;
  }

  @Override
  public CompiledScript compile(String script) throws ScriptException {
    StringBuilder builder = new StringBuilder();
    builder.append("\n");
    builder.append("import javax.script.*;");
    builder.append("\n");
    builder.append("public class CompiledJavaScript extends CompiledScript {\n");
    builder.append("\n");
    builder.append("    private final ScriptEngine engine;\n");
    builder.append("\n");
    builder.append("    public CompiledJavaScript(ScriptEngine engine) {\n");
    builder.append("        this.engine = engine;\n");
    builder.append("    }\n");
    builder.append("\n");
    builder.append("    public Object eval(ScriptContext context) throws ScriptException {\n");
    // TODO Provide helpers around 'context' parameter.
    for (String scriptLine : script.split("\\R")) {
      builder.append("        ");
      builder.append(scriptLine);
    }
    builder.append("    }\n");
    builder.append("\n");
    builder.append("    public ScriptEngine getEngine() {\n");
    builder.append("        return engine;\n");
    builder.append("    }\n");
    builder.append("\n");
    builder.append("}\n");
    try {
      Class evaluatorClass = JavaCompilerUtils.compile("CompiledJavaScript", builder.toString());
      Object evaluatorObject = evaluatorClass.getConstructor(ScriptEngine.class).newInstance(this);
      return (CompiledScript) evaluatorObject;
    } catch (Exception e) {
      throw new ScriptException("Compilation failed for: " + builder + "\n" + e.getMessage());
    }
  }

  @Override
  public CompiledScript compile(Reader reader) throws ScriptException {
    String script = new BufferedReader(reader).lines().collect(Collectors.joining());
    return compile(script);
  }
}