diff --git a/src/main/java/ru/ulstu/extractor/heuristic/api/StructuralUnitIdentifier.java b/src/main/java/ru/ulstu/extractor/heuristic/api/StructuralUnitIdentifier.java
new file mode 100644
index 0000000..3ba09e6
--- /dev/null
+++ b/src/main/java/ru/ulstu/extractor/heuristic/api/StructuralUnitIdentifier.java
@@ -0,0 +1,23 @@
+package ru.ulstu.extractor.heuristic.api;
+
+import ru.ulstu.extractor.heuristic.model.BuildTool;
+import ru.ulstu.extractor.heuristic.model.ProgrammingLanguage;
+import ru.ulstu.extractor.heuristic.model.StructuralUnit;
+
+import java.util.List;
+
+public interface StructuralUnitIdentifier {
+    List<StructuralUnit> getEntityClasses();
+
+    List<StructuralUnit> getBusinessLogicClasses();
+
+    ProgrammingLanguage getMainProgrammingLanguage();
+
+    boolean isMultiModuleProject();
+
+    BuildTool getBuildTool();
+
+    default boolean canAppliedToProject() {
+        return false;
+    }
+}
diff --git a/src/main/java/ru/ulstu/extractor/heuristic/model/BuildTool.java b/src/main/java/ru/ulstu/extractor/heuristic/model/BuildTool.java
new file mode 100644
index 0000000..e6e9a6f
--- /dev/null
+++ b/src/main/java/ru/ulstu/extractor/heuristic/model/BuildTool.java
@@ -0,0 +1,16 @@
+package ru.ulstu.extractor.heuristic.model;
+
+public abstract class BuildTool {
+    private final String name;
+
+    public BuildTool(String name) {
+        this.name = name;
+    }
+
+    protected abstract boolean canAppliedToProject();
+
+    public String getName() {
+        return name;
+    }
+
+}
diff --git a/src/main/java/ru/ulstu/extractor/heuristic/model/GradleBuildTool.java b/src/main/java/ru/ulstu/extractor/heuristic/model/GradleBuildTool.java
new file mode 100644
index 0000000..c99c245
--- /dev/null
+++ b/src/main/java/ru/ulstu/extractor/heuristic/model/GradleBuildTool.java
@@ -0,0 +1,13 @@
+package ru.ulstu.extractor.heuristic.model;
+
+public class GradleBuildTool extends BuildTool {
+
+    public GradleBuildTool() {
+        super("Gradle");
+    }
+
+    @Override
+    protected boolean canAppliedToProject() {
+        return false;
+    }
+}
diff --git a/src/main/java/ru/ulstu/extractor/heuristic/model/JavaProgrammingLanguage.java b/src/main/java/ru/ulstu/extractor/heuristic/model/JavaProgrammingLanguage.java
new file mode 100644
index 0000000..867328c
--- /dev/null
+++ b/src/main/java/ru/ulstu/extractor/heuristic/model/JavaProgrammingLanguage.java
@@ -0,0 +1,7 @@
+package ru.ulstu.extractor.heuristic.model;
+
+public class JavaProgrammingLanguage extends ProgrammingLanguage {
+    public JavaProgrammingLanguage() {
+        super("Java");
+    }
+}
diff --git a/src/main/java/ru/ulstu/extractor/heuristic/model/ProgrammingLanguage.java b/src/main/java/ru/ulstu/extractor/heuristic/model/ProgrammingLanguage.java
new file mode 100644
index 0000000..a872270
--- /dev/null
+++ b/src/main/java/ru/ulstu/extractor/heuristic/model/ProgrammingLanguage.java
@@ -0,0 +1,13 @@
+package ru.ulstu.extractor.heuristic.model;
+
+public abstract class ProgrammingLanguage {
+    private final String name;
+
+    public ProgrammingLanguage(String name) {
+        this.name = name;
+    }
+
+    public String getName() {
+        return name;
+    }
+}
diff --git a/src/main/java/ru/ulstu/extractor/heuristic/model/StructuralUnit.java b/src/main/java/ru/ulstu/extractor/heuristic/model/StructuralUnit.java
new file mode 100644
index 0000000..64ce9b2
--- /dev/null
+++ b/src/main/java/ru/ulstu/extractor/heuristic/model/StructuralUnit.java
@@ -0,0 +1,14 @@
+package ru.ulstu.extractor.heuristic.model;
+
+public abstract class StructuralUnit {
+    private String pathToFile;
+    private String moduleName;
+
+    public String getPathToFile() {
+        return pathToFile;
+    }
+
+    public String getModuleName() {
+        return moduleName;
+    }
+}
diff --git a/src/main/java/ru/ulstu/extractor/heuristic/service/JavaIdentifier.java b/src/main/java/ru/ulstu/extractor/heuristic/service/JavaIdentifier.java
new file mode 100644
index 0000000..98c7283
--- /dev/null
+++ b/src/main/java/ru/ulstu/extractor/heuristic/service/JavaIdentifier.java
@@ -0,0 +1,45 @@
+package ru.ulstu.extractor.heuristic.service;
+
+import org.springframework.stereotype.Service;
+import ru.ulstu.extractor.heuristic.api.StructuralUnitIdentifier;
+import ru.ulstu.extractor.heuristic.model.BuildTool;
+import ru.ulstu.extractor.heuristic.model.GradleBuildTool;
+import ru.ulstu.extractor.heuristic.model.JavaProgrammingLanguage;
+import ru.ulstu.extractor.heuristic.model.ProgrammingLanguage;
+import ru.ulstu.extractor.heuristic.model.StructuralUnit;
+
+import java.util.List;
+
+@Service
+public class JavaIdentifier implements StructuralUnitIdentifier {
+    @Override
+    public boolean canAppliedToProject() {
+        return getBuildTool() instanceof GradleBuildTool
+                && getMainProgrammingLanguage() instanceof JavaProgrammingLanguage;
+    }
+
+    @Override
+    public List<StructuralUnit> getEntityClasses() {
+        return null;
+    }
+
+    @Override
+    public List<StructuralUnit> getBusinessLogicClasses() {
+        return null;
+    }
+
+    @Override
+    public ProgrammingLanguage getMainProgrammingLanguage() {
+        return null;
+    }
+
+    @Override
+    public boolean isMultiModuleProject() {
+        return false;
+    }
+
+    @Override
+    public BuildTool getBuildTool() {
+        return null;
+    }
+}
diff --git a/src/main/java/ru/ulstu/extractor/heuristic/service/StructuralUnitService.java b/src/main/java/ru/ulstu/extractor/heuristic/service/StructuralUnitService.java
new file mode 100644
index 0000000..7cbf8dd
--- /dev/null
+++ b/src/main/java/ru/ulstu/extractor/heuristic/service/StructuralUnitService.java
@@ -0,0 +1,24 @@
+package ru.ulstu.extractor.heuristic.service;
+
+import org.springframework.stereotype.Service;
+import ru.ulstu.extractor.heuristic.api.StructuralUnitIdentifier;
+import ru.ulstu.extractor.heuristic.model.StructuralUnit;
+
+import java.util.List;
+
+@Service
+public class StructuralUnitService {
+    private final List<StructuralUnitIdentifier> structuralUnitIdentifiers;
+
+    public StructuralUnitService(List<StructuralUnitIdentifier> structuralUnitIdentifiers) {
+        this.structuralUnitIdentifiers = structuralUnitIdentifiers;
+    }
+
+    public List<StructuralUnit> getEntities() {
+        StructuralUnitIdentifier selectedIdentifier = structuralUnitIdentifiers.stream()
+                .filter(StructuralUnitIdentifier::canAppliedToProject)
+                .findAny()
+                .orElseThrow(() -> new RuntimeException("Identifier not found"));
+        return selectedIdentifier.getEntityClasses();
+    }
+}