Add VersionManager::findCurrentVersion

src/main/java/io/github/gitbucket/solidbase/manager/JDBCVersionManager.java

@@ -5,6 +5,7 @@
 
 import java.sql.Connection;
 import java.sql.ResultSet;
+import java.util.Optional;
 
 /**
  * Created by takezoe on 15/11/23.
@@ -37,6 +38,15 @@ public String getCurrentVersion(String moduleId) throws Exception {
         return selectStringFromDatabase(conn, "SELECT VERSION FROM VERSIONS WHERE MODULE_ID = ?", moduleId);
     }
 
+    @Override
+    public Optional<String> findCurrentVersion(String moduleId) throws Exception {
+        if (!checkTableExist()) {
+            return Optional.empty();
+        } else {
+            return Optional.ofNullable(getCurrentVersion(moduleId));
+        }
+    }
+
     protected boolean checkTableExist(){
         try {
             ResultSet rs = conn.getMetaData().getTables(null, null, "%", new String[]{ "TABLE" });

src/main/java/io/github/gitbucket/solidbase/manager/VersionManager.java

@@ -1,5 +1,7 @@
 package io.github.gitbucket.solidbase.manager;
 
+import java.util.Optional;
+
 public interface VersionManager {
 
     void initialize() throws Exception;
@@ -8,4 +10,6 @@ public interface VersionManager {
 
     String getCurrentVersion(String moduleId) throws Exception;
 
+    Optional<String> findCurrentVersion(String moduleId) throws Exception;
+
 }

src/test/java/io/github/gitbucket/solidbase/manager/JDBCVersionManagerTest.java

@@ -0,0 +1,40 @@
+package io.github.gitbucket.solidbase.manager;
+
+import org.junit.Test;
+
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.util.Optional;
+
+import static org.junit.Assert.*;
+
+public class JDBCVersionManagerTest {
+
+    @Test(expected = Exception.class)
+    public void testGetCurrentVersionThrowsWhenVersionsTableIsMissing() throws Exception {
+        try (Connection conn = DriverManager.getConnection("jdbc:h2:mem:test-getCurrentVersion-missing-table", "sa", "sa")) {
+            JDBCVersionManager manager = new JDBCVersionManager(conn);
+            manager.getCurrentVersion("test");
+        }
+    }
+
+    @Test
+    public void testFindCurrentVersionIsEmptyWhenVersionsTableIsMissing() throws Exception {
+        try (Connection conn = DriverManager.getConnection("jdbc:h2:mem:test-findCurrentVersion-missing-table", "sa", "sa")) {
+            JDBCVersionManager manager = new JDBCVersionManager(conn);
+
+            assertEquals(Optional.empty(), manager.findCurrentVersion("test"));
+        }
+    }
+
+    @Test
+    public void testFindCurrentVersionReturnsVersionWhenVersionsTableIsPresent() throws Exception {
+        try (Connection conn = DriverManager.getConnection("jdbc:h2:mem:test-findCurrentVersion-present-table", "sa", "sa")) {
+            JDBCVersionManager manager = new JDBCVersionManager(conn);
+            manager.initialize();
+            manager.updateVersion("test", "1.0.0");
+
+            assertEquals(Optional.of("1.0.0"), manager.findCurrentVersion("test"));
+        }
+    }
+}