[INLONG-9982][Agent] Adjusting the abstraction of source code to facilitate rapid addition of sources

inlong-agent/agent-common/src/main/java/org/apache/inlong/agent/plugin/file/Source.java

@@ -50,6 +50,12 @@ public interface Source {
      */
     void init(InstanceProfile profile);
 
+    /**
+     * Executed after init, usually used to start the source's worker thread
+     *
+     */
+    void start();
+
     /**
      * destroy
      */

inlong-agent/agent-plugins/src/main/java/org/apache/inlong/agent/plugin/sources/DatabaseSqlSource.java

@@ -88,11 +88,41 @@ public List<Reader> split(TaskProfile conf) {
         return readerList;
     }
 
+    @Override
+    protected String getThreadName() {
+        return null;
+    }
+
+    @Override
+    protected void printCurrentState() {
+
+    }
+
+    @Override
+    protected boolean doPrepareToRead() {
+        return false;
+    }
+
+    @Override
+    protected List<SourceData> readFromSource() {
+        return null;
+    }
+
     @Override
     public Message read() {
         return null;
     }
 
+    @Override
+    protected boolean isRunnable() {
+        return runnable;
+    }
+
+    @Override
+    protected void releaseSource() {
+
+    }
+
     @Override
     public boolean sourceFinish() {
         return false;