新增 exists 方法判断 count 存在

mybatis-plus-extension/src/main/java/com/baomidou/mybatisplus/extension/conditions/query/ChainQuery.java

@@ -67,6 +67,15 @@ public interface ChainQuery<T> extends ChainWrapper<T> {
         return SqlHelper.retCount(getBaseMapper().selectCount(getWrapper()));
     }
 
+    /**
+     * 判断数据是否存在
+     *
+     * @return true：存在
+     */
+    default boolean exists() {
+        return this.count() > 0;
+    }
+
     /**
      * 获取分页数据
      *

mybatis-plus-extension/src/main/java/com/baomidou/mybatisplus/extension/service/impl/ServiceImpl.java

@@ -65,7 +65,7 @@ public class ServiceImpl<M extends BaseMapper<T>, T> implements IService<T> {
         return entityClass;
     }
 
-    protected Class<T> mapperClass = currentMapperClass();
+    protected Class<M> mapperClass = currentMapperClass();
 
     /**
      * 判断数据库操作是否成功
@@ -79,8 +79,8 @@ public class ServiceImpl<M extends BaseMapper<T>, T> implements IService<T> {
         return SqlHelper.retBool(result);
     }
 
-    protected Class<T> currentMapperClass() {
-        return (Class<T>) ReflectionKit.getSuperClassGenericType(this.getClass(), ServiceImpl.class, 0);
+    protected Class<M> currentMapperClass() {
+        return (Class<M>) ReflectionKit.getSuperClassGenericType(this.getClass(), ServiceImpl.class, 0);
     }
 
     protected Class<T> currentModelClass() {