新增查询 boolean 的方法，并简单重构代码。

src/main/java/xyz/zhouxy/jdbc/JdbcOperationSupport.java

@@ -26,10 +26,6 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
-import java.util.Optional;
-import java.util.OptionalDouble;
-import java.util.OptionalInt;
-import java.util.OptionalLong;
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
@@ -38,7 +34,6 @@ import com.google.common.collect.Lists;
 
 import xyz.zhouxy.plusone.commons.collection.CollectionTools;
 import xyz.zhouxy.plusone.commons.util.AssertTools;
-import xyz.zhouxy.plusone.commons.util.OptionalTools;
 
 /**
  * JdbcOperationSupport
@@ -111,14 +106,14 @@ class JdbcOperationSupport {
     // #region - queryFirst
 
     /**
-     * 执行查询，将查询结果的第一行数据按照指定逻辑进行处理，返回 {@link Optional}
+     * 执行查询，将查询结果的第一行数据按照指定逻辑进行映射
      *
      * @param conn      数据库连接
      * @param sql       SQL
      * @param params    参数
      * @param rowMapper {@link ResultSet} 中每一行的数据的处理逻辑
      */
-    static <T> Optional<T> queryFirst(Connection conn, String sql, Object[] params, RowMapper<T> rowMapper)
+    static <T> T queryFirst(Connection conn, String sql, Object[] params, RowMapper<T> rowMapper)
             throws SQLException {
         assertConnectionNotNull(conn);
         assertSqlNotNull(sql);
@@ -134,7 +129,7 @@ class JdbcOperationSupport {
      * @param params 参数
      * @param clazz  目标类型
      */
-    static <T> Optional<T> queryFirst(Connection conn, String sql, Object[] params, Class<T> clazz)
+    static <T> T queryFirst(Connection conn, String sql, Object[] params, Class<T> clazz)
             throws SQLException {
         assertConnectionNotNull(conn);
         assertSqlNotNull(sql);
@@ -149,7 +144,7 @@ class JdbcOperationSupport {
      * @param sql    SQL
      * @param params 参数
      */
-    static Optional<String> queryFirstString(Connection conn, String sql, Object[] params)
+    static String queryFirstString(Connection conn, String sql, Object[] params)
             throws SQLException {
         return queryFirst(conn, sql, params, (rs, rowNumber) -> rs.getString(1));
     }
@@ -161,10 +156,9 @@ class JdbcOperationSupport {
      * @param sql    SQL
      * @param params 参数
      */
-    static OptionalInt queryFirstInt(Connection conn, String sql, Object[] params)
+    static Integer queryFirstInt(Connection conn, String sql, Object[] params)
             throws SQLException {
-        Optional<Integer> result = queryFirst(conn, sql, params, (rs, rowNumber) -> rs.getInt(1));
-        return OptionalTools.toOptionalInt(result);
+        return queryFirst(conn, sql, params, (rs, rowNumber) -> rs.getInt(1));
     }
 
     /**
@@ -174,10 +168,9 @@ class JdbcOperationSupport {
      * @param sql    SQL
      * @param params 参数
      */
-    static OptionalLong queryFirstLong(Connection conn, String sql, Object[] params)
+    static Long queryFirstLong(Connection conn, String sql, Object[] params)
             throws SQLException {
-        Optional<Long> result = queryFirst(conn, sql, params, (rs, rowNumber) -> rs.getLong(1));
-        return OptionalTools.toOptionalLong(result);
+        return queryFirst(conn, sql, params, (rs, rowNumber) -> rs.getLong(1));
     }
 
     /**
@@ -187,10 +180,9 @@ class JdbcOperationSupport {
      * @param sql    SQL
      * @param params 参数
      */
-    static OptionalDouble queryFirstDouble(Connection conn, String sql, Object[] params)
+    static Double queryFirstDouble(Connection conn, String sql, Object[] params)
             throws SQLException {
-        Optional<Double> result = queryFirst(conn, sql, params, (rs, rowNumber) -> rs.getDouble(1));
-        return OptionalTools.toOptionalDouble(result);
+        return queryFirst(conn, sql, params, (rs, rowNumber) -> rs.getDouble(1));
     }
 
     /**
@@ -200,11 +192,23 @@ class JdbcOperationSupport {
      * @param sql    SQL
      * @param params 参数
      */
-    static Optional<BigDecimal> queryFirstBigDecimal(Connection conn, String sql, Object[] params)
+    static BigDecimal queryFirstBigDecimal(Connection conn, String sql, Object[] params)
             throws SQLException {
         return queryFirst(conn, sql, params, (rs, rowNumber) -> rs.getBigDecimal(1));
     }
 
+    /**
+     * 查询结果，并转换为 bool 值
+     *
+     * @param conn   数据库连接
+     * @param sql    SQL
+     * @param params 参数
+     */
+    static Boolean queryFirstBoolean(Connection conn, String sql, Object[] params)
+            throws SQLException {
+        return queryFirst(conn, sql, params, (rs, rowNumber) -> rs.getBoolean(1));
+    }
+
     // #endregion
 
     // #region - update & batchUpdate
@@ -357,9 +361,9 @@ class JdbcOperationSupport {
      * @param resultHandler 结果处理器，用于处理 {@link ResultSet}
      */
     private static <T> T queryInternal(@Nonnull Connection conn,
-                                        @Nonnull String sql,
-                                        @Nullable Object[] params,
-                                        @Nonnull ResultHandler<T> resultHandler)
+                                       @Nonnull String sql,
+                                       @Nullable Object[] params,
+                                       @Nonnull ResultHandler<T> resultHandler)
             throws SQLException {
         try (PreparedStatement stmt = conn.prepareStatement(sql)) {
             fillStatement(stmt, params);
@@ -378,9 +382,9 @@ class JdbcOperationSupport {
      * @param rowMapper {@link ResultSet} 中每一行的数据的处理逻辑
      */
     private static <T> List<T> queryListInternal(@Nonnull Connection conn,
-                                            @Nonnull String sql,
-                                            @Nullable Object[] params,
-                                            @Nonnull RowMapper<T> rowMapper)
+                                                 @Nonnull String sql,
+                                                 @Nullable Object[] params,
+                                                 @Nonnull RowMapper<T> rowMapper)
             throws SQLException {
         return queryInternal(conn, sql, params, rs -> {
             List<T> result = new ArrayList<>();
@@ -401,17 +405,13 @@ class JdbcOperationSupport {
      * @param params    参数
      * @param rowMapper 行数据映射逻辑
      */
-    private static <T> Optional<T> queryFirstInternal(@Nonnull Connection conn,
+    private static <T> T queryFirstInternal(@Nonnull Connection conn,
                                             @Nonnull String sql,
                                             @Nullable Object[] params,
                                             @Nonnull RowMapper<T> rowMapper)
             throws SQLException {
-        return queryInternal(conn, sql, params, rs -> {
-            if (rs.next()) {
-                return Optional.ofNullable(rowMapper.mapRow(rs, 0));
-            }
-            return Optional.empty();
-        });
+        return queryInternal(conn, sql, params, rs ->
+                rs.next() ? rowMapper.mapRow(rs, 0) : null);
     }
 
     // #endregion

src/main/java/xyz/zhouxy/jdbc/JdbcOperations.java

@@ -285,6 +285,22 @@ interface JdbcOperations {
     Optional<BigDecimal> queryFirstBigDecimal(String sql)
             throws SQLException;
 
+    /**
+     * 查询结果，并转换为 boolean
+     *
+     * @param sql SQL
+     */
+    boolean queryAsBoolean(String sql)
+            throws SQLException;
+
+    /**
+     * 查询结果，并转换为 boolean
+     *
+     * @param sql SQL
+     */
+    boolean queryAsBoolean(String sql, Object[] params)
+            throws SQLException;
+
     // #endregion
 
     // #region - update & batchUpdate

src/main/java/xyz/zhouxy/jdbc/SimpleJdbcTemplate.java

@@ -34,6 +34,7 @@ import javax.sql.DataSource;
 import xyz.zhouxy.plusone.commons.function.ThrowingConsumer;
 import xyz.zhouxy.plusone.commons.function.ThrowingPredicate;
 import xyz.zhouxy.plusone.commons.util.AssertTools;
+import xyz.zhouxy.plusone.commons.util.OptionalTools;
 
 /**
  * SimpleJdbcTemplate
@@ -138,7 +139,8 @@ public class SimpleJdbcTemplate implements JdbcOperations {
     public List<Map<String, Object>> queryList(String sql)
             throws SQLException {
         try (Connection conn = this.dataSource.getConnection()) {
-            return JdbcOperationSupport.queryList(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, RowMapper.HASH_MAP_MAPPER);
+            return JdbcOperationSupport
+                    .queryList(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, RowMapper.HASH_MAP_MAPPER);
         }
     }
 
@@ -147,7 +149,8 @@ public class SimpleJdbcTemplate implements JdbcOperations {
     public List<DbRecord> queryRecordList(String sql)
             throws SQLException {
         try (Connection conn = this.dataSource.getConnection()) {
-            return JdbcOperationSupport.queryList(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, RowMapper.RECORD_MAPPER);
+            return JdbcOperationSupport
+                    .queryList(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, RowMapper.RECORD_MAPPER);
         }
     }
 
@@ -160,7 +163,8 @@ public class SimpleJdbcTemplate implements JdbcOperations {
     public <T> Optional<T> queryFirst(String sql, Object[] params, RowMapper<T> rowMapper)
             throws SQLException {
         try (Connection conn = this.dataSource.getConnection()) {
-            return JdbcOperationSupport.queryFirst(conn, sql, params, rowMapper);
+            final T result = JdbcOperationSupport.queryFirst(conn, sql, params, rowMapper);
+            return Optional.ofNullable(result);
         }
     }
 
@@ -169,7 +173,8 @@ public class SimpleJdbcTemplate implements JdbcOperations {
     public <T> Optional<T> queryFirst(String sql, Object[] params, Class<T> clazz)
             throws SQLException {
         try (Connection conn = this.dataSource.getConnection()) {
-            return JdbcOperationSupport.queryFirst(conn, sql, params, clazz);
+            final T result = JdbcOperationSupport.queryFirst(conn, sql, params, clazz);
+            return Optional.ofNullable(result);
         }
     }
 
@@ -178,7 +183,9 @@ public class SimpleJdbcTemplate implements JdbcOperations {
     public Optional<Map<String, Object>> queryFirst(String sql, Object[] params)
             throws SQLException {
         try (Connection conn = this.dataSource.getConnection()) {
-            return JdbcOperationSupport.queryFirst(conn, sql, params, RowMapper.HASH_MAP_MAPPER);
+            final Map<String, Object> result = JdbcOperationSupport
+                    .queryFirst(conn, sql, params, RowMapper.HASH_MAP_MAPPER);
+            return Optional.ofNullable(result);
         }
     }
 
@@ -187,7 +194,9 @@ public class SimpleJdbcTemplate implements JdbcOperations {
     public Optional<DbRecord> queryFirstRecord(String sql, Object[] params)
             throws SQLException {
         try (Connection conn = this.dataSource.getConnection()) {
-            return JdbcOperationSupport.queryFirst(conn, sql, params, RowMapper.RECORD_MAPPER);
+            final DbRecord result = JdbcOperationSupport
+                    .queryFirst(conn, sql, params, RowMapper.RECORD_MAPPER);
+            return Optional.ofNullable(result);
         }
     }
 
@@ -196,7 +205,8 @@ public class SimpleJdbcTemplate implements JdbcOperations {
     public Optional<String> queryFirstString(String sql, Object[] params)
             throws SQLException {
         try (Connection conn = this.dataSource.getConnection()) {
-            return JdbcOperationSupport.queryFirstString(conn, sql, params);
+            final String result = JdbcOperationSupport.queryFirstString(conn, sql, params);
+            return Optional.ofNullable(result);
         }
     }
 
@@ -205,7 +215,8 @@ public class SimpleJdbcTemplate implements JdbcOperations {
     public OptionalInt queryFirstInt(String sql, Object[] params)
             throws SQLException {
         try (Connection conn = this.dataSource.getConnection()) {
-            return JdbcOperationSupport.queryFirstInt(conn, sql, params);
+            final Integer result = JdbcOperationSupport.queryFirstInt(conn, sql, params);
+            return OptionalTools.optionalOf(result);
         }
     }
 
@@ -214,7 +225,8 @@ public class SimpleJdbcTemplate implements JdbcOperations {
     public OptionalLong queryFirstLong(String sql, Object[] params)
             throws SQLException {
         try (Connection conn = this.dataSource.getConnection()) {
-            return JdbcOperationSupport.queryFirstLong(conn, sql, params);
+            final Long result = JdbcOperationSupport.queryFirstLong(conn, sql, params);
+            return OptionalTools.optionalOf(result);
         }
     }
 
@@ -223,7 +235,8 @@ public class SimpleJdbcTemplate implements JdbcOperations {
     public OptionalDouble queryFirstDouble(String sql, Object[] params)
             throws SQLException {
         try (Connection conn = this.dataSource.getConnection()) {
-            return JdbcOperationSupport.queryFirstDouble(conn, sql, params);
+            final Double result = JdbcOperationSupport.queryFirstDouble(conn, sql, params);
+            return OptionalTools.optionalOf(result);
         }
     }
 
@@ -232,7 +245,8 @@ public class SimpleJdbcTemplate implements JdbcOperations {
     public Optional<BigDecimal> queryFirstBigDecimal(String sql, Object[] params)
             throws SQLException {
         try (Connection conn = this.dataSource.getConnection()) {
-            return JdbcOperationSupport.queryFirstBigDecimal(conn, sql, params);
+            final BigDecimal result = JdbcOperationSupport.queryFirstBigDecimal(conn, sql, params);
+            return Optional.ofNullable(result);
         }
     }
 
@@ -241,7 +255,9 @@ public class SimpleJdbcTemplate implements JdbcOperations {
     public <T> Optional<T> queryFirst(String sql, RowMapper<T> rowMapper)
             throws SQLException {
         try (Connection conn = this.dataSource.getConnection()) {
-            return JdbcOperationSupport.queryFirst(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, rowMapper);
+            final T result = JdbcOperationSupport
+                    .queryFirst(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, rowMapper);
+            return Optional.ofNullable(result);
         }
     }
 
@@ -250,7 +266,9 @@ public class SimpleJdbcTemplate implements JdbcOperations {
     public <T> Optional<T> queryFirst(String sql, Class<T> clazz)
             throws SQLException {
         try (Connection conn = this.dataSource.getConnection()) {
-            return JdbcOperationSupport.queryFirst(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, clazz);
+            final T result = JdbcOperationSupport
+                    .queryFirst(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, clazz);
+            return Optional.ofNullable(result);
         }
     }
 
@@ -259,7 +277,9 @@ public class SimpleJdbcTemplate implements JdbcOperations {
     public Optional<Map<String, Object>> queryFirst(String sql)
             throws SQLException {
         try (Connection conn = this.dataSource.getConnection()) {
-            return JdbcOperationSupport.queryFirst(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, RowMapper.HASH_MAP_MAPPER);
+            final Map<String, Object> result = JdbcOperationSupport
+                    .queryFirst(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, RowMapper.HASH_MAP_MAPPER);
+            return Optional.ofNullable(result);
         }
     }
 
@@ -268,7 +288,9 @@ public class SimpleJdbcTemplate implements JdbcOperations {
     public Optional<DbRecord> queryFirstRecord(String sql)
             throws SQLException {
         try (Connection conn = this.dataSource.getConnection()) {
-            return JdbcOperationSupport.queryFirst(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, RowMapper.RECORD_MAPPER);
+            final DbRecord result = JdbcOperationSupport
+                    .queryFirst(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, RowMapper.RECORD_MAPPER);
+            return Optional.ofNullable(result);
         }
     }
 
@@ -277,7 +299,9 @@ public class SimpleJdbcTemplate implements JdbcOperations {
     public Optional<String> queryFirstString(String sql)
             throws SQLException {
         try (Connection conn = this.dataSource.getConnection()) {
-            return JdbcOperationSupport.queryFirstString(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            final String result = JdbcOperationSupport.
+                    queryFirstString(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            return Optional.ofNullable(result);
         }
     }
 
@@ -286,7 +310,9 @@ public class SimpleJdbcTemplate implements JdbcOperations {
     public OptionalInt queryFirstInt(String sql)
             throws SQLException {
         try (Connection conn = this.dataSource.getConnection()) {
-            return JdbcOperationSupport.queryFirstInt(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            final Integer result = JdbcOperationSupport
+                    .queryFirstInt(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            return OptionalTools.optionalOf(result);
         }
     }
 
@@ -295,7 +321,9 @@ public class SimpleJdbcTemplate implements JdbcOperations {
     public OptionalLong queryFirstLong(String sql)
             throws SQLException {
         try (Connection conn = this.dataSource.getConnection()) {
-            return JdbcOperationSupport.queryFirstLong(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            final Long result = JdbcOperationSupport
+                    .queryFirstLong(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            return OptionalTools.optionalOf(result);
         }
     }
 
@@ -304,7 +332,9 @@ public class SimpleJdbcTemplate implements JdbcOperations {
     public OptionalDouble queryFirstDouble(String sql)
             throws SQLException {
         try (Connection conn = this.dataSource.getConnection()) {
-            return JdbcOperationSupport.queryFirstDouble(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            final Double result = JdbcOperationSupport
+                    .queryFirstDouble(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            return OptionalTools.optionalOf(result);
         }
     }
 
@@ -313,7 +343,31 @@ public class SimpleJdbcTemplate implements JdbcOperations {
     public Optional<BigDecimal> queryFirstBigDecimal(String sql)
             throws SQLException {
         try (Connection conn = this.dataSource.getConnection()) {
-            return JdbcOperationSupport.queryFirstBigDecimal(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            final BigDecimal result = JdbcOperationSupport
+                    .queryFirstBigDecimal(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            return Optional.ofNullable(result);
+        }
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public boolean queryAsBoolean(String sql) // TODO 单元测试
+            throws SQLException {
+        try (Connection conn = this.dataSource.getConnection()) {
+            final Boolean result = JdbcOperationSupport
+                    .queryFirstBoolean(conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            return Boolean.TRUE.equals(result);
+        }
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public boolean queryAsBoolean(String sql, Object[] params) // TODO 单元测试
+            throws SQLException {
+        try (Connection conn = this.dataSource.getConnection()) {
+            final Boolean result = JdbcOperationSupport
+                    .queryFirstBoolean(conn, sql, params);
+            return Boolean.TRUE.equals(result);
         }
     }
 
@@ -372,7 +426,8 @@ public class SimpleJdbcTemplate implements JdbcOperations {
             int batchSize, List<Exception> exceptions)
             throws SQLException {
         try (Connection conn = this.dataSource.getConnection()) {
-            return JdbcOperationSupport.batchUpdateAndIgnoreException(conn, sql, params, batchSize, exceptions);
+            return JdbcOperationSupport
+                    .batchUpdateAndIgnoreException(conn, sql, params, batchSize, exceptions);
         }
     }
 
@@ -392,7 +447,8 @@ public class SimpleJdbcTemplate implements JdbcOperations {
      * @throws SQLException SQL 异常
      * @throws E            事务中的异常
      */
-    public <E extends Exception> void executeTransaction(@Nonnull final ThrowingConsumer<JdbcExecutor, E> operations)
+    public <E extends Exception> void executeTransaction(
+            @Nonnull final ThrowingConsumer<JdbcExecutor, E> operations)
             throws SQLException, E {
         AssertTools.checkNotNull(operations, "Operations can not be null.");
         try (Connection conn = this.dataSource.getConnection()) {
@@ -422,7 +478,8 @@ public class SimpleJdbcTemplate implements JdbcOperations {
      * @throws SQLException 数据库异常
      * @throws E            事务中的异常类型
      */
-    public <E extends Exception> void commitIfTrue(@Nonnull final ThrowingPredicate<JdbcExecutor, E> operations)
+    public <E extends Exception> void commitIfTrue(
+            @Nonnull final ThrowingPredicate<JdbcExecutor, E> operations)
             throws SQLException, E {
         AssertTools.checkNotNull(operations, "Operations can not be null.");
         try (Connection conn = this.dataSource.getConnection()) {
@@ -469,7 +526,8 @@ public class SimpleJdbcTemplate implements JdbcOperations {
         @Override
         public <T> T query(String sql, ResultHandler<T> resultHandler)
                 throws SQLException {
-            return JdbcOperationSupport.query(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, resultHandler);
+            return JdbcOperationSupport
+                    .query(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, resultHandler);
         }
 
         // #endregion
@@ -508,7 +566,8 @@ public class SimpleJdbcTemplate implements JdbcOperations {
         @Override
         public <T> List<T> queryList(String sql, RowMapper<T> rowMapper)
                 throws SQLException {
-            return JdbcOperationSupport.queryList(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, rowMapper);
+            return JdbcOperationSupport
+                    .queryList(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, rowMapper);
         }
 
         /** {@inheritDoc} */
@@ -522,14 +581,16 @@ public class SimpleJdbcTemplate implements JdbcOperations {
         @Override
         public List<Map<String, Object>> queryList(String sql)
                 throws SQLException {
-            return JdbcOperationSupport.queryList(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, RowMapper.HASH_MAP_MAPPER);
+            return JdbcOperationSupport
+                    .queryList(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, RowMapper.HASH_MAP_MAPPER);
         }
 
         /** {@inheritDoc} */
         @Override
         public List<DbRecord> queryRecordList(String sql)
                 throws SQLException {
-            return JdbcOperationSupport.queryList(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, RowMapper.RECORD_MAPPER);
+            return JdbcOperationSupport
+                    .queryList(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, RowMapper.RECORD_MAPPER);
         }
 
         // #endregion
@@ -540,126 +601,172 @@ public class SimpleJdbcTemplate implements JdbcOperations {
         @Override
         public <T> Optional<T> queryFirst(String sql, Object[] params, RowMapper<T> rowMapper)
                 throws SQLException {
-            return JdbcOperationSupport.queryFirst(this.conn, sql, params, rowMapper);
+            final T result = JdbcOperationSupport.queryFirst(this.conn, sql, params, rowMapper);
+            return Optional.ofNullable(result);
         }
 
         /** {@inheritDoc} */
         @Override
         public <T> Optional<T> queryFirst(String sql, Object[] params, Class<T> clazz)
                 throws SQLException {
-            return JdbcOperationSupport.queryFirst(this.conn, sql, params, clazz);
+            final T result = JdbcOperationSupport.queryFirst(this.conn, sql, params, clazz);
+            return Optional.ofNullable(result);
         }
 
         /** {@inheritDoc} */
         @Override
         public Optional<Map<String, Object>> queryFirst(String sql, Object[] params)
                 throws SQLException {
-            return JdbcOperationSupport.queryFirst(this.conn, sql, params, RowMapper.HASH_MAP_MAPPER);
+            final Map<String, Object> result = JdbcOperationSupport
+                    .queryFirst(this.conn, sql, params, RowMapper.HASH_MAP_MAPPER);
+            return Optional.ofNullable(result);
         }
 
         /** {@inheritDoc} */
         @Override
         public Optional<DbRecord> queryFirstRecord(String sql, Object[] params)
                 throws SQLException {
-            return JdbcOperationSupport.queryFirst(this.conn, sql, params, RowMapper.RECORD_MAPPER);
+            final DbRecord result = JdbcOperationSupport
+                    .queryFirst(this.conn, sql, params, RowMapper.RECORD_MAPPER);
+            return Optional.ofNullable(result);
         }
 
         /** {@inheritDoc} */
         @Override
         public Optional<String> queryFirstString(String sql, Object[] params)
                 throws SQLException {
-            return JdbcOperationSupport.queryFirstString(this.conn, sql, params);
+            final String result = JdbcOperationSupport.queryFirstString(this.conn, sql, params);
+            return Optional.ofNullable(result);
         }
 
         /** {@inheritDoc} */
         @Override
         public OptionalInt queryFirstInt(String sql, Object[] params)
                 throws SQLException {
-            return JdbcOperationSupport.queryFirstInt(this.conn, sql, params);
+            final Integer result = JdbcOperationSupport.queryFirstInt(this.conn, sql, params);
+            return OptionalTools.optionalOf(result);
         }
 
         /** {@inheritDoc} */
         @Override
         public OptionalLong queryFirstLong(String sql, Object[] params)
                 throws SQLException {
-            return JdbcOperationSupport.queryFirstLong(this.conn, sql, params);
+            final Long result = JdbcOperationSupport.queryFirstLong(this.conn, sql, params);
+            return OptionalTools.optionalOf(result);
         }
 
         /** {@inheritDoc} */
         @Override
         public OptionalDouble queryFirstDouble(String sql, Object[] params)
                 throws SQLException {
-            return JdbcOperationSupport.queryFirstDouble(this.conn, sql, params);
+            final Double result = JdbcOperationSupport.queryFirstDouble(this.conn, sql, params);
+            return OptionalTools.optionalOf(result);
         }
 
         /** {@inheritDoc} */
         @Override
         public Optional<BigDecimal> queryFirstBigDecimal(String sql, Object[] params)
                 throws SQLException {
-            return JdbcOperationSupport.queryFirstBigDecimal(this.conn, sql, params);
+            final BigDecimal result = JdbcOperationSupport.queryFirstBigDecimal(this.conn, sql, params);
+            return Optional.ofNullable(result);
         }
 
         /** {@inheritDoc} */
         @Override
         public <T> Optional<T> queryFirst(String sql, RowMapper<T> rowMapper)
                 throws SQLException {
-            return JdbcOperationSupport.queryFirst(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, rowMapper);
+            final T result = JdbcOperationSupport
+                    .queryFirst(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, rowMapper);
+            return Optional.ofNullable(result);
         }
 
         /** {@inheritDoc} */
         @Override
         public <T> Optional<T> queryFirst(String sql, Class<T> clazz)
                 throws SQLException {
-            return JdbcOperationSupport.queryFirst(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, clazz);
+            final T result = JdbcOperationSupport
+                    .queryFirst(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, clazz);
+            return Optional.ofNullable(result);
         }
 
         /** {@inheritDoc} */
         @Override
         public Optional<Map<String, Object>> queryFirst(String sql)
                 throws SQLException {
-            return JdbcOperationSupport.queryFirst(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, RowMapper.HASH_MAP_MAPPER);
+            final Map<String, Object> result = JdbcOperationSupport
+                    .queryFirst(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, RowMapper.HASH_MAP_MAPPER);
+            return Optional.ofNullable(result);
         }
 
         /** {@inheritDoc} */
         @Override
         public Optional<DbRecord> queryFirstRecord(String sql)
                 throws SQLException {
-            return JdbcOperationSupport.queryFirst(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, RowMapper.RECORD_MAPPER);
+            final DbRecord result = JdbcOperationSupport
+                    .queryFirst(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY, RowMapper.RECORD_MAPPER);
+            return Optional.ofNullable(result);
         }
 
         /** {@inheritDoc} */
         @Override
         public Optional<String> queryFirstString(String sql)
                 throws SQLException {
-            return JdbcOperationSupport.queryFirstString(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            final String result = JdbcOperationSupport
+                    .queryFirstString(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            return Optional.ofNullable(result);
         }
 
         /** {@inheritDoc} */
         @Override
         public OptionalInt queryFirstInt(String sql)
                 throws SQLException {
-            return JdbcOperationSupport.queryFirstInt(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            final Integer result = JdbcOperationSupport
+                    .queryFirstInt(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            return OptionalTools.optionalOf(result);
         }
 
         /** {@inheritDoc} */
         @Override
         public OptionalLong queryFirstLong(String sql)
                 throws SQLException {
-            return JdbcOperationSupport.queryFirstLong(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            final Long result = JdbcOperationSupport
+                    .queryFirstLong(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            return OptionalTools.optionalOf(result);
         }
 
         /** {@inheritDoc} */
         @Override
         public OptionalDouble queryFirstDouble(String sql)
                 throws SQLException {
-            return JdbcOperationSupport.queryFirstDouble(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            final Double result = JdbcOperationSupport
+                    .queryFirstDouble(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            return OptionalTools.optionalOf(result);
         }
 
         /** {@inheritDoc} */
         @Override
         public Optional<BigDecimal> queryFirstBigDecimal(String sql)
                 throws SQLException {
-            return JdbcOperationSupport.queryFirstBigDecimal(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            final BigDecimal result = JdbcOperationSupport
+                    .queryFirstBigDecimal(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            return Optional.ofNullable(result);
+        }
+
+        /** {@inheritDoc} */
+        @Override
+        public boolean queryAsBoolean(String sql)
+                throws SQLException {
+            final Boolean result = JdbcOperationSupport
+                    .queryFirstBoolean(this.conn, sql, ParamBuilder.EMPTY_OBJECT_ARRAY);
+            return Boolean.TRUE.equals(result);
+        }
+
+        /** {@inheritDoc} */
+        @Override
+        public boolean queryAsBoolean(String sql, Object[] params)
+                throws SQLException {
+            final Boolean result = JdbcOperationSupport.queryFirstBoolean(this.conn, sql, params);
+            return Boolean.TRUE.equals(result);
         }
 
         // #endregion
@@ -703,10 +810,12 @@ public class SimpleJdbcTemplate implements JdbcOperations {
 
         /** {@inheritDoc} */
         @Override
-        public List<int[]> batchUpdateAndIgnoreException(String sql, @Nullable Collection<Object[]> params,
-                int batchSize, List<Exception> exceptions)
-                throws SQLException {
-            return JdbcOperationSupport.batchUpdateAndIgnoreException(this.conn, sql, params, batchSize, exceptions);
+        public List<int[]> batchUpdateAndIgnoreException(String sql,
+                                                         @Nullable Collection<Object[]> params,
+                                                         int batchSize,
+                                                         List<Exception> exceptions) throws SQLException {
+            return JdbcOperationSupport
+                    .batchUpdateAndIgnoreException(this.conn, sql, params, batchSize, exceptions);
         }
 
         // #endregion

src/test/java/xyz/zhouxy/jdbc/test/SimpleJdbcTemplateTests.java

@@ -108,6 +108,14 @@ class SimpleJdbcTemplateTests {
         );
     }
 
+    @Test
+    void testQueryExists() throws SQLException {
+        boolean isExists = jdbcTemplate.queryAsBoolean(
+                "SELECT EXISTS(SELECT 1 FROM sys_account WHERE id = ? LIMIT 1)",
+                buildParams(998));
+        assertFalse(isExists);
+    }
+
     @Test
     void testInsert() throws SQLException {
         List<Map<String, Object>> keys = jdbcTemplate.update(