需要增加一个是否存在的查询API：exists (#59)

sqli-core/src/main/java/io/xream/sqli/api/BaseRepository.java

@@ -113,5 +113,6 @@ public interface BaseRepository<T> extends Typed<T> {
      */
     <T> void findToHandle(Criteria criteria, RowHandler<T> handler);
 
-
+    boolean exists(Criteria criteria);
+
 }

sqli-core/src/main/java/io/xream/sqli/core/Repository.java

@@ -92,4 +92,6 @@ public interface Repository extends QueryForCache {
 	void findToHandle(Criteria.ResultMapCriteria resultMapCriteria, RowHandler<Map<String, Object>> handler);
 
 	<T> List<T> listByClzz(Class<T> clzz);
+
+	boolean exists(Criteria criteria);
 }

sqli-repo/src/main/java/io/xream/sqli/repository/core/CacheableRepository.java

@@ -362,4 +362,8 @@ public void findToHandle(Criteria.ResultMapCriteria criteria, RowHandler<Map<Str
         this.dao.findToHandle(criteria,handler);
     }
 
+    @Override
+    public boolean exists(Criteria criteria) {
+        return this.dao.exists(criteria);
+    }
 }

sqli-repo/src/main/java/io/xream/sqli/repository/dao/Dao.java

@@ -74,4 +74,6 @@ List<Map<String,Object>>  list(String sql,
 
 	<T> void findToHandle(Criteria criteria, RowHandler<T> handler);
 	void findToHandle(Criteria.ResultMapCriteria resultMapCriteria, RowHandler<Map<String, Object>> handler);
+
+    boolean exists(Criteria criteria);
 }

sqli-repo/src/main/java/io/xream/sqli/repository/dao/DaoImpl.java

@@ -418,6 +418,21 @@ public <T> void findToHandle(Criteria criteria, RowHandler<T> handler) {
         this.jdbcHelper.queryForMapToHandle(sql, valueList, dialect,null, Parser.get(clz), handler);
     }
 
+    @Override
+    public boolean exists(Criteria criteria) {
+
+        Class clz = criteria.getClzz();
+        List<Object> valueList = new ArrayList<>();
+        SqlBuilt sqlBuilt = sqlBuilder.buildQueryByCriteria(valueList,criteria, criteriaToSql, dialect);
+        String sql = sqlBuilt.getSql().toString();
+        sql = sql.replace("*","1");
+        sql += " LIMIT 1";
+        SqliLoggerProxy.debug(clz, sql);
+
+        List<Long> list = this.jdbcHelper.queryForPlainValueList(Long.class, sql, valueList,this.dialect);
+
+        return ! list.isEmpty();
+    }
 
     private boolean update(String sql, Collection<Object> list, Dialect dialect, JdbcHelper jdbcHelper) {
         try {

sqli-repo/src/main/java/io/xream/sqli/repository/internal/DefaultRepository.java

@@ -279,6 +279,12 @@ public <T> void findToHandle(Criteria criteria, RowHandler<T> handler) {
         this.repository.findToHandle(criteria,handler);
     }
 
+    @Override
+    public boolean exists(Criteria criteria) {
+        assertCriteriaClzz(criteria);
+        this.setDefaultClzz(criteria);
+        return this.repository.exists(criteria);
+    }
 
     @Override
     public Page<Map<String, Object>> find(Criteria.ResultMapCriteria resultMapCriteria) {