OSChina 使用的是 dbutils 这个JDBC的封装类库来进行数据库操作。而 QueryHelper 则是在 dbutils 的基础上进行一级简单的封装，提供一些常用的数据库操作方法和对数据缓存的支持。
红薯...QueryHelper 代码如下：
package my.db;
import java.io.Serializable;
import java.math.BigInteger;
import java.sql.*;
import java.util.*;
import my.cache.CacheManager;
import net.oschina.Configurations;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.*;
import org.apache.commons.lang.ArrayUtils;
/**
* 数据库查询助手
* @author Winter Lau<br> */
@SuppressWarnings("unchecked")
public class QueryHelper {
private final static QueryRunner _g_runner = new QueryRunner();
private final static ColumnListHandler _g_columnListHandler = new ColumnListHandler(){
@Override
protected Object handleRow(ResultSet rs) throws SQLException {
Object obj = super.handleRow(rs);
if(obj instanceof BigInteger)
return ((BigInteger)obj).longValue();
return obj;
}
};
private final static ScalarHandler _g_scaleHandler = new ScalarHandler(){
@Override
public Object handle(ResultSet rs) throws SQLException {
Object obj = super.handle(rs);
if(obj instanceof BigInteger)
return ((BigInteger)obj).longValue();
return obj;
}
};
private final static List<Class<?>> PrimitiveClasses = new ArrayList<Class<?>>(){{
add(Long.class);
add(Integer.class);
add(String.class);
add(java.util.Date.class);
add(java.sql.Date.class);
add(java.sql.Timestamp.class);
}};
private final static boolean _IsPrimitive(Class<?> cls) {
return cls.isPrimitive() || PrimitiveClasses.contains(cls) ;
}
/**
* 获取数据库连接
* @return
*/
public static Connection getConnection() {
try{
return Configurations.getConnection();
}catch(SQLException e){
throw new DBException(e);
}
}
/**
* 读取某个对象
* @param sql
* @param params
* @return
*/
@SuppressWarnings("rawtypes")
public static <T> T read(Class<T> beanClass, String sql, Object...params) {
try{
return (T)_g_runner.query(getConnection(), sql, _IsPrimitive(beanClass)?_g_scaleHandler:new BeanHandler(beanClass), params);
}catch(SQLException e){
throw new DBException(e);
}
}
public static <T> T read_cache(Class<T> beanClass, String cache, Serializable key, String sql, Object...params) {
T obj = (T)CacheManager.get(cache, key);
if(obj == null){
obj = read(beanClass, sql, params);
CacheManager.set(cache, key, (Serializable)obj);
}
return obj;
}
/**
* 对象查询
* @param <T>
* @param beanClass
* @param sql
* @param params
* @return
*/
@SuppressWarnings("rawtypes")
public static <T> List<T> query(Class<T> beanClass, String sql, Object...params) {
try{
return (List<T>)_g_runner.query(getConnection(), sql, _IsPrimitive(beanClass)?_g_columnListHandler:new BeanListHandler(beanClass), params);
}catch(SQLException e){
throw new DBException(e);
}
}
/**
* 支持缓存的对象查询
* @param <T>
* @param beanClass
* @param cache_region
* @param key
* @param sql
* @param params
* @return
*/
public static <T> List<T> query_cache(Class<T> beanClass, String cache_region, Serializable key, String sql, Object...params) {
List<T> objs = (List<T>)CacheManager.get(cache_region, key);
if(objs == null){
objs = query(beanClass, sql, params);
CacheManager.set(cache_region, key, (Serializable)objs);
}
return objs;
}
/**
* 分页查询
* @param <T>
* @param beanClass
* @param sql
* @param page
* @param count
* @param params
* @return
*/
public static <T> List<T> query_slice(Class<T> beanClass, String sql, int page, int count, Object...params) {
if(page < 0 || count < 0)
throw new IllegalArgumentException("Illegal parameter of 'page' or 'count', Must be positive.");
int from = (page - 1) * count;
count = (count > 0) ? count : Integer.MAX_VALUE;
return query(beanClass, sql + " LIMIT ?,?", ArrayUtils.addAll(params, new Integer[]{from,count}));
}
/**
* 支持缓存的分页查询
* @param <T>
* @param beanClass
* @param cache
* @param cache_key
* @param cache_obj_count
* @param sql
* @param page
* @param count
* @param params
* @return
*/
public static <T> List<T> query_slice_cache(Class<T> beanClass, String cache, Serializable cache_key, int cache_obj_count, String sql, int page, int count, Object...params) {
List<T> objs = (List<T>)CacheManager.get(cache, cache_key);
if(objs == null) {
objs = query_slice(beanClass, sql, 1, cache_obj_count, params);
CacheManager.set(cache, cache_key, (Serializable)objs);
}
if(objs == null || objs.size()==0)
return objs;
int from = (page - 1) * count;
if(from < 0)
return null;
if((from+count) > cache_obj_count)//超出缓存的范围
return query_slice(beanClass, sql, page, count, params);
int end = Math.min(from + count, objs.size());
if(from >= end)
return null;
return objs.subList(from, end);
}
/**
* 执行统计查询语句，语句的执行结果必须只返回一个数值
* @param sql
* @param params
* @return
*/
public static long stat(String sql, Object...params) {
try{
Number num = (Number)_g_runner.query(getConnection(), sql, _g_scaleHandler, params);
return (num!=null)?num.longValue():-1;
}catch(SQLException e){
throw new DBException(e);
}
}
/**
* 执行统计查询语句，语句的执行结果必须只返回一个数值
* @param cache_region
* @param key
* @param sql
* @param params
* @return
*/
public static long stat_cache(String cache_region, Serializable key, String sql, Object...params) {
Number value = (Number)CacheManager.get(cache_region, key);
if(value == null){
value = stat(sql, params);
CacheManager.set(cache_region, key, value);
}
return value.longValue();
}
/**
* 执行INSERT/UPDATE/DELETE语句
* @param sql
* @param params
* @return
*/
public static int update(String sql, Object...params) {
try{
return _g_runner.update(getConnection(), sql, params);
}catch(SQLException e){
throw new DBException(e);
}
}
/**
* 批量执行指定的SQL语句
* @param sql
* @param params
* @return
*/
public static int[] batch(String sql, Object[][] params) {
try{
return _g_runner.batch(getConnection(), sql, params);
}catch(SQLException e){
throw new DBException(e);
}
}
}
该类主要提供包括查询列表、查询列表分页、查询单条记录、统计等方法的封装。
