JDBC简单封装
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/**
* JDBC简单封装
* 需要借助FastJsonUtil可以参考上一篇
* @author huangxincheng
*
*/
public class BaseDao {
private static String URL;
private static String USERNAME;
private static String PASSWORD;
private static String DRIVER;
private Connection connection;
private PreparedStatement pstmt;
private ResultSet result;
static {
try {
InputStream inputStream = BaseDao.class.getClassLoader().getResourceAsStream("jdbc.properties");
Properties prop = new Properties();
prop.load(inputStream);
USERNAME = prop.getProperty("jdbc.username");
PASSWORD = prop.getProperty("jdbc.password");
DRIVER= prop.getProperty("jdbc.driver");
URL = prop.getProperty("jdbc.url");
} catch (IOException e) {
throw new RuntimeException("load db properties faild");
}
}
//获取连接
private Connection getConnection() {
try {
Class.forName(DRIVER);// 注册驱动
connection = DriverManager.getConnection(URL, USERNAME, PASSWORD); // 获取连接
return connection;
} catch (Exception e) {
throw new RuntimeException("register db driver faild");
}
}
private PreparedStatement getStatement(String sql, Object ... objs) {
try {
pstmt = connection.prepareStatement(sql);
if (objs != null) {
for (int i = 0; i < objs.length; i++) {
pstmt.setObject(i+1, objs[i]);
}
}
return pstmt;
} catch (SQLException e) {
throw new RuntimeException("pstmt faild");
}
}
private <T> List<T> findResult(Class<T> clazz, String sql, Object ... objs) {
try {
getConnection();
getStatement(sql, objs);
result = pstmt.executeQuery();
ResultSetMetaData metaData = result.getMetaData();
int cols_len = metaData.getColumnCount();
List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();
Map<String, Object> map = null;
while (result.next()) {
map = new HashMap<String, Object>();
for (int i = 0; i < cols_len; i++) {
String cols_name = metaData.getColumnLabel(i + 1);
Object cols_value = result.getObject(cols_name);
if (cols_value == null) {
cols_value = "";
}
map.put(cols_name, cols_value);
}
list.add(map);
}
if (list.size() > 0) {
List<T> result = FactJsonUtil.parseList(FactJsonUtil.toJson(list), clazz);
return result;
}
return null;
} catch (SQLException e) {
throw new RuntimeException("result faild");
} finally {
releaseConn();
}
}
/**
* 释放资源
*/
private void releaseConn() {
if (result != null) {
try {
result.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (pstmt != null) {
try {
pstmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
@SuppressWarnings("main")
public static void main(String[] args) {
// List<TbTest> list = new BaseDao().findResult(TbTest.class, "select * from tb_test", null);
// for (TbTest tbTest : list) {
// System.out.println(tbTest.getId() + ":" + tbTest.getName() + ":" + tbTest.getSex());
// }
String sql = "SELECT"+
" t1.id as item_id,t1.title as item_title,"+
" t1.sell_point as item_sell_point,"+
" t1.price as item_price,"+
" t1.num as item_num,t1.image as item_image,"+
" t2.name as item_cname,"+
" t3.item_desc"+
" FROM"+
" tb_item t1"+
" LEFT JOIN tb_item_cat t2 ON t1.cid = t2.id"+
" LEFT JOIN tb_item_desc t3 ON t1.id = t3.item_id"+
" where t1.id = ?";
List<SolrItem> list = new BaseDao().findResult(SolrItem.class, sql, 844022);
if (list != null && list.size() > 0) {
for (SolrItem solrItem : list) {
System.err.println(solrItem);
}
}
}
}
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