* 数据库操作助手类
*/
public class DatabaseHelper {
private static final Logger LOGGER = LoggerFactory.getLogger(DatabaseHelper.
class);
private static final ThreadLocal<Connection>
CONNECTION_HOLDER;
private static final QueryRunner QUERY_RUNNER;
private static final BasicDataSource DATA_SOURCE;
static {
CONNECTION_HOLDER =
new ThreadLocal<Connection>
();
QUERY_RUNNER =
new QueryRunner();
DATA_SOURCE =
new BasicDataSource();
Properties conf = PropsUtil.loadProps("config.properties"
);
String driver = conf.getProperty("jdbc.driver"
);
String url = conf.getProperty("jdbc.url"
);
String username = conf.getProperty("jdbc.username"
);
String password = conf.getProperty("jdbc.password"
);
DATA_SOURCE.setDriverClassName(driver);
DATA_SOURCE.setUrl(url);
DATA_SOURCE.setUsername(username);
DATA_SOURCE.setPassword(password);
}
/**
* 获取数据库连接
*/
public static Connection getConnection() {
Connection connection =
CONNECTION_HOLDER.get();
if (connection ==
null) {
try {
connection =
DATA_SOURCE.getConnection();
} catch (SQLException e) {
LOGGER.error("get connection failure"
, e);
throw new RuntimeException(e);
} finally {
CONNECTION_HOLDER.set(connection);
}
}
return connection;
}
/**
* 查询实体列表
*/
public static <T> List<T> queryEntityList(Class<T>
entityClass, String sql, Object... params) {
List<T>
entityList;
try {
Connection conn =
getConnection();
entityList = QUERY_RUNNER.query(conn, sql,
new BeanListHandler<T>
(entityClass), params);
} catch (SQLException e) {
LOGGER.error("query entity list failure"
, e);
throw new RuntimeException(e);
}
return entityList;
}
/**
* 查询实体
*/
public static <T> T queryEntity(Class<T>
entityClass, String sql, Object... params) {
T entity;
try {
Connection connection =
getConnection();
entity = QUERY_RUNNER.query(connection, sql,
new BeanHandler<T>
(entityClass), params);
} catch (SQLException e) {
LOGGER.error("query entity failure"
, e);
throw new RuntimeException(e);
}
return entity;
}
/**
* 执行查询语句
*/
public static List<Map<String, Object>>
executeQuery(String sql, Object... params) {
List<Map<String, Object>>
result;
try {
Connection connection =
getConnection();
result = QUERY_RUNNER.query(connection, sql,
new MapListHandler(), params);
} catch (Exception e) {
LOGGER.error("execute query failure"
, e);
throw new RuntimeException(e);
}
return result;
}
/**
* 执行更新语句（update、insert、delete）
*/
public static int executeUpdate(String sql, Object... params) {
int rows = 0
;
try {
Connection connection =
getConnection();
rows =
QUERY_RUNNER.update(connection, sql, params);
} catch (SQLException e) {
LOGGER.error("execute update failure"
, e);
throw new RuntimeException(e);
}
return rows;
}
/**
* 插入实体
*/
public static <T>
boolean insertEntity(Class<T> entityClass, Map<String, Object>
fieldMap) {
if (CollectionUtil.isEmpty(fieldMap)) {
LOGGER.error("can not insert entity: fieldMap is empty"
);
return false;
}
String sql = "insert into " +
getTableName(entityClass);
StringBuilder columns =
new StringBuilder(" ("
);
StringBuilder values =
new StringBuilder(" ("
);
for (String fieldName : fieldMap.keySet()) {
columns.append(fieldName).append(", "
);
values.append("?, "
);
}
columns.replace(columns.lastIndexOf(", "), columns.length(), ") "
);
values.replace(values.lastIndexOf(", "), values.length(), ") "
);
sql += columns + " values " +
values;
Object[] params =
fieldMap.values().toArray();
return executeUpdate(sql, params) == 1
;
}
/**
* 更新实体
*/
public static <T>
boolean updateEntity(Class<T> entityClass,
long id, Map<String, Object>
fieldMap) {
if (CollectionUtil.isEmpty(fieldMap)) {
LOGGER.error("can not update entity: fieldMap is empty"
);
return false;
}
String sql = "update " + getTableName(entityClass) + " set "
;
StringBuilder columns =
new StringBuilder();
for (String fieldName : fieldMap.keySet()) {
columns.append(fieldName).append("=?, "
);
}
sql += columns.substring(0, columns.lastIndexOf(", ")) + " where id=?"
;
List<Object> paramList =
new ArrayList<Object>
();
paramList.addAll(fieldMap.values());
paramList.add(id);
Object[] params =
paramList.toArray();
return executeUpdate(sql, params) == 1
;
}
/**
* 删除实体
*/
public static <T>
boolean deleteEntity(Class<T> entityClass,
long id) {
String sql = "delete from " + getTableName(entityClass) + " where id=?"
;
return executeUpdate(sql, id) == 1
;
}
/**
* 通过类名获取表名
*/
private static String getTableName(Class<?>
entityClass) {
return entityClass.getSimpleName();
}
/**
* 执行SQL文件
*/
public static void executeSqlFile(String filePath) {
InputStream is =
Thread.currentThread().getContextClassLoader().getResourceAsStream(filePath);
BufferedReader reader =
new BufferedReader(
new InputStreamReader(is));
try {
String sql;
while ((sql = reader.readLine()) !=
null) {
executeUpdate(sql);
}
} catch (IOException e) {
LOGGER.error("execute sql file failure"
, e);
throw new RuntimeException(e);
}
}
}
DatabaseHelper
相关代码下载
需要关注的地方
1、ThreadLocal<Connection>
泛型内指定存储数据类型
2、数据库连接对象创建后不再关闭，交由BasicDataSource管理
3、java中泛型T和？
T用于指定参数类型或返回类型，泛型方法要在方法名前标记<T>
?用于泛型类型指定，如Class<?>，任意类型的Class类；List<?> list，任意类型集合
使用ThreadLocal、Apache的dbutils的QueryRunner和dbcp2数据库连接池的BasicDataSource封装操作数据库工具
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