# 数据库操作
这一小节是对数据库操作做一个简单的封装，不涉及复杂的事务操作等。
我选用了Sql2o作为底层数据库框架作为支持，它的简洁易用性让我刮目相看，后面我们也会写如何实现一个ORM框架。
```java
/**
* 数据库支持
* @author biezhi
*
*/
public final class MarioDb {
private static Sql2o sql2o = null;
private MarioDb() {
}
/**
* 初始化数据库配置
* @param url
* @param user
* @param pass
*/
public static void init(String url, String user, String pass){
sql2o = new Sql2o(url, user, pass);
}
/**
* 初始化数据库配置
* @param dataSource
*/
public static void init(DataSource dataSource){
sql2o = new Sql2o(dataSource);
}
/**
* 查询一个对象
* @param sql
* @param clazz
* @return
*/
public static <T> T get(String sql, Class<T> clazz){
return get(sql, clazz, null);
}
/**
* 查询一个列表
* @param sql
* @param clazz
* @return
*/
public static <T> List<T> getList(String sql, Class<T> clazz){
return getList(sql, clazz, null);
}
/**
* 查询一个对象返回为map类型
* @param sql
* @return
*/
public static Map<String, Object> getMap(String sql){
return getMap(sql, null);
}
/**
* 查询一个列表并返回为list<map>类型
* @param sql
* @return
*/
public static List<Map<String, Object>> getMapList(String sql){
return getMapList(sql, null);
}
/**
* 插入一条记录
* @param sql
* @param params
* @return
*/
public static int insert(String sql, Object ... params){
StringBuffer sqlBuf = new StringBuffer(sql);
sqlBuf.append(" values (");
int start = sql.indexOf("(") + 1;
int end = sql.indexOf(")");
String a = sql.substring(start, end);
String[] fields = a.split(",");
Map<String, Object> map = new HashMap<String, Object>();
int i=0;
for(String name : fields){
sqlBuf.append(":" + name.trim() + " ,");
map.put(name.trim(), params[i]);
i++;
}
String newSql = sqlBuf.substring(0, sqlBuf.length() - 1) + ")";
Connection con = sql2o.open();
Query query = con.createQuery(newSql);
executeQuery(query, map);
int res = query.executeUpdate().getResult();
con.close();
return res;
}
/**
* 更新
* @param sql
* @return
*/
public static int update(String sql){
return update(sql, null);
}
/**
* 带参数更新
* @param sql
* @param params
* @return
*/
public static int update(String sql, Map<String, Object> params){
Connection con = sql2o.open();
Query query = con.createQuery(sql);
executeQuery(query, params);
int res = query.executeUpdate().getResult();
con.close();
return res;
}
public static <T> T get(String sql, Class<T> clazz, Map<String, Object> params){
Connection con = sql2o.open();
Query query = con.createQuery(sql);
executeQuery(query, params);
T t = query.executeAndFetchFirst(clazz);
con.close();
return t;
}
@SuppressWarnings("unchecked")
public static Map<String, Object> getMap(String sql, Map<String, Object> params){
Connection con = sql2o.open();
Query query = con.createQuery(sql);
executeQuery(query, params);
Map<String, Object> t = (Map<String, Object>) query.executeScalar();
con.close();
return t;
}
public static List<Map<String, Object>> getMapList(String sql, Map<String, Object> params){
Connection con = sql2o.open();
Query query = con.createQuery(sql);
executeQuery(query, params);
List<Map<String, Object>> t = query.executeAndFetchTable().asList();
con.close();
return t;
}
public static <T> List<T> getList(String sql, Class<T> clazz, Map<String, Object> params){
Connection con = sql2o.open();
Query query = con.createQuery(sql);
executeQuery(query, params);
List<T> list = query.executeAndFetch(clazz);
con.close();
return list;
}
private static void executeQuery(Query query, Map<String, Object> params){
if (null != params && params.size() > 0) {
Set<String> keys = params.keySet();
for(String key : keys){
query.addParameter(key, params.get(key));
}
}
}
}
```
设计MVC框架部分已经完成，下一节是一个增删改查的例子
