见贤思齐焉,孔老夫子诚不欺我。
第一 你得见----------------------------你都不知道有这个项目,那就什么都不用说了
井鼃不可以语于海者，拘于虚也；夏虫不可以语于冰者，笃于时也；曲士不可以语于道者，束于教也。
第二 那个工程必须真的贤-----------跟臭棋篓子下棋,越下越臭
第三 你得思-------------------------------把自己的糟糕的代码拉出来,跟"贤明"的代码比一比。别嫌丢人,哪个程序员不是从hello world起步的?
(上面的教程相当全,初级使用我认为只看前三节即可)
@Test
public void testBeanHandlerByDBSource() {
QueryRunner qr = new QueryRunner(new MyDBSource());
Student student = qr.query("select * from student where xh='02'", new BeanHandler<>(
Student.class));
System.out.println(student.getXm() + " " + student.getXh()+" "+student.getBirth());
}其中MyDBSource只是一个获取数据源的工具类而已。public class MyDBSource implements DataSource {
private static String driverClassName = "com.mysql.jdbc.Driver";
private static String url = "jdbc:mysql://localhost:3306/webexample";
private static String userName = "root";
private static String passWord = "root";
@Override
public Connection getConnection() throws SQLException {
try {
Class.forName(driverClassName);
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return DriverManager.getConnection(url, userName, passWord);
}
}我们看看QueryRunner的构造函数public class QueryRunner {
private Connection connection;
public QueryRunner(){
}
public QueryRunner(DataSource ds){
try {
connection=ds.getConnection();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
//...
}现在看重头戏,就是QueryRunner的一系列query方法public class QueryRunner {
public <T> T query(String sql, ResultSetHandler<T> rsh) {
if (connection!=null) {
return query(connection, sql, rsh);
}else {
System.out.println("connection is null!");
return null;
}
}
public <T> T query(Connection conn, String sql, ResultSetHandler<T> rsh) {
return query(conn, sql, new Object[]{}, rsh);
}
public <T> T query(Connection conn, String sql, Object[] params, ResultSetHandler<T> rsh){
T object=null;
try{
PreparedStatement ps=conn.prepareStatement(sql);
for (int i = 0; i < params.length; i++) {
setParams(ps, i,params);
}
ResultSet rs=ps.executeQuery();
object=rsh.handle(rs);
}catch (Exception e) {
e.printStackTrace();
}
return object;
}
}
//为了方便,我这里只模拟了String与date型的数据
public void setParams(PreparedStatement ps,int i,Object[] params){
try {
if (params[i] instanceof String) {
ps.setString(i+1, (String) params[i]);
}
if (params[i] instanceof java.util.Date) {
ps.setDate(i+1, (Date) params[i]);
}
} catch (Exception e) {
e.printStackTrace();
}
}object=rsh.handle(rs);在junit中,我们给QueryRunner里面注入的就是BeanHandler类。
public class BeanHandler<T> implements ResultSetHandler<T>{
private Class<T> type;
public BeanHandler(Class<T> type)
this.type=type;
}
@Override
public T handle(ResultSet rs) throws SQLException {
T o=null;
try {
while (rs.next()) {
o=BeanUtils.creatBean(rs, type);
}
} catch (Exception e) {
e.printStackTrace();
}
return o;
}
}
//BeanUtils.java
public class BeanUtils {
public static <T> T creatBean(ResultSet rs, Class<T> type) {
T o = null;
try {
o = type.newInstance();
Field[] field = type.getDeclaredFields();
for (int i = 0; i < field.length; i++) {
String filedName = field[i].getName();
Class<?> filedType = field[i].getType();
String methodName = "set"
+ filedName.substring(0, 1).toUpperCase()
+ filedName.substring(1);
Method m = type.getDeclaredMethod(methodName, filedType);
Object value=setValue(filedType,rs,filedName);
m.invoke(o, value);
}
} catch (Exception e) {
e.printStackTrace();
}
return o;
}
public static Object setValue( Class<?> filedType, ResultSet rs, String filedName){
Object value=null;
try {
if (filedType.getName().equals("java.lang.String")) {
value = rs.getString(filedName);
}
if (filedType.getName().equals("java.util.Date")) {
value = rs.getDate(filedName);
}
} catch (Exception e) {
e.printStackTrace();
}
return value;
}
}
上面的代码,怎么说呢,我也不嫌贻笑大方。
慢慢来嘛#
下面的是对dbutis源码浅层次的分析:
http://blog.csdn.net/dlf123321/article/details/45172429
接下来,我就来比较一下,看看人家有多么牛逼,我自己有多么low
原文地址：http://blog.csdn.net/dlf123321/article/details/45173505
