JDBC 利用反射技术将查询结果封装为对象(简单ORM实现）

ORM（Object Relational Mapping）对象关系映射

public class ORMTest {

public static void main(String[] args) throws SQLException,

IllegalAccessException, InvocationTargetException, Exception {

User user = (User) getObject(

"select id as Id, name as Name, birthday as Birthday, money as Money  from user where id=1",

User.class);

System.out.println(user);

Bean b = (Bean) getObject(

"select id as Id, name as Name, birthday as Birthday, money as Money from user where id=1",

Bean.class);

System.out.println(b);

}

static List<Object> getObjects(String sql, Class clazz)

throws SQLException, Exception, IllegalAccessException,

InvocationTargetException {

Connection conn = null;

PreparedStatement ps = null;

ResultSet rs = null;

try {

conn = JdbcUtils.getConnection();

ps = conn.prepareStatement(sql);

rs = ps.executeQuery();

String[] colNames = getColNames(rs);

List<Object> objects = new ArrayList<Object>();

Method[] ms = clazz.getMethods();

while (rs.next()) {

Object object = clazz.newInstance();

for (int i = 0; i < colNames.length; i++) {

String colName = colNames[i];

String methodName = "set" + colName;

// Object value = rs.getObject(colName);

// try {

// Method m = clazz

// .getMethod(methodName, value.getClass());

// if (m != null)

// m.invoke(object, value);

// } catch (NoSuchMethodException e) {

// e.printStackTrace();

// //

// }

for (Method m : ms) {

if (methodName.equals(m.getName())) {

m.invoke(object, rs.getObject(colName));

break;

}

}

objects.add(object);

}

}

return objects;

} finally {

JdbcUtils.free(rs, ps, conn);

}

}

private static String[] getColNames(ResultSet rs) throws SQLException {

ResultSetMetaData rsmd = rs.getMetaData();

int count = rsmd.getColumnCount();

String[] colNames = new String[count];

for (int i = 1; i <= count; i++) {

colNames[i - 1] = rsmd.getColumnLabel(i);

}

return colNames;

}

static Object getObject(String sql, Class clazz) throws SQLException,

Exception, IllegalAccessException, InvocationTargetException {

Connection conn = null;

PreparedStatement ps = null;

ResultSet rs = null;

try {

conn = JdbcUtils.getConnection();

ps = conn.prepareStatement(sql);

rs = ps.executeQuery();

String[] colNames = getColNames(rs);

Object object = null;

Method[] ms = clazz.getMethods();

if (rs.next()) {

object = clazz.newInstance();

for (int i = 0; i < colNames.length; i++) {

String colName = colNames[i];

String methodName = "set" + colName;

// Object value = rs.getObject(colName);

// try {

// Method m = clazz

// .getMethod(methodName, value.getClass());

// if (m != null)

// m.invoke(object, value);

// } catch (NoSuchMethodException e) {

// e.printStackTrace();

// //

// }

for (Method m : ms) {

if (methodName.equals(m.getName())) {

m.invoke(object, rs.getObject(colName));

break;

}

}

}

}

return object;

} finally {

JdbcUtils.free(rs, ps, conn);

}

}

}