基于Java语言的23种经典设计模式源码分析

package org.itstack.demo.design.mediator; import java.lang.reflect.Field; import java.lang.reflect.Method; import java.sql.*; import java.util.Date; import java.util.*; /** * 公众号 | bugstack虫洞栈 * 博 客 | https://bugstack.cn * Create by 小傅哥 @2020 */ public class DefaultSqlSession implements SqlSession { private Connection connection; private Map<String, XNode> mapperElement; public DefaultSqlSession(Connection connection, Map<String, XNode> mapperElement) { this.connection = connection; this.mapperElement = mapperElement; } @Override public <T> T selectOne(String statement) { try { XNode xNode = mapperElement.get(statement); PreparedStatement preparedStatement = connection.prepareStatement(xNode.getSql()); ResultSet resultSet = preparedStatement.executeQuery(); List<T> objects = resultSet2Obj(resultSet, Class.forName(xNode.getResultType())); return objects.get(0); } catch (Exception e) { e.printStackTrace(); } return null; } @Override public <T> T selectOne(String statement, Object parameter) { XNode xNode = mapperElement.get(statement); Map<Integer, String> parameterMap = xNode.getParameter(); try { PreparedStatement preparedStatement = connection.prepareStatement(xNode.getSql()); buildParameter(preparedStatement, parameter, parameterMap); ResultSet resultSet = preparedStatement.executeQuery(); List<T> objects = resultSet2Obj(resultSet, Class.forName(xNode.getResultType())); return objects.get(0); } catch (Exception e) { e.printStackTrace(); } return null; } @Override public <T> List<T> selectList(String statement) { XNode xNode = mapperElement.get(statement); try { PreparedStatement preparedStatement = connection.prepareStatement(xNode.getSql()); ResultSet resultSet = preparedStatement.executeQuery(); return resultSet2Obj(resultSet, Class.forName(xNode.getResultType())); } catch (Exception e) { e.printStackTrace(); } return null; } @Override public <T> List<T> selectList(String statement, Object parameter) { XNode xNode = mapperElement.get(statement); Map<Integer, String> parameterMap = xNode.getParameter(); try { PreparedStatement preparedStatement = connection.prepareStatement(xNode.getSql()); buildParameter(preparedStatement, parameter, parameterMap); ResultSet resultSet = preparedStatement.executeQuery(); return resultSet2Obj(resultSet, Class.forName(xNode.getResultType())); } catch (Exception e) { e.printStackTrace(); } return null; } private void buildParameter(PreparedStatement preparedStatement, Object parameter, Map<Integer, String> parameterMap) throws SQLException, IllegalAccessException { int size = parameterMap.size(); // 单个参数 if (parameter instanceof Long) { for (int i = 1; i <= size; i++) { preparedStatement.setLong(i, Long.parseLong(parameter.toString())); } return; } if (parameter instanceof Integer) { for (int i = 1; i <= size; i++) { preparedStatement.setInt(i, Integer.parseInt(parameter.toString())); } return; } if (parameter instanceof String) { for (int i = 1; i <= size; i++) { preparedStatement.setString(i, parameter.toString()); } return; } Map<String, Object> fieldMap = new HashMap<>(); // 对象参数 Field[] declaredFields = parameter.getClass().getDeclaredFields(); for (Field field : declaredFields) { String name = field.getName(); field.setAccessible(true); Object obj = field.get(parameter); field.setAccessible(false); fieldMap.put(name, obj); } for (int i = 1; i <= size; i++) { String parameterDefine = parameterMap.get(i); Object obj = fieldMap.get(parameterDefine); if (obj instanceof Short) { preparedStatement.setShort(i, Short.parseShort(obj.toString())); continue; } if (obj instanceof Integer) { preparedStatement.setInt(i, Integer.parseInt(obj.toString())); continue; } if (obj instanceof Long) { preparedStatement.setLong(i, Long.parseLong(obj.toString())); continue; } if (obj instanceof String) { preparedStatement.setString(i, obj.toString()); continue; } if (obj instanceof Date) { preparedStatement.setDate(i, (java.sql.Date) obj); } } } private <T> List<T> resultSet2Obj(ResultSet resultSet, Class<?> clazz) { List<T> list = new ArrayList<>(); try { ResultSetMetaData metaData = resultSet.getMetaData(); int columnCount = metaData.getColumnCount(); // 每次遍历行值 while (resultSet.next()) { T obj = (T) clazz.newInstance(); for (int i = 1; i <= columnCount; i++) { Object value = resultSet.getObject(i); String columnName = metaData.getColumnName(i); String setMethod = "set" + columnName.substring(0, 1).toUpperCase() + columnName.substring(1); Method method; if (value instanceof Timestamp) { method = clazz.getMethod(setMethod, Date.class); } else { method = clazz.getMethod(setMethod, value.getClass()); } method.invoke(obj, value); } list.add(obj); } } catch (Exception e) { e.printStackTrace(); } return list; } @Override public void close() { if (null == connection) return; try { connection.close(); } catch (SQLException e) { e.printStackTrace(); } } }