基于java的学生信息管理系统.zip

package com.kfm.util; import java.beans.PropertyDescriptor; import java.io.IOException; import java.io.InputStream; import java.lang.reflect.Constructor; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.sql.*; import java.util.ArrayList; import java.util.Arrays; import java.util.List; import java.util.Properties; public class DBUtil<T> { public static Object queryOne; private static String url; private static String user; private static String password; private Connection conn; private PreparedStatement ps; static{ InputStream inputStream = DBUtil.class.getClassLoader().getResourceAsStream("db.properties"); Properties prop = new Properties(); try { prop.load(inputStream); url = prop.getProperty("url"); user = prop.getProperty("user"); password = prop.getProperty("password"); Class.forName(prop.getProperty("driver")); } catch (IOException e) { e.printStackTrace(); } catch (ClassNotFoundException e) { e.printStackTrace(); } } public Connection getConnection(){ if (conn == null){ try { conn = DriverManager.getConnection(url, user, password); } catch (SQLException e) { e.printStackTrace(); } } return conn; } public ResultSet query(String sql, Object...params) throws SQLException { getConnection(); if (sql != null){ ps = conn.prepareStatement(sql); setParams(params); System.out.println(ps); return ps.executeQuery(); } return null; } public T queryOne(String sql, Class<T> cla, Object...params) throws SQLException { ResultSet query = query(sql, params); if (query != null && query.next()){ return mapper(query, cla); } return null; // List<T> ts = queryList(sql, cla, params); // return ts.size() > 0? ts.get(0) : null; } public List<T> queryList(String sql, Class<T> cla, Object...params) throws SQLException { ResultSet query = query(sql, params); List<T> list = new ArrayList<>(); while(query != null && query.next()){ T mapper = mapper(query, cla); list.add(mapper); } return list; } private T mapper(ResultSet resultSet, Class<T> cla){ try { Constructor<T> declaredConstructor = cla.getDeclaredConstructor(); T t = declaredConstructor.newInstance(); ResultSetMetaData metaData = resultSet.getMetaData(); // 迭代结果集中的所有列 for (int i = 1; i <= metaData.getColumnCount(); i ++){ // 获取当前的 列名 String columnLabel = metaData.getColumnLabel(i); Object value = resultSet.getObject(columnLabel); try { // 数据库字段 --> java 字段 if (columnLabel.contains("_")){ // create_account => createAccount columnLabel = toCamel(columnLabel); } // 获取列名在 class 中对应的 属性 PropertyDescriptor pd = new PropertyDescriptor(columnLabel, cla); // 获取 setter 方法 Method writeMethod = pd.getWriteMethod(); // 设置值 writeMethod.invoke(t, value); } catch (Exception e){ e.printStackTrace(); System.err.println(columnLabel + " 属性设置值失败"); } } return t; } catch (Exception e) { e.printStackTrace(); } return null; } private String toCamel(String label){ // create_account => create, account String[] s = label.split("_"); // 结果 StringBuffer sb = new StringBuffer(s[0]); for (int i = 1; i < s.length; i++) { // 单词 sb.append(s[i].substring(0, 1).toUpperCase() + s[i].substring(1)); } return sb.toString(); } public int update(String sql, Object...params) throws SQLException { getConnection(); ps = conn.prepareStatement(sql); setParams(params); System.out.println(ps); return ps.executeUpdate(); } public int save(String sql, boolean isReturnKey, Object...params) throws SQLException { getConnection(); ps = conn.prepareStatement(sql, isReturnKey ? Statement.RETURN_GENERATED_KEYS : Statement.NO_GENERATED_KEYS); setParams(params); System.out.println(ps); int row = ps.executeUpdate(); if (isReturnKey){ // 获取自增主键 ResultSet generatedKeys = ps.getGeneratedKeys(); if (generatedKeys.next()){ return generatedKeys.getInt(1); } } return row; } private void setParams(Object...params) throws SQLException { // 设置值 for (int i = 0; i < params.length; i ++){ ps.setObject(i + 1, params[i]); } } public void close(){ try { if (ps != null){ ps.close(); } if (conn != null){ conn.close(); } } catch (SQLException e) { e.printStackTrace(); } } public static void main(String[] args) { String str = "hello_world_abc_efg"; String[] s = str.split("_"); // 结果 StringBuffer sb = new StringBuffer(s[0]); for (int i = 1; i < s.length; i++) { // 单词 sb.append(s[i].substring(0, 1).toUpperCase() + s[i].substring(1)); } System.out.println(sb.toString()); } }