Java利用反射封装DBUtil，mysql万能增删改查工具类，附源码
等有时间再慢慢写代码注释吧，先把源码放出来。文章最后有整个项目的压缩包。
ps:拓展
Java 原生MySQL JDBC 插入后返回自增长ID，基于PreparedStatement executeUpdate
导览
1.仅关注DBUtil
看test + util + vo + myPro.properties
2.关注DBUtil怎么用在DAO中
看test + util + vo + myPro.properties + dao + daoImpl
2.仅关注DBUtil怎么用在Service中
看test + util + vo + myPro.properties + dao + daoImpl + service
DBUtil
util DBConnection 连接数据库
public class DBConnection {private static Connection conn;static {try {Properties properties = new Properties();//适用于任何情况下查找properties文件String propertiesPath = Objects.requireNonNull(DBConnection.class.getClassLoader().getResource("myPro.properties")).getPath().replace("%20"," ");properties.load(new FileInputStream(propertiesPath));//Java项目简单粗暴查找properties文件//String propertiesPath = "src/com/laner/myPro.properties";//properties.load(new FileInputStream(propertiesPath));//Java和Web项目查找properties文件,但不适用于文件路径中有空格//Properties properties = new Properties();//properties.load(DBUtils.class.getClassLoader().getResourceAsStream("db.properties"));String dbClassName = (String)properties.get("DBClassName");String dbUrl = (String)properties.get("DBURL");String dbUsername = (String)properties.get("DBUsername");String dbPassword = (String)properties.get("DBPassword");Class.forName(dbClassName);conn = DriverManager.getConnection(dbUrl, dbUsername, dbPassword);} catch (IOException | ClassNotFoundException | SQLException e) {e.printStackTrace();}}public static Connection getConn() {return conn;}}
util DBExecute 操作数据库
public class DBExecute {//万能查询方法，返回Map<Integer, Object>// Integer只是计数，Object为数据public static Map<Integer, Object> executeQuery(String sql, Object... args){Map<Integer, Object> map = new HashMap();int key = 0;try(PreparedStatement ps = DBConnection.getConn().prepareStatement(sql)) {for (int i = 0; i < args.length; i++) {ps.setObject(i + 1, args[i]);}ResultSet rs = ps.executeQuery();ResultSetMetaData metaData = rs.getMetaData();int columnCount = metaData.getColumnCount();while (rs.next()){for (int i = 1; i <= columnCount; i++) {map.put(key++, rs.getObject(i));}}} catch (SQLException e) {e.printStackTrace();}return map;}//查询方法，返回相应对象集合，受限很多，但是新手阶段的很常用，对于理解反射和数据库封装非常有帮助// 适用于任何表: select * from / select u_id,u_name,... from// 不适用于返回值与类属性无关的sql: 例如：select count(*)/sun(*)/min(*)等// 不适用于多表查询的sql: 例如：select id, name from a, b等public static <T> List<T> executeQuery(Class<T> tClass, String sql, Object... args){List<T> list = new ArrayList<>();try(PreparedStatement ps = DBConnection.getConn().prepareStatement(sql)) {for (int i = 0; i < args.length; i++) {ps.setObject(i + 1, args[i]);}ResultSet rs = ps.executeQuery();ResultSetMetaData rsmd = rs.getMetaData();Constructor<T> constructor = tClass.getConstructor();while (rs.next()){T t = constructor.newInstance();for (int i = 1; i <= rsmd.getColumnCount(); i++) {String columnName = rsmd.getColumnName(i);Field field = tClass.getDeclaredField(columnName);field.setAccessible(true);field.set(t, rs.getObject(columnName));}list.add(t);}} catch (SQLException | NoSuchMethodException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();} catch (InstantiationException e) {e.printStackTrace();} catch (InvocationTargetException e) {e.printStackTrace();} catch (NoSuchFieldException e) {e.printStackTrace();}return list;}//万能修改方法，返回受影响行数intpublic static int executeUpdate(String sql, Object... args){try(PreparedStatement ps = DBConnection.getConn().prepareStatement(sql)) {for (int i = 0; i < args.length; i++) {ps.setObject(i + 1, args[i]);}return ps.executeUpdate();} catch (SQLException e) {e.printStackTrace();}return -1;}}
Propertise
myPro.propertise 存放数据库的信息
DBClassName = com.mysql.cj.jdbc.DriverDBURL = jdbc:mysql://localhost:3306/mydatabaseDBUsername = rootDBPassword = root
Test
testDBExecute() 测试
public class Test {public static void main(String[] args) {testDBExecute();testDaoImpl();testService();}//就测测DBUtilpublic static void testDBExecute(){System.out.println("===========================================================================");System.out.println("+++++++Map<Integer, Object> executeQuery(String sql, Object... args)+++++++");Map<Integer, Object> map1 = DBExecute.executeQuery("select count(*) from address where a_id like '__'");Map<Integer, Object> map2 = DBExecute.executeQuery("select a_id, a_name from address where a_id like '__'");map1.forEach(new BiConsumer<Integer, Object>() {@Overridepublic void accept(Integer integer, Object o) {System.out.println("总数: " + o);}});map2.forEach(new BiConsumer<Integer, Object>() {@Overridepublic void accept(Integer integer, Object o) {System.out.println(o);}});System.out.println("===========================================================================");System.out.println("+++++List<T> executeQuery(Class<T> tClass, String sql, Object... args)+++++");List<Address> addresses1 = DBExecute.executeQuery(Address.class, "select * from address where a_id like concat(?,'__')", 21);for (Address address : addresses1) {System.out.println(address);}List<Address> addresses2 = DBExecute.executeQuery(Address.class, "select a_name, a_view_order from address where a_id like concat(?,'__')", 21);for (Address address : addresses2) {System.out.println(address);}System.out.println("===========================================================================");System.out.println("++++++++++++++++++++++++++DBExecute.executeUpdate++++++++++++++++++++++++++");DBExecute.executeUpdate("insert into address values(null, ?, ?, ?)", "佛山", 34, 12);DBExecute.executeUpdate("delete from address where a_view_order = ? and a_name = ?", 13, "佛山");DBExecute.executeUpdate("update address set a_id = ? where a_name = ?", 80, "佛山");}//想看看DBUtil怎么用在DAO中public static void testDaoImpl(){AddressDao addressDao = new AddressDaoImpl();List<Address> allBooks = addressDao.getAllBooks();for (Address book : allBooks) {System.out.println(book);}}//想看看DBUtil怎么用在Service中public static void testService(){AddressService addressService = new AddressService();List<Address> allBooks = addressService.getAllBooks();for (Address book : allBooks) {System.out.println(book);}}}
总结
优化了一点点
歇了～～有空再写注释
进我主页，免费下载源码（不知道怎么把资源链接放上来啊～～）
