JDBC的DML增删改查的代码重构设计（上）

1 设计商品对象

public class Product {private Long id;private String productName;private String brand;private String supplier;private BigDecimal salePrice;private BigDecimal costPrice;private Double cutoff;private Long dir_id;//分类编号public Long getId() {return id;}public String getProductName() {return productName;}public String getBrand() {return brand;}public String getSupplier() {return supplier;}public BigDecimal getSalePrice() {return salePrice;}public BigDecimal getCostPrice() {return costPrice;}public Double getCutoff() {return cutoff;}public Long getDir_id() {return dir_id;}public void setId(Long id) {this.id = id;}public void setProductName(String productName) {this.productName = productName;}public void setBrand(String brand) {this.brand = brand;}public void setSupplier(String supplier) {this.supplier = supplier;}public void setSalePrice(BigDecimal salePrice) {this.salePrice = salePrice;}public void setCostPrice(BigDecimal costPrice) {this.costPrice = costPrice;}public void setCutoff(Double cutoff) {this.cutoff = cutoff;}public void setDir_id(Long dir_id) {this.dir_id = dir_id;}@Overridepublic String toString() {return "Product [id=" + id + ", productName=" + productName + ", brand=" + brand + ", suppliet=" + supplier+ ", salePrice=" + salePrice + ", costPrice=" + costPrice + ", cutoff=" + cutoff + ", dir_id=" + dir_id+ "]";}
}

2 设计实现DAO接口

import java.util.List;import cn.itsource._05_.shopping.domain.Product;public interface IProductDAO {void save(Product pro);void delete(Long id);void update(Product pro);//long id 包装进去productProduct get(Long id);List<Product> list();}

3 使用Statment增删改查的实现类

public class ProductDAOImpl implements IProductDAO {public void save(Product pro) {Connection conn = null;Statement st = null;try {conn = JdbcUtil.INSTANCE.getConn();st = conn.createStatement();//使用StringBuilder可以减少性能的损耗，不然每次都要创建一个对象然后更改数据！StringBuilder sql = new StringBuilder();sql.append("insert into product (productName,brand,supplier,salePrice,costPrice,cutoff,dir_id ) values (");sql.append("'").append(pro.getProductName()).append("'").append(",");sql.append("'").append(pro.getBrand()).append("'").append(",");sql.append("'").append(pro.getSupplier()).append("'").append(",");sql.append("'").append(pro.getSalePrice()).append("'").append(",");sql.append("'").append(pro.getCostPrice()).append("'").append(",");sql.append("'").append(pro.getCutoff()).append("'").append(",");sql.append("'").append(pro.getDir_id()).append("'");sql.append(")");st.executeUpdate(sql.toString());} catch (Exception e) {e.printStackTrace();} finally {JdbcUtil.INSTANCE.close(conn, st, null);}}public void delete(Long id) {Connection conn = null;Statement st = null;try {conn = JdbcUtil.INSTANCE.getConn();st = conn.createStatement();String sql = "delete from product where id = " + id;st.executeUpdate(sql);} catch (Exception e) {e.printStackTrace();} finally {JdbcUtil.INSTANCE.close(conn, st, null);}}public void update(Product pro) {Connection conn = null;Statement st = null;try {conn = JdbcUtil.INSTANCE.getConn();st = conn.createStatement();StringBuilder sql = new StringBuilder();sql.append("update product set ");sql.append("productName = ").append("'").append(pro.getProductName()).append("',");sql.append("brand =").append("'").append(pro.getBrand()).append("',");sql.append("supplier =").append("'").append(pro.getSupplier()).append("',");sql.append("salePrice =").append(pro.getSalePrice()).append(",");sql.append("costPrice =").append(pro.getCostPrice()).append(",");sql.append("cutoff =").append(pro.getCutoff()).append(",");sql.append("dir_id =").append(pro.getDir_id());sql.append(" where id = ").append(pro.getId());st.executeUpdate(sql.toString());} catch (Exception e) {e.printStackTrace();} finally {JdbcUtil.INSTANCE.close(conn, st, null);}}public Product get(Long id) {Connection conn = null;Statement st = null;ResultSet rs = null;try {conn = JdbcUtil.INSTANCE.getConn();st = conn.createStatement();String sql = "select * from product where id = " + id;rs = st.executeQuery(sql);if (rs.next()) {Product pro = new Product();//把一行数据中的，每一列的值，存储到对象的属性中pro.setId(rs.getLong("id"));pro.setProductName(rs.getString("productName"));pro.setBrand(rs.getString("brand"));pro.setSupplier(rs.getString("supplier"));pro.setSalePrice(rs.getBigDecimal("salePrice"));pro.setCostPrice(rs.getBigDecimal("costPrice"));pro.setCutoff(rs.getDouble("cutoff"));pro.setDir_id(rs.getLong("dir_id"));return pro;}} catch (Exception e) {e.printStackTrace();} finally {JdbcUtil.INSTANCE.close(conn, st, rs);}return null;}public List<Product> list() {List<Product> list = new ArrayList<Product>();Connection conn = null;Statement st = null;ResultSet rs = null;try {conn = JdbcUtil.INSTANCE.getConn();st = conn.createStatement();String sql = "select * from product";rs = st.executeQuery(sql);while (rs.next()) {//把当前的数据，封装成一个Product对象Product pro = new Product();list.add(pro);//把一行数据中的，每一列的值，存储到对象的属性中pro.setId(rs.getLong("id"));pro.setProductName(rs.getString("productName"));pro.setBrand(rs.getString("brand"));pro.setSupplier(rs.getString("supplier"));pro.setSalePrice(rs.getBigDecimal("salePrice"));pro.setCostPrice(rs.getBigDecimal("costPrice"));pro.setCutoff(rs.getDouble("cutoff"));pro.setDir_id(rs.getLong("dir_id"));}} catch (Exception e) {e.printStackTrace();} finally {JdbcUtil.INSTANCE.close(conn, st, rs);}return list;}
}

4 使用PreparedStatment增删改查的实现类

public class ProductDAOpreImpl implements IProductDAO {public void save(Product pro) {Connection conn = null;PreparedStatement ps = null;try {conn = JdbcUtil.INSTANCE.getConn();String sql = "insert into product (productName,brand,supplier,salePrice,costPrice,cutoff,dir_id ) values (?,?,?,?,?,?,?)";ps = conn.prepareStatement(sql);ps.setString(1, pro.getProductName());ps.setString(2, pro.getBrand());ps.setString(3, pro.getSupplier());ps.setBigDecimal(4, pro.getSalePrice());ps.setBigDecimal(5, pro.getCostPrice());ps.setDouble(6, pro.getCutoff());ps.setLong(7, pro.getDir_id());ps.executeUpdate();} catch (Exception e) {e.printStackTrace();} finally {JdbcUtil.INSTANCE.close(conn, ps, null);}}public void delete(Long id) {Connection conn = null;PreparedStatement ps = null;try {conn = JdbcUtil.INSTANCE.getConn();String sql = "delete from product where id = ?";ps = conn.prepareStatement(sql);ps.setLong(1, id);ps.executeUpdate();} catch (Exception e) {e.printStackTrace();} finally {JdbcUtil.INSTANCE.close(conn, ps, null);}}public void update(Product pro) {Connection conn = null;PreparedStatement ps = null;try {conn = JdbcUtil.INSTANCE.getConn();String sql = "UPDATE product SET productName = ?, brand = ?, supplier = ?, salePrice = ?, costPrice = ?, cutoff = ?, dir_id = ?  WHERE id = ?";ps = conn.prepareStatement(sql );ps.setString(1, pro.getProductName());ps.setString(2, pro.getBrand());ps.setString(3, pro.getSupplier());ps.setBigDecimal(4, pro.getSalePrice());ps.setBigDecimal(5, pro.getCostPrice());ps.setDouble(6, pro.getCutoff());ps.setLong(7, pro.getDir_id());ps.setLong(8,pro.getId());ps.executeUpdate();} catch (Exception e) {e.printStackTrace();} finally {JdbcUtil.INSTANCE.close(conn, ps, null);}}public Product get(Long id) {Connection conn = null;PreparedStatement ps = null;ResultSet rs = null;try {conn = JdbcUtil.INSTANCE.getConn();String sql = "select * from product where id = ?";ps = conn.prepareStatement(sql);ps.setLong(1, id);rs = ps.executeQuery();if (rs.next()) {Product pro = new Product();pro.setId(rs.getLong("id"));pro.setProductName(rs.getString("productName"));pro.setBrand(rs.getString("brand"));pro.setSupplier(rs.getString("supplier"));pro.setSalePrice(rs.getBigDecimal("salePrice"));pro.setCostPrice(rs.getBigDecimal("costPrice"));pro.setCutoff(rs.getDouble("cutoff"));pro.setDir_id(rs.getLong("dir_id"));return pro;}} catch (Exception e) {e.printStackTrace();} finally {JdbcUtil.INSTANCE.close(conn, ps, rs);}return null;}public List<Product> list() {List<Product> list = new ArrayList<>();Connection conn = null;PreparedStatement ps = null;ResultSet rs = null;try {conn = JdbcUtil.INSTANCE.getConn();String sql = "SELECT * FROM product";ps = conn.prepareStatement(sql);rs = ps.executeQuery();while (rs.next()) {Product pro = new Product();list.add(pro);pro.setId(rs.getLong("id"));pro.setProductName(rs.getString("productName"));pro.setBrand(rs.getString("brand"));pro.setSupplier(rs.getString("supplier"));pro.setSalePrice(rs.getBigDecimal("salePrice"));pro.setCostPrice(rs.getBigDecimal("costPrice"));pro.setCutoff(rs.getDouble("cutoff"));pro.setDir_id(rs.getLong("dir_id"));}} catch (Exception e) {e.printStackTrace();} finally {JdbcUtil.INSTANCE.close(conn, ps, rs);}return list;}
}

5 测试实现类

public class ProductDAOTest {private IProductDAO dao = new ProductDAOImpl();@Testpublic void testSave() {Product pro = new Product();pro.setProductName("iphone8s");pro.setBrand("apple");pro.setSupplier("苹果公司");pro.setSalePrice(new BigDecimal("7000"));pro.setCostPrice(new BigDecimal("2000"));pro.setCutoff(0.9);pro.setDir_id(3L);pro.setId(4L);dao.save(pro);}@Testpublic void testDelete() {dao.delete(6L);}@Testpublic void testUpdate() {Product pro = new Product();pro.setProductName("iphone6s");pro.setBrand("apple2");pro.setSupplier("苹果公司2");pro.setSalePrice(new BigDecimal("6000"));pro.setCostPrice(new BigDecimal("1000"));pro.setCutoff(0.8);pro.setDir_id(5L);pro.setId(5L);dao.update(pro);}@Testpublic void testGet() {Product pro = dao.get(10L);System.out.println(pro);}@Testpublic void testList() {List<Product> list = dao.list();for (Product p : list) {System.out.println(p);}}
}

6 代码重构JdbcUtil类的设计

public enum JdbcUtil {INSTANCE;private static Properties p = new Properties();//只需要注册一次驱动即可，没必要每次都注册，放到jdbcutil类的静态代码块中（当字节码被加载进jvm，就会执行）static {try {//从classpath的根路径去加载db.properties文件InputStream inStream = Thread.currentThread().getContextClassLoader().getResourceAsStream("db.properties");p.load(inStream);Class.forName(p.getProperty("driverClassName"));} catch (Exception e) {e.printStackTrace();}}/*** 创建connection对象* @return*/public Connection getConn() {try {return DriverManager.getConnection(p.getProperty("url"), p.getProperty("usename"),p.getProperty("password"));} catch (Exception e) {e.printStackTrace();}return null;}public void close(Connection conn, Statement st, ResultSet rs) {try {if (rs != null) {rs.close();}} catch (Exception e) {e.printStackTrace();} finally {try {if (st != null) {st.close();}} catch (Exception e) {e.printStackTrace();} finally {try {if (conn != null) {conn.close();}} catch (Exception e) {e.printStackTrace();}}}}
}

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