JDBCUtils如下：
package com.apesblog.jdbcutil1.util;
import java.io.InputStream;
import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Properties;
import java.util.Set;
import com.apesblog.jdbcutil1.bean.Order;
public class JDBCUtils {
private static Connection getConnection() throws Exception {
// 1.读取配置文件中的4个基本信息
InputStream is = ClassLoader.getSystemClassLoader().getResourceAsStream("jdbc.properties");
Properties pros = new Properties();
pros.load(is);
String user = pros.getProperty("user");
String password = pros.getProperty("password");
String url = pros.getProperty("url");
String driverClass = pros.getProperty("driverClass");
// 2.加载驱动
Class.forName(driverClass);
// 3.获取连接
Connection conn = DriverManager.getConnection(url, user, password);
return conn;
}
private static void closeResource(Connection conn, Statement ps) {
try {
if (ps != null)
ps.close();
} catch (SQLException e) {
e.printStackTrace();
}
try {
if (conn != null)
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
private static void closeResource(Connection conn, Statement ps, ResultSet rs) {
try {
if (ps != null)
ps.close();
} catch (SQLException e) {
e.printStackTrace();
}
try {
if (conn != null)
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
try {
if (rs != null)
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
public static void update(String sql, Object... args) {// sql中占位符的个数与可变形参的长度相同！
Connection conn = null;
PreparedStatement ps = null;
try {
// 1.获取数据库的连接
conn = JDBCUtils.getConnection();
// 2.预编译sql语句，返回PreparedStatement的实例
ps = conn.prepareStatement(sql);
// 3.填充占位符
for (int i = 0; i < args.length; i++) {
ps.setObject(i + 1, args[i]);// 小心参数声明错误！！
}
// 4.执行
ps.execute();
} catch (Exception e) {
e.printStackTrace();
} finally {
// 5.资源的关闭
JDBCUtils.closeResource(conn, ps);
}
}
public static <T> List<T> query(Class<T> clazz, String sql, Object... args) {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
try {
conn = JDBCUtils.getConnection();
ps = conn.prepareStatement(sql);
for (int i = 0; i < args.length; i++) {
ps.setObject(i + 1, args[i]);
}
rs = ps.executeQuery();
// 获取结果集的元数据 :ResultSetMetaData
ResultSetMetaData rsmd = rs.getMetaData();
// 通过ResultSetMetaData获取结果集中的列数
int columnCount = rsmd.getColumnCount();
// 创建集合对象
ArrayList<T> list = new ArrayList<T>();
while (rs.next()) {
T t = clazz.newInstance();
// 处理结果集一行数据中的每一个列:给t对象指定的属性赋值
for (int i = 0; i < columnCount; i++) {
// 获取列值
Object columValue = rs.getObject(i + 1);
// 获取每个列的列名
// String columnName = rsmd.getColumnName(i + 1);
String columnLabel = rsmd.getColumnLabel(i + 1);
// 给t对象指定的columnName属性，赋值为columValue：通过反射
Field field = clazz.getDeclaredField(columnLabel);
field.setAccessible(true);
field.set(t, columValue);
}
list.add(t);
}
return list;
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.closeResource(conn, ps, rs);
}
return null;
}
public static void updateDomain(String sql, Object object) {
Connection conn = null;
PreparedStatement ps = null;
Class<? extends Object> clazz = object.getClass();
Field[] fields = clazz.getDeclaredFields();
HashMap<Integer, String> hashMap = new HashMap<Integer, String>();
for (int i = 0; i < fields.length; i++) {
String lowerCase = fields[i].getName().toLowerCase();
int indexOf = sql.indexOf(lowerCase);
if (indexOf == -1)
continue;
hashMap.put(indexOf, fields[i].getName());
}
try {
// 1.获取数据库的连接
conn = JDBCUtils.getConnection();
// 2.预编译sql语句，返回PreparedStatement的实例
ps = conn.prepareStatement(sql);
// 3.填充占位符
int size = hashMap.size();
for (int i = 0; i < size; i++) {// --for() begin
Integer minKey = (Integer) getMinKey(hashMap);
String string = hashMap.get(minKey);
Field field = clazz.getDeclaredField(string);
field.setAccessible(true);
Object value = field.get(object);
if (value == null)
continue;
ps.setObject(i + 1, value);// 小心参数声明错误！！
hashMap.remove(minKey);
}
// 4.执行
ps.execute();
} catch (Exception e) {
e.printStackTrace();
} finally {
// 5.资源的关闭
JDBCUtils.closeResource(conn, ps);
}
}
public static <T> List<T> queryDomain(Class<T> clazz, String sql, Object object) {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
Class<? extends Object> objclazz = object.getClass();
Field[] fields = objclazz.getDeclaredFields();
HashMap<Integer, String> hashMap = new HashMap<Integer, String>();
for (int i = 0; i < fields.length; i++) {
String lowerCase = fields[i].getName().toLowerCase();
int indexOf;
if (sql.indexOf("from") == -1) {
indexOf = sql.substring(sql.indexOf("FROM")).indexOf(lowerCase);
} else {
indexOf = sql.substring(sql.indexOf("from")).indexOf(lowerCase);
}
if (indexOf == -1)
continue;
hashMap.put(indexOf, fields[i].getName());
}
try {
conn = JDBCUtils.getConnection();
ps = conn.prepareStatement(sql);
int size = hashMap.size();
for (int i = 0; i < size; i++) {// --for() begin
Integer minKey = (Integer) getMinKey(hashMap);
String string = hashMap.get(minKey);
Field field = clazz.getDeclaredField(string);
field.setAccessible(true);
Object value = field.get(object);
if (value == null)
continue;
ps.setObject(i + 1, value);// 小心参数声明错误！！
hashMap.remove(minKey);
}
rs = ps.executeQuery();
// 获取结果集的元数据 :ResultSetMetaData
ResultSetMetaData rsmd = rs.getMetaData();
// 通过ResultSetMetaData获取结果集中的列数
int columnCount = rsmd.getColumnCount();
// 创建集合对象
ArrayList<T> list = new ArrayList<T>();
while (rs.next()) {
T t = clazz.newInstance();
// 处理结果集一行数据中的每一个列:给t对象指定的属性赋值
for (int i = 0; i < columnCount; i++) {
// 获取列值
Object columValue = rs.getObject(i + 1);
// 获取每个列的列名
// String columnName = rsmd.getColumnName(i + 1);
String columnLabel = rsmd.getColumnLabel(i + 1);
// 给t对象指定的columnName属性，赋值为columValue：通过反射
Field field = clazz.getDeclaredField(columnLabel);
field.setAccessible(true);
field.set(t, columValue);
}
list.add(t);
}
return list;
} catch (Exception e) {
e.printStackTrace();
} finally {
JDBCUtils.closeResource(conn, ps, rs);
}
return null;
}
private static Object getMinKey(HashMap<Integer, String> hashMap) {
if (hashMap == null)
return null;
Set<Integer> set = hashMap.keySet();
Object[] obj = set.toArray();
Arrays.sort(obj);
return obj[0];
}
}
测试类如下：
package com.apesblog.jdbcutil1.util;
import java.util.List;
import org.junit.Test;
import org.junit.internal.requests.OrderingRequest;
import com.apesblog.jdbcutil1.bean.Customer;
import com.apesblog.jdbcutil1.bean.Order;
public class Test1 {
@Test
public void testUpdateDoamin() {
String sql = "delete from customers where id = ?";
Customer customer = new Customer();
customer.setId(4);
JDBCUtils.updateDomain(sql, customer);
sql = "update `order` set ordername = ? where orderid = ?";
Order order = new Order();
order.setOrderName("zzzz");
order.setOrderId(1);
JDBCUtils.updateDomain(sql, order);
}
@Test
public void testQueryDomain() {
String sql = "select id,name,email from customers where id < ?";
Customer customer = new Customer();
customer.setId(12);
List<Customer> list = JDBCUtils.queryDomain(Customer.class, sql, customer);
list.forEach(System.out::println);
String sql1 = "select orderid orderId,ordername orderName from `order`";
List<Order> orderList = JDBCUtils.queryDomain(Order.class, sql1, new Order());
orderList.forEach(System.out::println);
}
@Test
public void testUpdate() {
// String sql = "delete from customers where id = ?";
// update(sql,3);
String sql = "update `order` set ordername = ? where orderid = ?";
JDBCUtils.update(sql, "zys", "2");
}
@Test
public void testQuery() {
String sql = "select id,name,email from customers where id < ?";
List<Customer> list = JDBCUtils.query(Customer.class, sql, 12);
list.forEach(System.out::println);
String sql1 = "select orderid orderId,ordername orderName from `order`";
List<Order> orderList = JDBCUtils.query(Order.class, sql1);
orderList.forEach(System.out::println);
}
}
总结：
1.0
增删改没有结果集，封装成一个方法，但是传的是具体的值，不是domain，公司框架传的是domain，那是如何获取值得呢？
查询操作因为需要返回不同的domainList，所以需要传入domain.class
2.0
新增updateDomain通过反射获取属性
3.0
新增queryDomain，完成告一段落
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