【Java Web】DbUtils工具类 —— 简单封装JDBC通用增删改查方法
DbUtils工具类 —— 简单封装JDBC通用增删改查方法
- db.properties
- DbUtils.java
- ReflectionUtils.java
- 测试效果
- 参考资料
对jdbc进行了简单的封装，用到了java泛型和java 反射还有方法可变参数，增删改查执行完毕后自动关闭连接释放资源（以前经常忘记，导致服务器宕机），理论上任何项目都可以使用，有兴趣的朋友可以试试。
db.properties
数据库配置文件
# MySQL地址
url=jdbc:mysql://localhost:3306/web
# MySQL用户名
username=root
# MySQL密码
password=root
# MySQL驱动
driver=com.mysql.jdbc.Driver
DbUtils.java
数据库工具类
package utils;
import java.io.InputStream;
import java.sql.*;
import java.util.*;
/**
* MySQL工具类
*
* @author hui
* @date 2020/7/17 15:20
*/
public class DbUtils {
/**
* 获取数据库连接
*
* @return connection对象
*/
public static Connection getConnection() {
Connection connection = null;
Properties properties = new Properties();
InputStream in = DbUtils.class.getClassLoader().getResourceAsStream("db.properties");
try {
properties.load(in);
String url = properties.get("url").toString();
String username = properties.get("username").toString();
String password = properties.get("password").toString();
String driver = properties.get("driver").toString();
Class.forName(driver);
connection = DriverManager.getConnection(url, username, password);
} catch (Exception e) {
e.printStackTrace();
}
return connection;
}
/**
* 关闭数据库连接
*
* @param connection connection对象
* @param preparedStatement preparedStatement对象
* @param resultSet resultSet对象
*/
public static void release(Connection connection, PreparedStatement preparedStatement, ResultSet resultSet) {
try {
if (resultSet != null) {
resultSet.close();
}
if (preparedStatement != null) {
preparedStatement.close();
}
if (connection != null) {
connection.close();
}
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* 通用查询
*
* @param classes 类
* @param sql sql语句
* @param args 查询参数
* @param 泛型
* @return 泛型对象
*/
public static <T> T query(Class<T> classes, String sql, Object... args) {
T object = null;
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
ResultSetMetaData resultSetMetaData;
try {
connection = DbUtils.getConnection();
preparedStatement = connection.prepareStatement(sql);
for (int i = 0; i < args.length; i++) {
preparedStatement.setObject(i + 1, args[i]);
}
resultSet = preparedStatement.executeQuery();
resultSetMetaData = resultSet.getMetaData();
Map<String, Object> map = new HashMap<>(16);
if (resultSet.next()) {
for (int i = 0; i < resultSetMetaData.getColumnCount(); i++) {
String columnname = resultSetMetaData.getColumnLabel(i + 1);
Object obj = resultSet.getObject(i + 1);
map.put(columnname, obj);
}
}
if (map.size() > 0) {
object = classes.newInstance();
for (Map.Entry<String, Object> entry : map.entrySet()) {
String fieldName = entry.getKey();
Object value = entry.getValue();
ReflectionUtils.setFieldValue(object, fieldName, value);
}
}
} catch (Exception e) {
e.printStackTrace();
} finally {
DbUtils.release(connection, preparedStatement, resultSet);
}
return object;
}
/**
* 通用集合查询
*
* @param classes 类
* @param sql sql语句
* @param args 查询参数
* @param 泛型
* @return 泛型集合
*/
public static <T> List<T> list(Class<T> classes, String sql, Object... args) {
List<T> objects = new ArrayList<>();
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
ResultSetMetaData resultSetMetaData;
try {
connection = DbUtils.getConnection();
preparedStatement = connection.prepareStatement(sql);
for (int i = 0; i < args.length; i++) {
preparedStatement.setObject(i + 1, args[i]);
}
resultSet = preparedStatement.executeQuery();
resultSetMetaData = resultSet.getMetaData();
Map<String, Object> map = new HashMap<>(16);
while (resultSet.next()) {
T object = null;
for (int i = 0; i < resultSetMetaData.getColumnCount(); i++) {
String columnname = resultSetMetaData.getColumnLabel(i + 1);
Object obj = resultSet.getObject(i + 1);
map.put(columnname, obj);
}
if (map.size() > 0) {
object = classes.newInstance();
for (Map.Entry<String, Object> entry : map.entrySet()) {
String fieldName = entry.getKey();
Object value = entry.getValue();
ReflectionUtils.setFieldValue(object, fieldName, value);
}
}
objects.add(object);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
DbUtils.release(connection, preparedStatement, resultSet);
}
return objects;
}
/**
* 通用插入
*
* @param sql sql语句
* @param args 查询参数
* @return ture/fasle
*/
public static boolean save(String sql, Object... args) {
boolean state = true;
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try {
connection = DbUtils.getConnection();
preparedStatement = connection.prepareStatement(sql);
for (int i = 0; i < args.length; i++) {
preparedStatement.setObject(i + 1, args[i]);
}
preparedStatement.execute();
} catch (Exception e) {
state = false;
e.printStackTrace();
} finally {
DbUtils.release(connection, preparedStatement, resultSet);
}
return state;
}
/**
* 通用删除
*
* @param sql sql语句
* @param args 查询参数
* @return ture/fasle
*/
public static boolean remove(String sql, Object... args) {
boolean state = true;
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try {
connection = DbUtils.getConnection();
preparedStatement = connection.prepareStatement(sql);
for (int i = 0; i < args.length; i++) {
preparedStatement.setObject(i + 1, args[i]);
}
preparedStatement.execute();
} catch (Exception e) {
state = false;
e.printStackTrace();
} finally {
DbUtils.release(connection, preparedStatement, resultSet);
}
return state;
}
/**
* 通用更新
*
* @param sql sql语句
* @param args 查询参数
* @return ture/fasle
*/
public static boolean update(String sql, Object... args) {
boolean state = true;
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try {
connection = DbUtils.getConnection();
preparedStatement = connection.prepareStatement(sql);
for (int i = 0; i < args.length; i++) {
preparedStatement.setObject(i + 1, args[i]);
}
preparedStatement.execute();
} catch (Exception e) {
state = false;
e.printStackTrace();
} finally {
DbUtils.release(connection, preparedStatement, resultSet);
}
return state;
}
}
ReflectionUtils.java
反射工具类
package utils;
import java.lang.reflect.Field;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
/**
* @author hui
* @date 2020/7/17 15:50
*/
public class ReflectionUtils {
/**
* 通过反射，获得Class定义中声明的父类的泛型参数类型
*
* @param clazz 类
* @return
*/
public static <T> Class<T> getSuperGenericType(Class clazz) {
return getSuperClassGenricType(clazz, 0);
}
/**
* 通过反射, 获得定义 Class 时声明的父类的泛型参数的类型
*
* @param clazz 类
* @param index 索引
* @return 类
*/
public static Class getSuperClassGenricType(Class clazz, int index) {
Type genType = clazz.getSuperclass();
if (!(genType instanceof ParameterizedType)) {
return Object.class;
}
Type[] params = ((ParameterizedType) genType).getActualTypeArguments();
if (index >= params.length || index < 0) {
return Object.class;
}
if (!(params[index] instanceof Class)) {
return Object.class;
}
return (Class) params[index];
}
/**
* 循环向上转型, 获取对象的 DeclaredMethod
*
* @param object 类
* @param fieldName 属性
* @return 属性
*/
public static Field getDeclaredField(Object object, String fieldName) {
Field field;
Class<?> clazz = object.getClass();
for (; clazz != Object.class; clazz = clazz.getSuperclass()) {
try {
field = clazz.getDeclaredField(fieldName);
return field;
} catch (Exception e) {
e.printStackTrace();
}
}
return null;
}
/**
* 设置参数
*
* @param object 对象
* @param fieldName 属性
* @param value 值
*/
public static void setFieldValue(Object object, String fieldName, Object value) {
Field field = getDeclaredField(object, fieldName);
assert field != null;
field.setAccessible(true);
try {
field.set(object, value);
} catch (IllegalArgumentException | IllegalAccessException e) {
e.printStackTrace();
}
}
/**
* 获取参数
*
* @param object 对象
* @param fieldName 属性
* @return 值
*/
public static Object getFieldValue(Object object, String fieldName) {
Field field = getDeclaredField(object, fieldName);
assert field != null;
field.setAccessible(true);
try {
return field.get(object);
} catch (IllegalArgumentException | IllegalAccessException e) {
e.printStackTrace();
}
return null;
}
}
测试效果
参考资料
https://blog.csdn.net/lw277232240/article/details/80465859
https://blog.csdn.net/Geek_sun/article/details/81296214