扩展c3p0写的通用数据库操作工具类（使用泛型方法）

package com.syx.utils;

import com.mchange.v2.c3p0.DataSources;
import com.syx.annotation.ID;
import com.syx.entity.User;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import javax.sql.DataSource;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class DBUtil {
    //数据源
    private static DataSource dataSource = null;
    //queryRunner对象
    private static QueryRunner queryRunner = null;
    //数据库的配置文件
    private static String dbconfig = "dbconfig.properties";

    /**
     * 初始化数据源
     */
    static {
        try {
            dataSource = DataSources.unpooledDataSource(PropertiesUtil.propertyValue(dbconfig, "jdbc.url"),
                    PropertiesUtil.propertyValue(dbconfig, "jdbc.user"),
                    PropertiesUtil.propertyValue(dbconfig, "jdbc.password"));
        } catch (SQLException e) {
            e.printStackTrace();
        }

    }

    /**
     * queryRunner对象（用户可以自己直接调用queryRunner种的方法）
     *
     * @return
     */
    public static QueryRunner queryRunner() {
        if (queryRunner == null) {
            queryRunner = new QueryRunner(dataSource);
            return queryRunner;
        }
        return queryRunner;
    }


    /**
     * 新增一条记录
     * @param t
     * @param <T>
     * @return
     */
    public static <T> int insert(T t) {
        queryRunner();
        Class<?> clazz = t.getClass();
        //sql的参数
        Object[] params  = getParams(clazz,t);
        //sql
        String sql = insertSql(clazz);

        try {
            return queryRunner.update(sql, params);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return 0;
    }

    /**
     * 获取get方法的值（用于为insert语句的?赋值）
     * @param clazz
     * @param t
     * @param <T>
     * @return
     */
    private static <T> Object[] getParams(Class<?> clazz,T t) {
        Method[] methods = clazz.getDeclaredMethods();
        ArrayList<Object> ls = new ArrayList<>();
        for (Method method : methods) {
            try {
                if(method.getName().contains("get")){
                    Object param = method.invoke(t);
                    ls.add(param);
                }
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            } catch (InvocationTargetException e) {
                e.printStackTrace();
            }
        }
        return ls.toArray();
    }


    /**
     * 拼接插入sql
     *
     * @param t
     * @param <T>
     * @return
     */
    private static <T> String insertSql(Class<T> t) {
        //表名
        String tableName = t.getSimpleName();
        StringBuffer sql = new StringBuffer("insert into " + tableName + "(");
        Field[] fields = t.getDeclaredFields();
        for (int i = 0; i < fields.length; i++) {
            if (i < fields.length - 1) {
                sql.append(fields[i].getName() + ",");
            } else {
                sql.append(fields[i].getName() + ")");
            }
        }
        sql.append(" values (");
        //添加问号
        for (int i = 0; i < fields.length; i++) {
            if (i < fields.length - 1) {
                sql.append("?,");
            } else {
                sql.append("?)");
            }
        }
        return sql.toString();
    }


    /**
     * 根据id查询一条记录
     *
     * @param t
     * @param id
     * @param <T>
     * @return
     */
    public static <T> T find(Class<T> t, String id) {
        queryRunner();
        //拼接sql
        String sql = querySql(t, false);
        try {
            return queryRunner.query(sql, new BeanHandler<>(t), id);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }


    /**
     * 查询所有
     * @param t
     * @param <T>
     * @return
     */
    public static <T> List<T> findAll(Class<T> t) {
        queryRunner();
        //拼接sql
        String sql = querySql(t, true);
        try {
            return queryRunner.query(sql, new BeanListHandler<>(t));
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * 拼接查询sql
     *
     * @param t
     * @param flag
     * @param <T>
     * @return
     */
    private static <T> String querySql(Class<T> t, boolean flag) {
        String tableName = t.getSimpleName();
        //查询所有
        if (flag) {
            String sql = "select * from " + tableName;
            return sql;
        }
        //获取所有的字段
        Field[] fields = t.getDeclaredFields();
        String id = "";
        for (Field field : fields) {
            if (field.isAnnotationPresent(ID.class)) {
                id = field.getName();
            }

        }
        String sql = "select * from " + tableName + " where " + id + " = ?";
        return sql;
    }

    public static void main(String[] args) {
//        List<User> all = findAll(User.class);
//        all.forEach(System.out::println);
//        User user = find(User.class, "1");
//        System.out.println(user);

        User user = new User();

        user.setId(7);
        user.setSex("女");

        user.setUsername("zyz");
        insert(user);
    }
}

本文地址：https://blog.csdn.net/weixin_42304484/article/details/112210858