Java开发中，常用工具封装

Java开发中，常用工具封装

JDBC工具

1、基于Druid

需要安装以下依赖

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.31</version>
</dependency>
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid</artifactId>
    <version>1.1.1</version>
</dependency>

jdbc.properties 【不能是jdbc.password这种，jdbc.url 并不是 Druid 支持的标准配置项名称，因此会导致配置解析失败。】

password=zhw521

# 连接池配置
initialSize=5
maxActive=20
maxWait=30000

# 其他配置
driverClassName=com.mysql.cj.jdbc.Driver

实现代码

import com.alibaba.druid.pool.DruidDataSourceFactory;
import javax.sql.DataSource;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;
public class JDBCUtil {
    private static final ThreadLocal<Connection> threadLocal = new ThreadLocal<>();
    private static final DataSource dataSource;

    //初始化连接池
    static {
        Properties properties = new Properties();
        InputStream resourceAsStream = JDBCUtil.class.getClassLoader().getResourceAsStream("jdbc.properties");
        try {
            properties.load(resourceAsStream);
            dataSource = DruidDataSourceFactory.createDataSource(properties);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    //向外提供连接池的方法
    public static DataSource getDataSource() {
        return dataSource;
    }

    //向外提供连接的方法
    public static Connection getConnection() throws SQLException {
        Connection connection = threadLocal.get();
        if (null == connection) {
            connection = dataSource.getConnection();
            threadLocal.set(connection);
        }
        return connection;
    }

    public static void closeConnection() {
        Connection connection = threadLocal.get();
        if (null != connection) {
            try {
                connection.setAutoCommit(true);
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
            threadLocal.remove();
        }
    }
}

BaseDao

代码实现

package com.zhw.schedule.dao;
import com.zhw.schedule.util.JDBCUtil;
import java.lang.reflect.Field;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class BaseDao {
    // 公共的查询方法  返回的是单个对象
    public <T> T baseQueryObject(String sql, Object... args) {
        T t = null;
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        try {
            connection = JDBCUtil.getConnection();
            preparedStatement = connection.prepareStatement(sql);
            for (int i = 0; i < args.length; i++) {
                preparedStatement.setObject(i + 1, args[i]);
            }
            resultSet = preparedStatement.executeQuery();
            if (resultSet.next()) {
                t = (T) resultSet.getObject(1);
            }
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            try {
                if (null != resultSet) {
                    resultSet.close();
                }
                if (null != preparedStatement) {
                    preparedStatement.close();
                }
            } catch (SQLException e) {
                throw new RuntimeException(e);
            }
            JDBCUtil.closeConnection();
        }
        return t;
    }

    // 公共的查询方法  返回的是对象的集合
    public <T> List<T> baseQuery(Class clazz, String sql, Object... args) {
        ArrayList<T> list = new ArrayList<>();
        ResultSet resultSet = null;
        PreparedStatement preparedStatement = null;
        try {
            Connection connection = JDBCUtil.getConnection();
            preparedStatement = connection.prepareStatement(sql);
            for (int i = 0; i < args.length; i++) {
                preparedStatement.setObject(i + 1, args[i]);
            }
            resultSet = preparedStatement.executeQuery();
            ResultSetMetaData metaData = resultSet.getMetaData();
            int columnCount = metaData.getColumnCount();
            while (resultSet.next()) {
                Object obj = clazz.getDeclaredConstructor().newInstance();
                for (int i = 1; i <= columnCount; i++) {
                    String columnName = metaData.getColumnLabel(i);
                    Object value = resultSet.getObject(columnName);
                    Field field = clazz.getDeclaredField(columnName);
                    field.setAccessible(true);
                    field.set(obj, value);
                }
                list.add((T) obj);
            }
        } catch (Exception e) {
            throw new RuntimeException(e);
        } finally {
            if (null != resultSet) {
                try {
                    resultSet.close();
                } catch (SQLException e) {
                    throw new RuntimeException(e);
                }
            }
            if (null != preparedStatement) {
                try {
                    preparedStatement.close();
                } catch (SQLException e) {
                    throw new RuntimeException(e);
                }
            }
            JDBCUtil.closeConnection();
        }
        return list;
    }

    // 通用的增删改方法
    public int baseUpdate(String sql, Object... args) {
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        int rows = 0;
        try {
            connection = JDBCUtil.getConnection();
            preparedStatement = connection.prepareStatement(sql);
            for (int i = 0; i < args.length; i++) {
                preparedStatement.setObject(i + 1, args[i]);
            }
            rows = preparedStatement.executeUpdate();
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            if (null != preparedStatement) {
                try {
                    preparedStatement.close();
                } catch (SQLException e) {
                    throw new RuntimeException(e);
                }
            }
            JDBCUtil.closeConnection();
        }
        return rows;
    }
}