使用DbUtils对JDBC封装实现面向实体查询

org.smart4j.chapter2.helper; import org.apache.commons.dbcp2.BasicDataSource; import org.apache.commons.dbutils.QueryRunner; import org.apache.commons.dbutils.handlers.BeanHandler; import org.apache.commons.dbutils.handlers.BeanListHandler; import org.apache.commons.dbutils.handlers.MapListHandler; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.smart4j.chapter2.util.CollectionUtil; import org.smart4j.chapter2.util.PropsUtil; import java.sql.Connection; import java.sql.SQLException; import java.util.ArrayList; import java.util.List; import java.util.Map; import java.util.Properties; /** * DbUtils 提供对 JDBC 的轻量级封装 * 通过 DbUtils 提供的 QueryRunner 对象可以面向实体（Entity）进行查询。 * 它的原理是：执行 SQL 语句并返回一个 ResultSet，随后通过反射去创建并初始化实体对象。 * Created by zhengbinMac on 2017/3/25. */ public class DatabaseHelper { private static final Logger LOGGER = LoggerFactory.getLogger(DatabaseHelper.class); // 线程连接 private static final ThreadLocal<Connection> CONNECTION_THREAD_LOCAL; // DbUtils private static final QueryRunner QUERY_RUNNER; // 线程池 private static final BasicDataSource DATA_SOURCE; static { CONNECTION_THREAD_LOCAL = new ThreadLocal<>(); QUERY_RUNNER = new QueryRunner(); Properties conf = PropsUtil.loadProps("config.properties"); // 设置连接池，使用 DBCP 来获取数据库连接 DATA_SOURCE = new BasicDataSource(); DATA_SOURCE.setDriverClassName(conf.getProperty("jdbc.driver")); DATA_SOURCE.setUrl(conf.getProperty("jdbc.url")); DATA_SOURCE.setUsername(conf.getProperty("jdbc.username")); DATA_SOURCE.setPassword(conf.getProperty("jdbc.password")); } /** * 获取数据库连接 */ public static Connection getConnection() { // 首先从 ThreadLocal 中获取 Connection connection = CONNECTION_THREAD_LOCAL.get(); // 若不存在，则创建一个新的 Connection，并最终将其放入 ThreadLocal 中 if (connection == null) { try { connection = DATA_SOURCE.getConnection(); } catch (SQLException e) { LOGGER.error("get connection failure", e); } finally { CONNECTION_THREAD_LOCAL.set(connection); } } return connection; } /** * 批量查询实体 */ public static <T> List<T> queryEntityList(Class<T> entityClass, String sql, Object... params) { List<T> entityList = null; try { Connection conn = getConnection(); entityList = QUERY_RUNNER.query(conn, sql, new BeanListHandler<T>(entityClass), params); } catch (SQLException e) { LOGGER.error("query entity list failure", e); } return entityList; } /** * 查询单个实体 */ public static <T> T queryEntity(Class<T> entityClass, String sql, Object... params) { T entity = null; try { Connection conn = getConnection(); entity = QUERY_RUNNER.query(conn, sql, new BeanHandler<T>(entityClass), params); } catch (SQLException e) { LOGGER.error("query entity failure", e); e.printStackTrace(); } return entity; } public static List<Map<String, Object>> executeQuery(String sql, Object... params) { List<Map<String, Object>> result = null; try { Connection conn = getConnection(); result = QUERY_RUNNER.query(conn, sql, new MapListHandler(), params); } catch (SQLException e) { LOGGER.error("query entity failure", e); e.printStackTrace(); } return result; } /** * 执行更新语句（update、insert 和 delete） */ public static int executeUpdate(String sql, Object... params) { int updateRows = 0; try { Connection conn = getConnection(); updateRows = QUERY_RUNNER.update(conn, sql, params); } catch (SQLException e) { LOGGER.error("execute update failure", e); e.printStackTrace(); } return updateRows; } /** * 插入实体 */ public static <T> boolean insertEntity(Class<T> entityClass, Map<String, Object> fieldMap) { if (CollectionUtil.isEmpty(fieldMap)) { LOGGER.error("can not insert entity: fieldMap is empty"); return false; } String sql = "INSERT INTO " + getTableName(entityClass); StringBuilder colums = new StringBuilder("("); StringBuilder values = new StringBuilder("("); // 插入实体的字段名，和字段值的占位符 for (String colum : fieldMap.keySet()) { colums.append(colum).append(", "); values.append("?, "); } colums.replace(colums.lastIndexOf(", "), colums.length(), ")"); values.replace(values.lastIndexOf(", "), values.length(), ")"); sql += colums + " VALUES " + values; // 插入实体的值 Object[] params = fieldMap.values().toArray(); return executeUpdate(sql, params) == 1; } /** * 更新实体 */ public static <T> boolean updateEntity(Class<T> entityClass, long id, Map<String, Object> fieldMap) { if (CollectionUtil.isEmpty(fieldMap)) { LOGGER.error("can not update entity: fieldMap is empty"); return false; } // 更具 fieldMap 拼接出更新 SQL 语句 String sql = "UPDATE " + getTableName(entityClass) + " SET "; StringBuilder columns = new StringBuilder(); // 更新实体的字段 for (String colums : fieldMap.keySet()) { columns.append(columns).append("=?, "); } // 去掉 SQL 最后一个 ‘, ‘ sql += columns.substring(0, columns.lastIndexOf(", ")) + " WHERE id=?"; // 更新实体的值 List<Object> paramList = new ArrayList<Object>(); paramList.addAll(fieldMap.values()); paramList.add(id); // 增加主键 id Object[] params = paramList.toArray(); return executeUpdate(sql, params) == 1; } /** * 删除实体 */ public static <T> boolean deleteEntity(Class<T> entityClass, long id) { String sql = "DELTE FROM " + getTableName(entityClass) + "WHERE id=?"; return executeUpdate(sql, id) == 1; } /** * 获取操作表的表名，即实体的类名 */ private static String getTableName(Class<?> entityClass) { return entityClass.getSimpleName(); } }

两个工具类

集合工具类：

package org.smart4j.chapter2.util;

import org.apache.commons.collections.MapUtils;

import java.util.Collection;
import java.util.Map;

/**
 * 集合工具类
 * 
 * Created by zhengbinMac on 2017/3/25.
 */
public class CollectionUtil {
    /**
     * 判断 Collection 是否为空
     */
    public static boolean isEmpty(Collection<?> collection) {
        return CollectionUtil.isEmpty(collection);
    }

    /**
     * 判断 Collection 是否为非空
     */
    public static boolean isNotEmpty(Collection<?> collection) {
        return !isEmpty(collection);
    }

    /**
     * 判断 Map 是否为空
     */
    public static boolean isEmpty(Map<?, ?> map) {
        return MapUtils.isEmpty(map);
    }

    /**
     * 判断 Map 是否为非空
     */
    public static boolean isNotEmpty(Map<?, ?> map) {
        return !isEmpty(map);
    }
}

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属性文件（properties）工具类：

package org.smart4j.chapter2.util;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

/**
 * 属性文件工具类
 * 
 * Created by zhengbinMac on 2017/3/25.
 */
public class PropsUtil {
    private static final Logger LOGGER = LoggerFactory.getLogger(PropsUtil.class);

    /**
     * 加载属性文件
     */
    public static Properties loadProps(String fileName) {
        Properties properties = null;
        InputStream is = null;
        try {
            is = Thread.currentThread().getContextClassLoader().getResourceAsStream(fileName);
            if (is == null) {
                throw new FileNotFoundException(fileName + "file is not found");
            }
            properties = new Properties();
            properties.load(is);
        } catch (IOException e) {
            LOGGER.error("load properties file failure", e);
        } finally {
            if (is != null) {
                try {
                    is.close();
                } catch (IOException e) {
                    LOGGER.error("close inputStream failure", e);
                }
            }
        }
        return properties;
    }

    /**
     * 获取字符型属性（默认值为空字符串）
     */
    public static String getString(Properties properties, String key) {
        return getString(properties, key, "");
    }

    /**
     * 获取字符型属性（可指定默认值）
     */
    public static String getString(Properties properties, String key, String defaultValue) {
        String value = defaultValue;
        if (properties.contains(key)) {
            value = properties.getProperty(key);
        }
        return value;
    }

    /**
     * 获取数值型属性（默认值为0）
     */
    public static int getInt(Properties properties, String key) {
        return getInt(properties, key, 0);
    }

    /**
     * 获取数值型属性（可指定默认值）
     */
    public static int getInt(Properties properties, String key, int defaultValue) {
        int value = defaultValue;
        if (properties.contains(key)) {
            value = CastUtil.castInt(properties.getProperty(key));
        }
        return value;
    }

    /**
     * 获取布尔型属性（默认值为 false）
     */
    public static boolean getBoolean(Properties properties, String key) {
        return getBoolean(properties, key, false);
    }

    /**
     * 获取布尔型属性（可指定默认值）
     */
    public static boolean getBoolean(Properties properties, String key, boolean defaultValue) {
        boolean value = defaultValue;
        if (properties.contains(key)) {
            value = CastUtil.castBoolean(properties.getProperty(key));
        }
        return value;
    }
}

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参考资料

[1] 架构探险, 第 2 章 - 为 Web 应用添加业务功能

使用DbUtils对JDBC封装实现面向实体查询

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