Java实现关系型数据库工具类JdbcUtils系列九：通用DAO
一、创建对应数据库表的实体类
数据库表结构
CREATE TABLE `databaseInfo` (
`id` bigint(11) NOT NULL AUTO_INCREMENT COMMENT '自增id',
`database_name` varchar(100) NOT NULL COMMENT '数据库名称',
`table_name` varchar(100) NOT NULL COMMENT '表名',
`table_comment` varchar(300) DEFAULT NULL COMMENT '表的描述',
`table_rows` bigint(20) DEFAULT 0 COMMENT '表的行数',
`column_key` varchar(100) NOT NULL COMMENT '表的主键',
`create_time` datetime DEFAULT NULL COMMENT '创建时间',
`update_time` datetime DEFAULT NULL COMMENT '更新时间',
PRIMARY KEY (`id`),
UNIQUE KEY `uniq_databasename_tablename` (`database_name`,`table_name`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8mb4 COMMENT='源数据库表信息';
根据表结构创建对应的实体类
import lombok.*;
import java.io.Serializable;
/**
* <p>
* 源数据库表信息
* </p>
*
* @author fei.yang4
* @since 2021-11-03
*/
@Data
@AllArgsConstructor
@EqualsAndHashCode(callSuper = false)
@ToString
@NoArgsConstructor
public class DatabaseInfo implements Serializable {
/**
* 数据库名称
*/
private String databaseName;
/**
* 数据表全称,格式：dbName.tableName
*/
private String tableName;
/**
* 表的描述
*/
private String tableComment;
/**
* 表的行数
*/
private Long tableRows;
/**
* 表的主键
*/
private String tableKey;
}
二、数据库连接池Druid工具类
import com.alibaba.druid.pool.DruidDataSourceFactory;
import org.apache.commons.beanutils.PropertyUtils;
import javax.sql.DataSource;
import java.io.IOException;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;
public class JdbcUtils {
private static DataSource ds = null;
static {
try {
Properties props = new Properties();
props.load(JdbcUtils.class.getClassLoader().getResourceAsStream("druid.properties"));
ds = DruidDataSourceFactory.createDataSource(props);
} catch (Exception e) {
throw new RuntimeException("读取配置文件异常", e);
}
}
//Druid连接池
public static Connection getDruidConnection() throws Exception {
Connection conn = null;
conn = ds.getConnection();
return conn;
}
public static void release(Connection conn) throws SQLException {
if(conn != null) conn.close();
}
public static void release(Connection conn, PreparedStatement ps) throws SQLException {
if(ps!=null) ps.close();
if(conn!=null) conn.close();
}
public static void release(Connection conn, PreparedStatement ps, java.sql.ResultSet rs) throws SQLException {
if(rs!=null) rs.close();
if(ps!=null) ps.close();
if(conn!=null) conn.close();
}
}
三、DAO类
import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;
public interface DAO<T> {
/**
* 获取特殊值。如：最大值，总数等。
* @param conn
* @param sql
* @param params
* @return
*/
public Object getValue(Connection conn,String sql,Object ... params) throws SQLException;
/**
* 查询多个对象并存入List<T>中
* @param conn
* @param sql
* @param params
* @return
*/
public List<T> getList(Connection conn,String sql,Object ... params) throws SQLException;
/**
* 查询单个对象
* @param conn
* @param sql
* @param params
* @return
*/
public T get(Connection conn,String sql,Object ... params) throws SQLException;
/**
* 考虑事务，通用的增删改
* @param conn
* @param sql
* @param params
* @return
*/
public int update(Connection conn,String sql,Object ... params) throws SQLException;
}
四、BaseDAO
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.ScalarHandler;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;
public abstract class BaseDAO<T> implements DAO<T> {
Class<T> clazz = null;
public BaseDAO(){
//1.获取带范型父类的类型
Type type = this.getClass().getGenericSuperclass();
//2.参数化类型
ParameterizedType pt = (ParameterizedType) type;
//3.获取真实参数
Type[] types = pt.getActualTypeArguments();
clazz = (Class<T>) types[0];
}
private QueryRunner qr = new QueryRunner();
@Override
public Object getValue(Connection conn, String sql, Object... params) throws SQLException {
return qr.query(conn,sql,new ScalarHandler(),params);
}
@Override
public List<T> getList(Connection conn, String sql,Object... params) throws SQLException {
return qr.query(conn,sql,new BeanListHandler<>(clazz),params);
}
@Override
public T get(Connection conn, String sql, Object... params) throws SQLException {
return qr.query(conn,sql,new BeanHandler<>(clazz),params);
}
@Override
public int update(Connection conn, String sql, Object... params) throws SQLException {
return qr.update(conn,sql,params);
}
}
五、DatabaseInfoDao
public class DatabaseInfoDao extends BaseDAO<DatabaseInfo> {
}
六、通用DAO测试类
import com.bigdata.plus.Entity.DatabaseInfo;
import com.bigdata.plus.Entity.DatabaseInfoDao;
import org.junit.Test;
import java.io.IOException;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;
public class DAOTest {
@Test
public void test1() throws SQLException, IOException, ClassNotFoundException {
Connection conn = null;
try{
conn = JdbcUtils.getConnection();
DatabaseInfoDao databaseInfoDao = new DatabaseInfoDao();
String sql = "select t.TABLE_SCHEMA as databaseName,CONCAT_WS('.',t.TABLE_SCHEMA,t" +
".TABLE_NAME)" +
" as " +
"tableName,t.TABLE_COMMENT as tableComment,t.TABLE_ROWS as tableRows,k.COLUMN_NAME as " +
"tableKey\n" +
"from INFORMATION_SCHEMA.TABLES as t\n" +
"inner join INFORMATION_SCHEMA.KEY_COLUMN_USAGE as k\n" +
"on k.TABLE_NAME=t.TABLE_NAME and CONSTRAINT_NAME = 'PRIMARY' and t.TABLE_SCHEMA=?";
Object[] params = {
"dw"};
DatabaseInfo databaseInfo = databaseInfoDao.get(conn, sql, params);
System.out.println(databaseInfo);
} catch (SQLException e){
e.printStackTrace();
}finally {
JdbcUtils.release(conn,null,null);
}
}
@Test
public void test2() throws SQLException, IOException, ClassNotFoundException {
Connection conn = null;
try{
conn = JdbcUtils.getConnection();
DatabaseInfoDao databaseInfoDao = new DatabaseInfoDao();
String sql = "select t.TABLE_SCHEMA as databaseName,CONCAT_WS('.',t.TABLE_SCHEMA,t" +
".TABLE_NAME)" +
" as " +
"tableName,t.TABLE_COMMENT as tableComment,t.TABLE_ROWS as tableRows,k.COLUMN_NAME as " +
"tableKey\n" +
"from INFORMATION_SCHEMA.TABLES as t\n" +
"inner join INFORMATION_SCHEMA.KEY_COLUMN_USAGE as k\n" +
"on k.TABLE_NAME=t.TABLE_NAME and CONSTRAINT_NAME = 'PRIMARY' and t.TABLE_SCHEMA=?";
Object[] params = {
"dw"};
List<DatabaseInfo> list = databaseInfoDao.getList(conn, sql, params);
for(DatabaseInfo databaseInfo : list){
System.out.println(list);
}
} catch (SQLException e){
e.printStackTrace();
}finally {
JdbcUtils.release(conn,null,null);
}
}
}
