Java实现关系型数据库工具类JdbcUtils系列六：ORM对象关系映射查询多个对象存入List集合
- 一、ORM对象关系映射
- 二、表结构和表对应的实体类
- 三、查询多个对象存入List集合ORM映射到实体类中
- 四、测试类
- 五、完整代码
- 六、运行测试类输出如下所示
一、ORM对象关系映射
- 数据库中的一个表：Java中的一个类
- 数据库中的一个字段：Java中的一个属性
- 数据表中的一条数据：Java中的一个对象
二、表结构和表对应的实体类
CREATE TABLE `databaseInfo` (
`id` int(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',
`table_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';
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.EqualsAndHashCode;
import lombok.ToString;
import java.io.Serializable;
@Data
@AllArgsConstructor
@EqualsAndHashCode(callSuper = false)
@ToString
public class DatabaseInfo implements Serializable {
private String databaseName;
private String tableName;
private String tableComment;
private Long tableRows;
private String tableKey;
}
三、查询多个对象存入List集合ORM映射到实体类中
public List getList() throws SQLException {
DatabaseInfo databaseInfo = null;
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
ArrayList list = new ArrayList<>();
try {
//1.获取连接
conn = JdbcUtils.getConnection();
//2.获取PreparedStatement，用于发送sql
String sql = "select t.TABLE_SCHEMA as DATAbase_NAME,CONCAT_Ws('.',t.TABLE_SCHEMA,t" +
".TABLE_NAME) as TABLE_NAME,n" +
"t.TABLE_COMMENT,t.TABLE_ROWS,k.COLUMN_NAME as TABLE_KEY n" +
"from INFORMATION_SCHEMA.TABLES as tn" +
"inner join INFORMATION_SCHEMA.KEY_COLUMN_USAGE as kn" +
"on k.TABLE_NAME=t.TABLE_NAME and CONSTRAINT_NAME = 'PRIMARY' and t.TABLE_SCHEMA " +
"= ?";
ps = conn.prepareStatement(sql);
//3.填充占位符
ps.setString(1, "dw");
//4.执行sql,获取ResultSet
rs = ps.executeQuery();
//5.获取结果集中的数据
while (rs.next()) {
String datbase_name = rs.getString("DATAbase_NAME");
String table_name = rs.getString("TABLE_NAME");
String table_comment = rs.getString("TABLE_COMMENT");
Long table_rows = rs.getLong("TABLE_ROWS");
String table_key = rs.getString("TABLE_KEY");
//6.将结果集中获取的散列数据封装进对象
databaseInfo = new DatabaseInfo(datbase_name, table_name, table_comment, table_rows,
table_key);
list.add(databaseInfo);
}
}catch (Exception e){
e.printStackTrace();
}finally {
//7.关闭连接
JdbcUtils.release(conn,ps,rs);
}
return list;
}
四、测试类
@Test
public void test5() throws SQLException, IOException, ClassNotFoundException {
List list = getList();
Iterator iterator = list.iterator();
while (iterator.hasNext()){
DatabaseInfo databaseInfo = iterator.next();
System.out.println(databaseInfo);
}
}
五、完整代码
package com.bigdata.plus;
import com.bigdata.plus.Entity.DatabaseInfo;
import org.junit.Test;
import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Date;
import java.util.Iterator;
import java.util.List;
public class PrepareStatementTest {
@Test
public void test5() throws SQLException, IOException, ClassNotFoundException {
List list = getList();
Iterator iterator = list.iterator();
while (iterator.hasNext()){
DatabaseInfo databaseInfo = iterator.next();
System.out.println(databaseInfo);
}
}
public List getList() throws SQLException {
DatabaseInfo databaseInfo = null;
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
ArrayList list = new ArrayList<>();
try {
//1.获取连接
conn = JdbcUtils.getConnection();
//2.获取PreparedStatement，用于发送sql
String sql = "select t.TABLE_SCHEMA as DATAbase_NAME,CONCAT_Ws('.',t.TABLE_SCHEMA,t" +
".TABLE_NAME) as TABLE_NAME,n" +
"t.TABLE_COMMENT,t.TABLE_ROWS,k.COLUMN_NAME as TABLE_KEY n" +
"from INFORMATION_SCHEMA.TABLES as tn" +
"inner join INFORMATION_SCHEMA.KEY_COLUMN_USAGE as kn" +
"on k.TABLE_NAME=t.TABLE_NAME and CONSTRAINT_NAME = 'PRIMARY' and t.TABLE_SCHEMA " +
"= ?";
ps = conn.prepareStatement(sql);
//3.填充占位符
ps.setString(1, "dw");
//4.执行sql,获取ResultSet
rs = ps.executeQuery();
//5.获取结果集中的数据
while (rs.next()) {
String datbase_name = rs.getString("DATAbase_NAME");
String table_name = rs.getString("TABLE_NAME");
String table_comment = rs.getString("TABLE_COMMENT");
Long table_rows = rs.getLong("TABLE_ROWS");
String table_key = rs.getString("TABLE_KEY");
//6.将结果集中获取的散列数据封装进对象
databaseInfo = new DatabaseInfo(datbase_name, table_name, table_comment, table_rows,
table_key);
list.add(databaseInfo);
}
}catch (Exception e){
e.printStackTrace();
}finally {
//7.关闭连接
JdbcUtils.release(conn,ps,rs);
}
return list;
}
}
六、运行测试类输出如下所示
DatabaseInfo(databaseName=dw, tableName=dw.bak_product, tableComment=, tableRows=0, tableKey=bak_id)
DatabaseInfo(databaseName=dw, tableName=dw.courses, tableComment=, tableRows=16, tableKey=id)
DatabaseInfo(databaseName=dw, tableName=dw.phone, tableComment=, tableRows=0, tableKey=id)
DatabaseInfo(databaseName=dw, tableName=dw.product, tableComment=, tableRows=0, tableKey=id)
DatabaseInfo(databaseName=dw, tableName=dw.student, tableComment=, tableRows=0, tableKey=sid)
DatabaseInfo(databaseName=dw, tableName=dw.stuinfo, tableComment=学生信息表, tableRows=3, tableKey=id)
DatabaseInfo(databaseName=dw, tableName=dw.bak_product, tableComment=, tableRows=0, tableKey=bak_id)
DatabaseInfo(databaseName=dw, tableName=dw.courses, tableComment=, tableRows=16, tableKey=id)
DatabaseInfo(databaseName=dw, tableName=dw.databaseInfo, tableComment=源数据库表信息, tableRows=0, tableKey=id)
DatabaseInfo(databaseName=dw, tableName=dw.phone, tableComment=, tableRows=0, tableKey=id)
DatabaseInfo(databaseName=dw, tableName=dw.product, tableComment=, tableRows=0, tableKey=id)
DatabaseInfo(databaseName=dw, tableName=dw.s_product, tableComment=, tableRows=0, tableKey=p_id)
DatabaseInfo(databaseName=dw, tableName=dw.student, tableComment=, tableRows=0, tableKey=sid)
DatabaseInfo(databaseName=dw, tableName=dw.stuinfo, tableComment=学生信息表, tableRows=3, tableKey=id)
