資料庫操作工具-QueryRunner
阿新 • • 發佈:2019-02-05
在相繼學習了JDBC和資料庫操作之後,我們明顯感到編寫JDBC程式碼並非一件輕鬆的事兒。為了幫助我們更高效的學習工作,從JDBC的繁重程式碼中解脫出來,老佟給我們詳盡介紹了一個簡化JDBC操作的元件——DBUtils。我們今天主要學習了它所提供的兩個類和一個介面。
元件下載地址:http://commons.apache.org/proper/commons-dbutils/
- DbUtils類(org.apache.commons.dbutils.DbUtils)主要負責裝載驅動、關閉連線的常規工作
方法:
- close: 檢查所提供的引數是不是NULL,如果不是的話,它們就關閉連線、宣告和結果集。
- CloseQuietly:避免連線、宣告或結果集為NULL的情況被關閉
- CommitAndCloseQuietly(Connection conn):用來提交連線,然後關閉連線,並且在關閉連線時不向上丟擲在關閉時發生的一些SQL異常。
- LoadDriver(String driveClassName): 裝載並註冊JDBC驅動程式,如果成功就返回TRUE。
- QreryRunner類(org.apache.commons.dbutils.QueryRunner) 顯著的簡化了SQL查詢,並與ResultSetHandler協同工作將使編碼量大為減少
- query(Connection conn, String sql, Object[] params, ResultSetHandler rsh):執行選擇查詢,在查詢中,物件陣列的值被用來作為查詢的置換引數。
- query(String sql, Object[] params, ResultSetHandler rsh):方法本身不提供資料庫連線,執行選擇查詢,在查詢中,物件陣列的值被用來作為查詢的置換引數。
- query(Connection conn, String sql, ResultSetHandler rsh):執行無需引數的選擇查詢。
- update(Connection conn, String sql, Object[] params):被用來執行插入、更新或刪除(DML)操作。
ResultSetHandler介面(org.apache.commons.dbutils.ResultSethandler)執行處理一個結果集物件,將資料轉變並處理為任何一種形式,供其他應用使用。
Object handle (java.sql.ResultSet .rs) :結果集(ResultSet)作為引數傳入方法內,處理這個結果集,返回一個物件。
ArrayHandler ArrayListHandler BeanHandler BeanListHandler MapHandler MapListHandler ScalarHandler
學習了此元件的兩個類和一個介面以後,寫了下列程式碼供參考:
import java.sql.Connection;
import java.sql.SQLException;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanListHandler;
public class TestQueryRunner {
public static void main(String[] args) throws SQLException {
// TODO Auto-generated method stub
//queryOracle();
update();
}
private static void update() throws SQLException{
QueryRunner runner = new QueryRunner();
Connection conn = DBManager.getConnection();
//刪除非 manager 中工資 低於 5000 的員工
String sql = "UPDATE examstudent SET student_name = ? WHERE flow_id = ?";
Object [] params = new Object[]{"Jerry", 5000};
runner.update(conn, sql, params);
}
private static void insert() throws SQLException{
QueryRunner runner = new QueryRunner();
Connection conn = DBManager.getConnection();
//刪除非 manager 中工資 低於 5000 的員工
String sql = "INSERT INTO examstudent(flow_id, type, id_card, exam_card, student_name, location, grade) VALUES(?, ?, ?, ?, ?, ?, ?)";
Object [] params = new Object[]{5000, 6, "身份證", "准考證", "Tom", "北京", 99};
runner.update(conn, sql, params);
}
private static void delete() throws SQLException{
QueryRunner runner = new QueryRunner();
Connection conn = DBManager.getConnection();
//刪除非 manager 中工資 低於 5000 的員工
String sql = "delete from employees " +
"where employee_id not in " +
" (select distinct d.manager_id from departments d where d.manager_id is not null) " +
"and salary < ?";
System.out.println(sql);
Object [] params = new Object[]{5000};
runner.update(conn, sql, params);
}
private static void queryOracle() throws SQLException{
QueryRunner runner = new QueryRunner();
Connection conn = DBManager.getConnection();
//oracle 中的別名可以別解析
String sql = "SELECT flow_id flowid, type, id_card idcard, exam_card examcard, student_name studentname, location, grade FROM examstudent";
Object obj = runner.query(conn, sql, new BeanListHandler(ExamStudent.class));
System.out.println(obj);
}
private static void query() throws SQLException {
//1. 建立一個 QueryRunner 的例項
QueryRunner runner = new QueryRunner();
Connection conn = DBManager.getConnection();
String sql = "SELECT id, name, address, phone FROM customers WHERE name LIKE ?";
Class type = Customer.class;
Object [] params = new Object[]{"%%"};
//2. 查詢操作
//conn: 查詢需要的資料庫連線, sql: 查詢使用的 sql 語句, rsh: 如何轉換查詢得到的結果集, params: 填補 sql 語句引數的陣列
Object obj = runner.query(conn, sql, new BeanListHandler(type), params);
//System.out.println("^^" + obj);
sql = "SELECT flow_id flowid, type, id_card idcard, exam_card examcard, student_name studentname, location, grade FROM examstudent";
type = ExamStudent.class;
obj = runner.query(conn, sql, new BeanListHandler(ExamStudent.class));
System.out.println(obj);
}
}
public class JdbcUtil {
private static ComboPooledDataSource dataSource =new ComboPooledDataSource();
public static ComboPooledDataSource getDataSource()
{
return dataSource;
}
}
src目錄下c3p0-config.xml
重要程式碼摘錄
從資料庫中取count(*)資料:
int topicNum=0;
QueryRunner runner= new QueryRunner(JdbcUtil.getDataSource());
String sql ="select count(*) from topic where type_id= ? order by time desc";
Object[] params={typeId};
topicNum=(int)(long) runner.query(sql,new ScalarHandler(),params);
return topicNum;
取一條資料 其中表的欄位名字和類的名字要對應相同:
Topic newlyTopic=null;
QueryRunner runner= new QueryRunner(JdbcUtil.getDataSource());
String sql ="select * from topic where type_id= ? order by time desc";
Object[] params={typeId};
newlyTopic= runner.query(sql,new BeanHandler<Topic>(Topic.class),params);
return newlyTopic;
取集合資料List<>返回 其中表的欄位名字和類的名字要對應相同:
List<Topic> topicList=new ArrayList<Topic>();
QueryRunner runner= new QueryRunner(JdbcUtil.getDataSource());
String sql ="select * from topic where type_id= ? order by time desc";
Object[] params={typeId};
topicList=runner.query(sql, new BeanListHandler<Topic>(Topic.class),params);
return topicList;
插入:
QueryRunner runner= new QueryRunner(JdbcUtil.getDataSource());
String sql ="insert into topic(name,author,content,time,type_id) values(?,?,?,?,?)";
Object[] params={topic.getName(),topic.getAuthor(),topic.getContent(),topic.getTime(),topic.getTypeId()};
try {
//事務開始
runner.update(sql,params);
//事務提交
} catch (SQLException e) {
e.printStackTrace();
//事務回滾
throw e;
}
更新:
QueryRunner runner= new QueryRunner(JdbcUtil.getDataSource());
String sql ="update topic set name=? , content=? , time=? where id= ?";
Object[] params={topic.getName(),topic.getContent(),topic.getTime(),topic.getId()};
try {
//事務開始
runner.update(sql,params);
//事務提交
} catch (SQLException e) {
e.printStackTrace();
//事務回滾
throw e;
}
轉載:原地址