前言：通过前几章对jdbc有个大概的了解，但是我们在做项目的时候，我们是不是想有没有更好更强大的工具类呢，这个类既包括了连接池，优化查询的方法，返回处理的结果。ok，今天就来介绍一个jdbc常用的一个强大的工具类dbutils类，他是apache组织的一个工具类,jdbc的框架,更方便我们使用！
---------使用步骤------
1.导入jar包(commons-dbutils-1.4.jar)。注意：是在c3p0类的基础上的。
2.创建一个queryrunner类，queryrunner作用:操作sql语句，构造方法:new QueryRunner(Datasource ds);
3.编写sql
4.执行sql，query(..):执行r操作，update(...):执行cud操作
---------代码Demo------
1.封装一个简单的DataSourceUtils类：
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.sql.DataSource;
import com.mchange.v2.c3p0.ComboPooledDataSource;
public class DataSourceUtils {
private static ComboPooledDataSource ds = new ComboPooledDataSource();
/**
* 获取数据源
*
* @return连接池
*/
public static DataSource getDataSource() {
return ds;
}
/**
* 获取连接
*
* @return
* @throws SQLException
*/
public static Connection getConnection() throws SQLException {
return ds.getConnection();
}
public static void closeResource(Connection conn, Statement st, ResultSet rs) {
closeResultSet(rs);
closeStatement(st);
closeConn(conn);
}
private static void closeConn(Connection conn) {
if (conn != null) {
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
conn = null;
}
}
private static void closeStatement(Statement st) {
if (st != null) {
try {
st.close();
} catch (SQLException e) {
e.printStackTrace();
}
st = null;
}
}
private static void closeResultSet(ResultSet rs) {
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
rs = null;
}
}
}
3.CURDDemo：
import java.sql.SQLException;
import javax.sql.DataSource;
import org.apache.commons.dbutils.QueryRunner;
import org.junit.Test;
import com.fly.utils.DataSourceUtils;
public class CURDDemo {
@Test
public void insert() throws SQLException {
// 1创建queryrunner类
QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
// 2编写sql
String sql = "insert into category values(?,?);";
// 执行sql
qr.update(sql, "c2025", "厨房电气25");
}
public void update() throws SQLException {
QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "update category set cname = ? where cid = ?";
qr.update(sql, "达电器", "c001");
}
}
----------QueryRunner类------------
1.作用：操作sql语句
2.构造器：new QueryRunner(Datasource ds);
3.注意：底层帮我们创建连接,创建语句执行者 ,释放资源.
4.常用方法：query(..)、update(..):
---------DbUtils------------
1.释放资源,控制事务 类
2.closeQuietly(conn):内部处理了异常
3.commitAndClose(Connection conn):提交事务并释放连接
---------ResultSetHandler:封装结果集 接口--------
0.javabean：
public class Category {
private String cid;
private String cname;
public String getCid() {
return cid;
}
public void setCid(String cid) {
this.cid = cid;
}
public String getCname() {
return cname;
}
public void setCname(String cname) {
this.cname = cname;
}
@Override
public String toString() {
return "Category [cid=" + cid + ", cname=" + cname + "]";
}
}1.(了解)ArrayHandler, 将查询结果的第一条记录封装成数组,返回
@Test
public void arrayHandler() throws SQLException {
QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "select * from category";
// String sql = "select * from user";
Object[] query = qr.query(sql, new ArrayHandler());
System.out.println(Arrays.toString(query));
}2.(了解)ArrayListHandler, 将查询结果的每一条记录封装成数组,将每一个数组放入list中返回
@Test
public void arrayListHandler() throws SQLException {
QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "select * from category";
List<Object[]> list = qr.query(sql, new ArrayListHandler());
for (Object[] obj : list) {
System.out.println(Arrays.toString(obj));
}
}3.★★BeanHandler, 将查询结果的第一条记录封装成指定的bean对象,返回
@Test
public void beanHandler() throws SQLException {
QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "select * from category";
Category bean = qr.query(sql, new BeanHandler<>(Category.class));
System.out.println(bean);
}4. ★★BeanListHandler, 将查询结果的每一条记录封装成指定的bean对象,将每一个bean对象放入list中 返回.
@Test
public void beanListHandler() throws SQLException {
QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "select * from category";
List<Category> list = qr.query(sql, new BeanListHandler<>(
Category.class));
for (Category bean : list) {
System.out.println(bean);
}
}5. (了解)ColumnListHandler, 将查询结果的指定一列放入list中返回
6. (了解)MapHandler, 将查询结果的第一条记录封装成map,字段名作为key,值为value 返回
@Test
public void mapHandler() throws SQLException {
QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "select * from category";
Map<String, Object> map = qr.query(sql, new MapHandler());
System.out.println(map);
}7. ★MapListHandler, 将查询结果的每一条记录封装map集合,将每一个map集合放入list中返回
@Test
public void mapListHandler() throws SQLException {
QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "select * from category";
List<Map<String, Object>> list = qr.query(sql, new MapListHandler());
for (Map<String, Object> map : list) {
System.out.println(map);
}
}8.★ScalarHandler,针对于聚合函数 例如:count(*) 返回的是一个Long值
@Test
public void scalarHandler() throws SQLException {
QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
String sql = "select count(*) from category";
Object obj = qr.query(sql, new ScalarHandler());
System.out.println(obj.getClass().getName());
}