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一.QueryRunner类实现增删改
连接池代码:JdbcUtil.java
package com.wb.util;
/** * c3p0,dbcp,druid */
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;
import javax.sql.DataSource;
import com.alibaba.druid.pool.DruidDataSource;
import com.alibaba.druid.pool.DruidDataSourceFactory;
/** * 绝对不能使用单例 * * @author Administrator 硬编码 */
public class JdbcUtil {
private static Connection con = null;
private static DataSource ds = null;
private static Properties pt = null;
static {
// 1.获得当前类的加载器
ClassLoader cl = JdbcUtil.class.getClassLoader();
// 通过该加载器得到一个输入流
InputStream in = cl.getResourceAsStream("jdbc.properties");
// 通过输入创一个properties对象
pt = new Properties();
try {
pt.load(in);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static Connection getCon() {
if (ds == null) {
try {
ds = (DruidDataSource) DruidDataSourceFactory.createDataSource(pt);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
try {
return ds.getConnection();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
public static void closeCon(Connection con) {
try {
con.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
具体使用模板:
public static void main(String[] args) throws Exception{
//使用自己的工具类,获取数据库的连接对象
Connection conn = MyJDBCUtils.getConnection();
//创建QueryRunner类对象
QueryRunner qr = new QueryRunner();
String sql = "UPDATE gjp_ledger set money=? , ldesc=? where lid=?";
Object[] params = {
998,"买钻石",3};
int result = qr.update(conn, sql, params);
System.out.println(result);
DbUtils.close(conn);
}
二.QueryRunner类获取查询结果集ResultSetHandler
1.常用Handler
- ArrayHandler 将结果集第一行转成对象数组
public static void main(String[] args) throws Exception{
Connection conn = MyJDBCUtils.getConnection();
String sql = "SELECT * FROM gjp_ledger where lid=?";
//结果集处理方式,ArrayHandler 第一行转成对象数组
QueryRunner qr = new QueryRunner();
Object[] objects = qr.query(conn, sql, new ArrayHandler(),3);
for(Object obj : objects){
System.out.println(obj);
}
}
- ArrayListHandler 将结果集中的每一行数据都转成一个对象数组,再将转成的多个对象数组存放到List
public static void main(String[] args) throws Exception{
Connection conn = MyJDBCUtils.getConnection();
String sql = "SELECT * FROM gjp_ledger";
QueryRunner qr = new QueryRunner();
//执行query方法,传递连接对象,SQL语句,结果集处理方式
ArrayListHandler
List<Object[]> list = qr.query(conn, sql, new ArrayListHandler());
for(Object[] objects : list){
for(Object obj : objects){
System.out.print(obj+" ");
}
System.out.println();
}
}
- BeanHandler 将结果集第一行数据封装到一个对应的业务类实例中
(1): 定义业务数据类Ledger(实体类,javaBean)
public class Ledger {
//要生成空参、有参构造、set和get方法、toString方法
private int lid;
private String parent;
private double money;
private int sid;
private String account;
private String createtime;
private String ldesc;
}
(2)测试案例代码
public static void main(String[] args) throws Exception{
Connection conn = MyJDBCUtils.getConnection();
String sql = "SELECT * FROM gjp_ledger";
QueryRunner qr = new QueryRunner();
//BeanHandler泛型,构造方法(和反射有关系的对象)
Ledger legder = qr.query(conn, sql, new BeanHandler<Ledger>(Ledger.class));
System.out.println(legder);
}
- BeanListHandler 将结果集中的每一行数据都封装到一个对应的业务类实例中,再将多个业务类实例对象存放到List里。
public static void main(String[] args) throws Exception {
Connection conn = MyJDBCUtils.getConnection();
String sql = "SELECT * FROM gjp_ledger";
//结果集处理方式,BeanListHandler 每一行数据封装到业务数据类中
QueryRunner qr = new QueryRunner();
List list = qr.query(conn, sql, new BeanListHandler(Ledger.class));
for(Ledger ledger : list){
System.out.println(ledger);
}
}
- MapHandler 将结果集中的第一行数据封装到一个Map中,key是列名,value是对应的值。
public static void main(String[] args) throws Exception {
Connection conn = MyJDBCUtils.getConnection();
String sql = "SELECT * FROM gjp_ledger";
//结果集处理方式,MapHandler 封装到一个Map集合中,存储键值对集合
QueryRunner qr = new QueryRunner();
Map<String,Object> map = qr.query(conn, sql,new MapHandler());
for(String key : map.keySet()){
System.out.println(key+" "+map.get(key));
}
}
- MapListHandler 将结果集中的每一行数据都封装到一个Map里,然后再将多个Map存放到List
public static void main(String[] args) throws Exception{
Connection conn = MyJDBCUtils.getConnection();
String sql = "SELECT * FROM gjp_ledger";
//结果集处理方式,MapListHandler 数据中的每一行封装成Map集合,多个Map集合存储到List集合
QueryRunner qr = new QueryRunner();
List<Map<String,Object>> list = qr.query(conn, sql,new MapListHandler());
for(Map<String,Object> map : list){
for(String key : map.keySet()){
System.out.print(key+" "+map.get(key));
}
System.out.println();
多表联合查询
QueryRunner qr = new QueryRunner();
@Override
public List<Emp> getEmpList(Integer pageSize, Integer pageIndex, String empName) {
List<Emp> empList = new ArrayList<Emp>();
/* //使用new BeanListHandler<>(Emp.class);会导致集合里面字段为空 Connection con = JdbcUtil.getCon(); String sql = "select emp_id empId,emp_name empName,emp_phone empPhone,emp_age empAge,emp_sex empSex,e.depa_id depaId, d.depa_name depaName FROM emp e INNER JOIN depa d ON e.depa_id=d.depa_id WHERE e.emp_name like ? limit ?,?"; try { empList = qr.query(con, sql, new BeanListHandler<>(Emp.class), empName == null || "".equals(empName) ? "%%" : "%" + empName + "%", (pageIndex - 1) * pageSize, pageSize); } catch (SQLException e) { e.printStackTrace(); } finally { JdbcUtil.closeCon(con); } for (int i = 0; i < empList.size(); i++) { System.out.println(empList.get(i)); }*/
//使用 new MapListHandler() 需要手动遍历
Connection con = JdbcUtil.getCon();
String sql = "select emp_id,emp_name,emp_phone,emp_age,emp_sex,e.depa_id, depa_name FROM emp e INNER JOIN depa d ON e.depa_id=d.depa_id WHERE e.emp_name like ? limit ?,?";
try {
List<Map<String,Object>> list = qr.query(con, sql, new MapListHandler(),
empName == null || "".equals(empName) ? "%%" : "%" + empName + "%",
(pageIndex - 1) * pageSize, pageSize);
for(Map<String,Object> map:list){
Emp emp = new Emp();
for(String key: map.keySet()){
switch (key) {
case "emp_id":
emp.setEmpId((Integer) map.get(key));
break;
case "emp_sex":
emp.setEmpSex((String) map.get(key));
break;
case "emp_age":
emp.setEmpAge((Integer) map.get(key));
break;
case "emp_phone":
emp.setEmpPhone((String) map.get(key));
break;
case "emp_name":
emp.setEmpName((String) map.get(key));
break;
case "depa_id":
emp.setDepaId((Integer) map.get(key));
break;
case "depa_name":
emp.setDepaName((String) map.get(key));
break;
default:
System.out.println("发生异常");
break;
}
//System.out.println(key+"---"+map.get(key));
}
empList.add(emp);
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
JdbcUtil.closeCon(con);
}
for (int i = 0; i < empList.size(); i++) {
System.out.println(empList.get(i));
}
return empList;
}
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