1.UserInfoDao类中getById简化
未简化：
public UserInfo getById(int id) {
String sql = "select id,user_name ,password from user_info1 where id =?";
//创建一个内部类 获取单个
/*class UserInfoRowMapper implements RowMapper<UserInfo>{
public UserInfo mapRow(ResultSet rs, int rowNum) throws SQLException {
UserInfo userInfo = new UserInfo();
userInfo.setId(rs.getInt("id"));
userInfo.setUserName(rs.getString("user_name"));
userInfo.setPassword(rs.getString("password"));
return userInfo;
}
}*/
简化：
public UserInfo getById(int id) {
String sql = "select id,user_name ,password from user_info1 where id =?";
//下面是简化版
RowMapper rowMapper = (ResultSet rs,int rowNum)->{
UserInfo userInfo = new UserInfo();
userInfo.setId(rs.getInt("id"));
userInfo.setUserName(rs.getString("user_name"));
userInfo.setPassword(rs.getString("password"));
return userInfo;
};
return (UserInfo) jdbcTemplate.queryForObject(sql, rowMapper,id);
}
2.这里获取表中一共有多少个id
UserInfoDao类中写selectAll()
public List<UserInfo> selectAll(){
String sql = "select id,user_name ,password from user_info1 ";
return jdbcTemplate.query(sql, (ResultSet rs, int rowNum)->{
UserInfo userInfo = new UserInfo();
userInfo.setId(rs.getInt("id"));
userInfo.setUserName(rs.getString("user_name"));
userInfo.setPassword(rs.getString("password"));
return userInfo;
});
}
test中改为
package com.jd.test;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.jd.userinfo.dao.UserInfoDao;
import com.jd.vo.UserInfo;
public class Test {
public static void main(String[] args) {
ClassPathXmlApplicationContext applicationContext =new ClassPathXmlApplicationContext("application.xml");
//直接操作Dao层
UserInfoDao userDao = applicationContext.getBean(UserInfoDao.class);
//这里有改动 查询单个id
//UserInfo userInfo1 = userDao.getById(2);
//获取总的id数
int size = userDao.selectAll().size();
System.out.println(size);
applicationContext.close();
}
//运行出错是因为还少一个aop包
}
运行结果如下：
3.下面还有一种方法可以查询单个还可以防止sql注入：
//创建一个内部类 ResultSetExtractor这个接口与前面有区别 可以避免sql注入
class UserInfoResultSet implements ResultSetExtractor<UserInfo>{
@Override
public UserInfo extractData(ResultSet rs) throws SQLException, DataAccessException {
UserInfo userInfo = null;
if(rs.next()) {
userInfo = new UserInfo();
userInfo.setId(rs.getInt("id"));
userInfo.setUserName(rs.getString("user_name"));
userInfo.setPassword(rs.getString("password"));
}
return userInfo;
}
}
return jdbcTemplate.query(sql, new UserInfoResultSet(),id);
}
test中改为：
package com.jd.test;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.jd.userinfo.dao.UserInfoDao;
import com.jd.vo.UserInfo;
public class Test {
public static void main(String[] args) {
ClassPathXmlApplicationContext applicationContext =new ClassPathXmlApplicationContext("application.xml");
//直接操作Dao层
UserInfoDao userDao = applicationContext.getBean(UserInfoDao.class);
//这里有改动 查询单个id
//UserInfo userInfo1 = userDao.getById(2);
//获取总的id数
/*int size = userDao.selectAll().size();
System.out.println(size);*/
UserInfo userInfo1 = userDao.getById(2);
System.out.println(userInfo1);
applicationContext.close();
}
//运行出错是因为还少一个aop包
}
运行结果是：
3.采用list集合
UserInfoDao中：
//下面代码还可以简化
/*class UserInfoResultSet implements ResultSetExtractor<List<UserInfo>>{
@Override
public List<UserInfo> extractData(ResultSet rs) throws SQLException, DataAccessException {
List<UserInfo> list = new ArrayList<>();
while(rs.next()) {
UserInfo userInfo= new UserInfo();
userInfo.setId(rs.getInt("id"));
userInfo.setUserName(rs.getString("user_name"));
userInfo.setPassword(rs.getString("password"));
list.add(userInfo);
}
return list;
}
}
return jdbcTemplate.query(sql, new UserInfoResultSet());*/
return jdbcTemplate.query(sql, (ResultSet rs)->{
List<UserInfo> list = new ArrayList<>();
while(rs.next()) {
UserInfo userInfo = new UserInfo();
userInfo.setId(rs.getInt("id"));
userInfo.setUserName(rs.getString("user_name"));
userInfo.setPassword(rs.getString("password"));
list.add(userInfo);
}
return list;
});
}
test类
package com.jd.test;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.jd.userinfo.dao.UserInfoDao;
import com.jd.vo.UserInfo;
public class Test {
public static void main(String[] args) {
ClassPathXmlApplicationContext applicationContext =new ClassPathXmlApplicationContext("application.xml");
//直接操作Dao层
UserInfoDao userDao = applicationContext.getBean(UserInfoDao.class);
//这里有改动 查询单个id
//UserInfo userInfo1 = userDao.getById(2);
//获取总的id数
int size = userDao.selectAll().size();
System.out.println(size);
/*UserInfo userInfo1 = userDao.getById(2);
System.out.println(userInfo1);*/
applicationContext.close();
}
//运行出错是因为还少一个aop包
}
运行结果：