Java开发学习(6)
人事管理系统从无到有5
把昨天的测试写入DAO层 增删改查
条件查询通过主键（id）来查询只会返回一个， 非主键来查询会返回多个
//findById//
public User findById(int id) {
User user = null;//声明对象
try {
Connection conn = MySqlDbUtil.getConnect();
String sql ="SELECT * FROM user WHERE id=? ";
PreparedStatement pstmt =conn.prepareStatement(sql);
pstmt.setInt(1,id);
ResultSet rs =pstmt.executeQuery();//结果集 excel表格
if(rs.next()){
user = new User();//实例化
user.setId(rs.getInt("id"));
user.setLoginName(rs.getString("loginName"));//常量改成变量
user.setLoginPwd(rs.getString("loginPwd"));
user.setNickname(rs.getString("nickname"));
user.setIden(rs.getString("iden"));
// System.out.println(" id="+ id + " loginName=" + loginName + " loginPwd=" + loginPwd +" nickname=" + nickname +" iden=" + iden);
}
rs.close();
pstmt.close();
conn.close();
}catch (Exception e){
e.printStackTrace();
}
return user;//返回user
}
//findAll//需要遍历
public List<User> findAll() {//遍历
List<User> users = new ArrayList<>();
try {
Connection conn = MySqlDbUtil.getConnect();
String sql = "SELECT * FROM user";
PreparedStatement pstmt = conn.prepareStatement(sql);
ResultSet rs = pstmt.executeQuery();
while(rs.next()){
User user = new User();
user.setId(rs.getInt("id"));
user.setLoginName(rs.getString("loginName"));
user.setLoginPwd(rs.getString("loginPwd"));
user.setNickname(rs.getString("nickname"));
user.setIden(rs.getString("iden"));
users.add(user);
}
rs.close();
pstmt.close();
conn.close();
} catch (Exception e) {
e.printStackTrace();
}
return users;
}
写测试类测试一下方法。。。
要测试的时候出错了IDEACould not load class with name
无法运行这个类，按照网上方法不行，自己改了文件
通过右键选中Mark Directory as，接着设置为Test Sources Root(绿色)即可
条件查询
@Override
public List<User> find(User user) {
String sql = "SELECT * FROM user WHERE 1=1";
List<Object> params =new ArrayList<>();
if(user!=null){
if(user.getLoginName()!=null&&!"".equals(user.getLoginName())){
sql = sql +"AND loginName LIKE ?";
params.add("%" +user.getLoginName() +"%");
}
if(user.getIden()!=null&&!"".equals(user.getIden())){
sql = sql +"AND iden LIKE ?";
params.add("%" +user.getIden() +"%");
}
}
List<User> users = new ArrayList<>();
try {
Connection conn = MySqlDbUtil.getConnect();
// String sql = "SELECT * FROM user";
PreparedStatement pstmt = conn.prepareStatement(sql);
int i = 0;
for(Object obj:params){
i ++;
pstmt.setObject(i,obj);
}
ResultSet rs = pstmt.executeQuery();
while(rs.next()){
User user1 = new User();
user1.setId(rs.getInt("id"));
user1.setLoginName(rs.getString("loginName"));
user1.setLoginPwd(rs.getString("loginPwd"));
user1.setNickname(rs.getString("nickname"));
user1.setIden(rs.getString("iden"));
users.add(user1);
}
rs.close();
pstmt.close();
conn.close();
} catch (Exception e) {
e.printStackTrace();
}
return users;
}
@Test
public void testFind(){
IUserDao dao =new UserDao();
User u = new User();
u.setLoginName("多");
List<User> users = dao.find(u);
for(User user : users){
System.out.println(user.toString());
}
}
String sql = "SELECT * FROM user WHERE 1=1";
sql = sql +" AND loginName LIKE ? ";
引号前面要有空格。。。
分页查询的util
package cn.edu.mju.wjy29.utils;
import java.util.List;
/**
分页查询
*/
public class Pager {
private int page = 1;
private int pageSize = 10;
private int rows;
private int pages;
private boolean first = true;
private boolean last = false;
private int prev = 1;
private int next = 1;
private List<Object> data;
public Pager() {
}
public Pager(int page, int pageSize) {
this.page = page;
this.pageSize = pageSize;
}
public int getPage() {
if(page > pages){
return pages;
}else {
return page;
}
}
public void setPage(int page) {
if(page < 1){
page = 1;
}
this.page = page;
}
public int getPrev() {
prev = page -1;
if(prev<1){
prev = 1;
}
return prev;
}
public int getNext() {
getPages();
next = page + 1;
if(next > pages){
next = pages;
}
return next;
}
public int getPageSize() {
return pageSize;
}
public void setPageSize(int pageSize) {
if(pageSize<1){
pageSize = 10;
}
this.pageSize = pageSize;
}
public int getRows() {
return rows;
}
public void setRows(int rows) {
this.rows = rows;
getPages();
}
public int getPages() {
pages = (rows / pageSize);
if(pages*pageSize < rows){
pages = pages + 1;
}
return pages;
}
public boolean isFirst() {
if(page == 1){
return true;
}else{
return false;
}
}
public boolean isLast() {
if(page == pages){
return true;
}else {
return false;
}
}
public List<Object> getData() {
return data;
}
public void setData(List<Object> data) {
this.data = data;
}
}
@Override
public Pager paginate(int page, int pagesize, User user) {
Pager pager =new Pager();
pager.setPageSize(pagesize);
pager.setPage(page);
String sql = "SELECT COUNT(*) AS A FROM user";//取总的记录数
StringBuilder _where = new StringBuilder(" WHERE 1=1");//按条件来取(动态字符串)
List<Object> params =new ArrayList<>();
if(user!=null){
if(user.getLoginName()!=null&&!"".equals(user.getLoginName())){
_where.append(" AND loginName LIKE ? ") ;
params.add("%" +user.getLoginName() +"%");
}
if(user.getIden()!=null&&!"".equals(user.getIden())){
_where.append(" AND iden LIKE ? ");
params.add("%" +user.getIden() +"%");
}
}
Connection conn = null;
try {
conn = MySqlDbUtil.getConnect();
PreparedStatement pst = conn.prepareStatement(sql + _where.toString());
for(int i=0;i < params.size();i++ ){
pst.setObject(i+1,params.get(i));
}
ResultSet rs =pst.executeQuery();
int count = rs.getInt("A");
rs.close();
pst.close();
pager.setRows(count);
page =pager.getPage();
sql ="SELECT *FROM user";
pst = conn.prepareStatement(sql + _where.toString() +"LIMIT ?,?");
int index =0;
for(int i=0;i < params.size();i++ ){
index ++;
pst.setObject(i+1,params.get(i));
}
pst.setInt(index +1,(pager.getPage()-1)*pager.getPageSize());
pst.setInt(index++,pager.getPageSize());
rs = pst.executeQuery();//读数据
List<Object> users = new ArrayList<>();
while(rs.next()){
User user1 = new User();
user1.setId(rs.getInt("id"));
user1.setLoginName(rs.getString("loginName"));
user1.setLoginPwd(rs.getString("loginPwd"));
user1.setNickname(rs.getString("nickname"));
user1.setIden(rs.getString("iden"));
users.add(user1);
}
pager.setData(users);
rs.close();
pst.close();
} catch (Exception e) {
e.printStackTrace();
}
return pager;
}