Implementing Basic CRUD Operations in Java Web
Implementation of basic CRUD operations in Java Web
Overview
After completing Java Web studies, its time to create a simple example of CRUD operations.
- What is pandas?
Example: Pandas is a tool based on NumPy, created to solve data analysis tasks.
- Usage Steps
1. Mapper Layer
package org.example.mapper;
import org.apache.ibatis.annotations.*;
import org.example.pojo.Brand;
import java.util.List;
public interface BrandMapper {
/**
* Retrieve all
* @return
*/
@Select("select * from tb_brand")
List<Brand> selectAll();
/**
* Add data
* @param brand
*/
@Insert("insert into tb_brand values (null,#{brandName},#{companyName},#{ordered},#{description},#{status})")
void add(Brand brand);
/**
* Batch delete
* @param ids
*/
void deleteByIds(@Param("ids") int[] ids);
/**
* Single delete
*/
@Delete("delete from tb_brand where id = #{id}")
void deleteById(int id);
/**
* Update
* @param brand
*/
@Update("update tb_brand set brand_name = #{brandName},company_name = #{companyName},ordered = #{ordered},description = #{description},status = #{status} where id = #{id}")
void update(Brand brand);
/**
* Paginate query
* @param begin
* @param size
* @return
*/
@Select("select * from tb_brand limit #{begin},#{size}")
List<Brand> selectByPage(@Param("begin") int begin,@Param("size") int size);
/**
* Count total records
* @return
*/
@Select("select count(*) from tb_brand")
int selectTotalCount();
/**
* Paginate with condition query
* @param begin
* @param size
* @param brand
* @return
*/
List<Brand> selectByPageAndCondition(@Param("begin") int begin,@Param("size") int size,@Param("brand") Brand brand);
/**
* Count total records with condition
* @return
*/
int selectTotalCountByCondition(Brand brand);
2. Pojo Layer
package org.example.pojo;
import java.sql.Date;
public class Brand {
// ID primary key
private Integer id;
// Brand name
private String brandName;
// Company name
private String companyName;
// Sort field
private Integer ordered;
// Description information
private String description;
// Status: 0: disabled, 1: enabled
private Integer status;
public Date getDate() {
return date;
}
public void setDate(Date date) {
this.date = date;
}
public Date getBackdate() {
return backdate;
}
public void setBackdate(Date backdate) {
this.backdate = backdate;
}
private Date date;
private Date backdate;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getBrandName() {
return brandName;
}
public void setBrandName(String brandName) {
this.brandName = brandName;
}
public String getCompanyName() {
return companyName;
}
public void setCompanyName(String companyName) {
this.companyName = companyName;
}
public Integer getOrdered() {
return ordered;
}
public void setOrdered(Integer ordered) {
this.ordered = ordered;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public Integer getStatus() {
return status;
}
// Logical view
public String getStatusStr(){
if (status == null){
return "unknown";
}
return status == 0 ? "out of stock":"normal";
}
public void setStatus(Integer status) {
this.status = status;
}
@Override
public String toString() {
return "Brand{" +
"id=" + id +
", brandName='" + brandName + "'" +
", companyName='" + companyName + "'" +
", ordered=" + ordered +
", description='" + description + "'" +
", status=" + status +
", date=" + date +
", backdate=" + backdate +
'}';
}
}
PageBean Pojo for Pagination
package org.example.pojo;
import java.util.List;
// JavaBean for pagination query
public class PageBean<T> {
// Total number of records
private int totalCount;
// Current page data
private List<T> rows;
public int getTotalCount() {
return totalCount;
}
public void setTotalCount(int totalCount) {
this.totalCount = totalCount;
}
public List<T> getRows() {
return rows;
}
public void setRows(List<T> rows) {
this.rows = rows;
}
}
Service Layer
package org.example.service;
import org.example.mapper.BrandMapper;
import org.example.pojo.Brand;
import org.example.pojo.PageBean;
import org.example.util.SqlSessionFactoryUtils;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.example.pojo.PageBean;
import java.util.List;
public class BrandService {
// 1. Create the corresponding SqlSessionFactory factory object
SqlSessionFactory factory = SqlSessionFactoryUtils.getSqlSessionFactory();
/**
* Query data
* @return
*/
public List<Brand> selectAll() {
// 2. Get SqlSession object
SqlSession sqlSession = factory.openSession();
// 3. Get BrandMapper
BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);
// 4. Call method
List<Brand> brands = mapper.selectAll();
// 5. Release resources
sqlSession.close();
return brands;
}
/**
* Add data
* @param brand
*/
public void add(Brand brand){
// 2. Get SqlSession object
SqlSession sqlSession = factory.openSession();
// 3. Get BrandMapper
BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);
// 4. Call method
mapper.add(brand);
// Commit transaction
sqlSession.commit();
// 5. Release resources
sqlSession.close();
}
/**
* Batch delete
* @param ids
*/
public void deleteByIds(int[] ids){
// 2. Get SqlSession object
SqlSession sqlSession = factory.openSession();
// 3. Get BrandMapper
BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);
// 4. Call method
mapper.deleteByIds(ids);
// Commit transaction
sqlSession.commit();
// 5. Release resources
sqlSession.close();
}
/**
* Single delete
* @param id
*/
public void deleteById(int id){
// 2. Get SqlSession object
SqlSession sqlSession = factory.openSession();
// 3. Get BrandMapper
BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);
// 4. Call method
mapper.deleteById(id);
// Commit transaction
sqlSession.commit();
// 5. Release resources
sqlSession.close();
}
/**
* Update
* @param brand
*/
public void update(Brand brand){
// 2. Get SqlSession
SqlSession sqlSession = factory.openSession();
// 3. Get BrandMapper
BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);
// 4. Call method
mapper.update(brand);
// Commit transaction
sqlSession.commit();
// Release resources
sqlSession.close();
}
/**
*
* @param currentPage Current page number
* @param pageSize Number of items per page
* @return
*/
public PageBean<Brand> selectByPage(int currentPage, int pageSize){
// 2. Get SqlSession object
SqlSession sqlSession = factory.openSession();
// 3. Get BrandMapper
BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);
// 4. Calculate start index
int begin = (currentPage-1) * pageSize;
// Calculate number of items to retrieve
int size = pageSize;
// 5. Retrieve current page data
List<Brand> rows = mapper.selectByPage(begin, size);
// 6. Retrieve total record count
int totalCount = mapper.selectTotalCount();
// 7. Encapsulate PageBean object
PageBean<Brand> pageBean = new PageBean<>();
pageBean.setRows(rows);
pageBean.setTotalCount(totalCount);
// 8. Release resources
sqlSession.close();
return pageBean;
}
/**
* Paginate with condition query
* @param currentPage
* @param pageSize
* @param brand
* @return
*/
public PageBean<Brand> selectByPageAndCondition(int currentPage,int pageSize,Brand brand){
// 2. Get SqlSession object
SqlSession sqlSession = factory.openSession();
// 3. Get BrandMapper
BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);
// 4. Calculate start index
int begin = (currentPage-1) * pageSize;
// Calculate number of items to retrieve
int size = pageSize;
// Process brand condition for fuzzy query
String brandName = brand.getBrandName();
if(brandName != null && brandName.length()>0){
brand.setBrandName("%"+brandName+"%");
}
String companyName = brand.getCompanyName();
if(companyName != null && companyName.length()>0){
brand.setCompanyName("%"+companyName+"%");
}
// 5. Retrieve current page data
List<Brand> rows = mapper.selectByPageAndCondition(begin, size,brand);
// 6. Retrieve total record count
int totalCount = mapper.selectTotalCountByCondition(brand);
// 7. Encapsulate PageBean object
PageBean<Brand> pageBean = new PageBean<>();
pageBean.setRows(rows);
pageBean.setTotalCount(totalCount);
// 8. Release resources
sqlSession.close();
return pageBean;
}
}
Servlet Layer
Link: https://pan.baidu.com/s/1nFJ-3mC5znfBFgTm-oAw6g Code: 1fka
Summary
When implementing basic CRUD operations, many issues may arise, such as filters preventing recognition of Vue, or SQL problems when adding data. Stay calm.
