看程序学mybatis 注解5 - 注解方式的动态SQL语句

步骤 3 : 基于手写SQL语句的注解CRUD
把手写SQL语句的注解CRUD，修改为动态SQL语句方式。
步骤 4 : CategoryDynaSqlProvider
新增CategoryDynaSqlProvider，提供CRUD对应的SQL语句。
这里的SQL语句使用SQL类的方式构建

package com.how2java;
 
import org.apache.ibatis.jdbc.SQL;
 
public class CategoryDynaSqlProvider {
    public String list() {
         return new SQL()
                 .SELECT("*")
                 .FROM("category_")
                 .toString();
         
    }
    public String get() {
        return new SQL()
                .SELECT("*")
                .FROM("category_")
                .WHERE("id=#{id}")
                .toString();
    }
     
    public String add(){
        return new SQL()
                .INSERT_INTO("category_")
                .VALUES("name", "#{name}")
                .toString();
    }
    public String update(){
        return new SQL()
                .UPDATE("category_")
                .SET("name=#{name}")
                .WHERE("id=#{id}")
                .toString();
    }
    public String delete(){
        return new SQL()
                .DELETE_FROM("category_")
                .WHERE("id=#{id}")
                .toString();
    }
     
}

步骤 5 : 修改CategoryMapper
把本来是手写SQL的CategoryMapper接口，修改为注解引用CategoryDynaSqlProvider类的方式
比如增加，本来是手写SQL语句的

@Insert(" insert into category_ ( name ) values (#{name}) ")
public int add(Category category);

修改为了注解@InsertProvider配合CategoryDynaSqlProvider的add方法

@InsertProvider(type=CategoryDynaSqlProvider.class,method=“add”)
public int add(Category category);

package com.how2java.mapper;
  
import java.util.List;
 
import org.apache.ibatis.annotations.DeleteProvider;
import org.apache.ibatis.annotations.InsertProvider;
import org.apache.ibatis.annotations.SelectProvider;
import org.apache.ibatis.annotations.UpdateProvider;
 
import com.how2java.CategoryDynaSqlProvider;
import com.how2java.pojo.Category;
  
public interface CategoryMapper {
  
    @InsertProvider(type=CategoryDynaSqlProvider.class,method="add") 
    public int add(Category category); 
        
    @DeleteProvider(type=CategoryDynaSqlProvider.class,method="delete")
    public void delete(int id); 
        
    @SelectProvider(type=CategoryDynaSqlProvider.class,method="get") 
    public Category get(int id); 
      
    @UpdateProvider(type=CategoryDynaSqlProvider.class,method="update") 
    public int update(Category category);  
        
    @SelectProvider(type=CategoryDynaSqlProvider.class,method="list")     
    public List<Category> list(); 
}

步骤 6 : 查询测试
用同样的测试类，进行CRUD测试。注意，id值需要根据实际情况调整

package com.how2java;
   
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
 
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
 
import com.how2java.mapper.CategoryMapper;
import com.how2java.pojo.Category;
   
public class TestMybatis {
   
    public static void main(String[] args) throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();
        CategoryMapper mapper = session.getMapper(CategoryMapper.class);
  
//        add(mapper);
//        delete(mapper);
//        get(mapper);
//        update(mapper);
        listAll(mapper);
              
        session.commit();
        session.close();
   
    }
  
    private static void update(CategoryMapper mapper) {
        Category c= mapper.get(14);
        c.setName("修改了的Category名稱");
        mapper.update(c);
        listAll(mapper);
    }
  
    private static void get(CategoryMapper mapper) {
        Category c= mapper.get(14);
        System.out.println(c.getName());
    }
  
    private static void delete(CategoryMapper mapper) {
        mapper.delete(13);
        listAll(mapper);
    }
  
    private static void add(CategoryMapper mapper) {
        Category c = new Category();
        c.setName("新增加的Category");
        mapper.add(c);
        listAll(mapper);
    }
   
    private static void listAll(CategoryMapper mapper) {
        List<Category> cs = mapper.list();
        for (Category c : cs) {
            System.out.println(c.getName());
        }
    }
}

步骤 7 : 关于SQL类

SQL类是用于进行动态SQL生成的，如下代码是一个相对复杂的SQL类的使用举例，以后需要用到的时候，再来参考。

private String selectPersonSql() {
  return new SQL() {{
    SELECT("P.ID, P.USERNAME, P.PASSWORD, P.FULL_NAME");
    SELECT("P.LAST_NAME, P.CREATED_ON, P.UPDATED_ON");
    FROM("PERSON P");
    FROM("ACCOUNT A");
    INNER_JOIN("DEPARTMENT D on D.ID = P.DEPARTMENT_ID");
    INNER_JOIN("COMPANY C on D.COMPANY_ID = C.ID");
    WHERE("P.ID = A.ID");
    WHERE("P.FIRST_NAME like ?");
    OR();
    WHERE("P.LAST_NAME like ?");
    GROUP_BY("P.ID");
    HAVING("P.LAST_NAME like ?");
    OR();
    HAVING("P.FIRST_NAME like ?");
    ORDER_BY("P.ID");
    ORDER_BY("P.FULL_NAME");
  }}.toString();
}