MyBatis-Plus实用篇超完整教程

@mapper
public interface usermapper extends basemapper<user> {}

/**
  * userservice继承iservice模板提供的基础功能 
  */
public interface userservice extends iservice<user> {}

/**
  * serviceimpl实现了iservice，提供了iservice中基础功能的实现 
  * 若serviceimpl无法满足业务需求，则可以使用自定的userservice定义方法，并在实现类中实现
  */
@service
public class userserviceimpl extends serviceimpl<usermapper,user> implements userservice{}

@data
@tablename("t_user")
public class user {
    private long id;
    private string name;
    private integer age;
    private string email;
}

mybatis-plus:
  global-config:
    db-config:
      # 设置实体类所对应的表的统一前缀
      table-prefix: t_

@data
public class user {
    @tableid(value = "tid")
    private long uid;
    private string name;
    private integer age;
    private string email;
}

@data
public class user {
    @tableid(type = idtype.auto)
    private long uid;
    private string name;
    private integer age;
    private string email;
}

//指定数据库字段名称
@tablefield(value = "email")
private string mail

// 执行的sql语句就变成`关键字`，这样sql就不会报错了
@tablefield(value = "`desc`")
private string desc

@tablefield(exist = false)
private boolean checked;

@tablefield(select = false)
private string password;

// 实体注解-实现模糊查询
@tablefield(condition = sqlcondition.like)
private string name;
// 业务代码
user user = new user();
user.setname("张");
userservice.lambdaquery(user).list();
// 打印sql
select id,user_name,age from user where name like concat('%',?,'%')

userservice.lambdaquery().eq(user::getname,"张").list();

// 方式三：
// 实体注解-实现修改字段时候，前后添加“**” 其中 %s 会填充为字段
@tablefield(update = "concat('**',%s,'**')")
private string name;
// 业务代码
user user = new user();
user.setid(1);
user.setname("张三");
userservice.updatebyid(user);
// 打印sql
update user set name=concat('**',name,'**') where id=?

userservice.lambdaquery().eq(user::getname,"张").list();

// 实体字段注解
@tablefield(fill = fieldfill.insert)
private date createtime;
@tablefield(fill = fieldfill.insert_update)
private date updatetime;
// 枚举类
public enum fieldfill {
    /**
     * 默认不处理
     */
    default,
    /**
     * 插入填充字段
     */
    insert,
    /**
     * 更新填充字段
     */
    update,
    /**
     * 插入和更新填充字段
     */
    insert_update
}

@component
public class mymetaobjecthandler implements metaobjecthandler {
	date date = new date();
    @override
    public void insertfill(metaobject metaobject) {
        this.strictinsertfill(metaobject, "createtime", date.class, date);
        this.strictinsertfill(metaobject, "updatetime", date.class, date);
    }
    @override
    public void updatefill(metaobject metaobject) {
        this.strictupdatefill(metaobject, "updatetime", date.class, date);
    }
}

public enum fieldstrategy {
    /**
     * 忽略判断，所有字段都进行更新和插入
     * 无论什么值，直接拼接，没有值，则拼接null
     */
    ignored,
    /**
     * 只更新和插入非null值
     * 相当于添加if判断，不为null才操作
     * <if test="columnproperty != null">column=#{columnproperty}</if>
     */
    not_null,
    /**
     * 只更新和插入非null值且非空字符串
     * 相当于添加if判断，不为null而且不是空字符串才操作
     * <if test="columnproperty != null and columnproperty!=''">column=#{columnproperty}</if>
     */
    not_empty,
    /**
     * 默认not_null
     */
    default,
    /**
     * 永远不进行更新和插入
     */
    never
}

public void testdeletebyid(){
    int result = usermapper.deletebyid(1527472864163348482l);
    system.out.println(result > 0 ? "删除成功！" : "删除失败！");
    system.out.println("受影响的行数为：" + result);
}

public void testselectlist(){
    list<user> users = usermapper.selectlist(null);
}

 /** 组装修改条件  将(年龄大于20并且用户名中包含有a)或邮箱为null的用户信息修改 **/
@test
public void test01() {
    /*
        update t_user set user_name=?, email=?
        age > ? and user_name like ? or email is not null
     */
    querywrapper<user> querywrapper = new querywrapper<>();
    querywrapper.gt("age", 20)
            .like("user_name", "a")
            .or()
            .isnotnull("email");
    user user = new user();
    user.setname("小明");
    user.setemail("test@atguigu.com");
    int result = usermapper.update(user, querywrapper);
    system.out.println("result = " + result);
}
/** 条件优先级  将用户名中包含a并且(年龄大于20或邮箱为null)的用户信息修改 **/
@test
public void test02() {
    // lambda中条件优先级
    /*
        update t_user set user_name=?, email=?
        where user_name like ? and (age > ? or email is null)
     */
    querywrapper<user> querywrapper = new querywrapper<>();
    querywrapper.like("user_name", "a")
            .and(i -> i.gt("age", 20).or().isnull("email"));
    user user = new user();
    user.setname("小红");
    user.setemail("test@atguigu.com");
    int result = usermapper.update(user, querywrapper);
    system.out.println("result = " + result);
}

@test
public void test3() {
    /*
        select uid as id,user_name as name,age,email,is_deleted from t_user
        where user_name like ? and age <= ?
     */
    string username = "a";
    integer agebegin = null;
    integer ageend = 30;
    //组装set子句
    lambdaquerywrapper<user> querywrapper = new lambdaquerywrapper<>();
    //避免使用字符串表示字段，防止运行时错误
    querywrapper.like(stringutils.isnotblank(username), user::getname, username)
            .gt(agebegin != null, user::getage, agebegin)
            .le(ageend != null, user::getage, ageend);
    list<user> list = usermapper.selectlist(querywrapper);
    list.foreach(system.out::println);
}
@test
public void test4() {
    /*
        update t_user set user_name=?,email=?
        where user_name like ? and (age > ? or email is null)
     */
    lambdaupdatewrapper<user> updatewrapper = new lambdaupdatewrapper<>();
    updatewrapper.like(user::getname, "a")
            //lambda表达式内的逻辑优先运算
            .and(i -> i.gt(user::getage, 20).or().isnull(user::getemail)); 
    updatewrapper.set(user::getname, "小黑").set(user::getemail, "abc@atguigu.com");
    int result = usermapper.update(null, updatewrapper);
    system.out.println("result = " + result);
}

 @test
 public void test1(){
 	 // 单个查询，多个报错
     user user = userservice.lambdaquery().eq(user::getname, "tom").one();
	 // 集合查询
     list<user> userlist = userservice.lambdaquery().like(user::getname, "j").eq(user::getage,20).list();
     // 记录数查询
     integer count = userservice.lambdaquery().like(user::getage, 20).select(user::getname, user::getage).count();
  }

  @test
  public void test2() {
	  // set修改某些属性
      userservice.lambdaupdate().eq(user::getname, "tom").set(user::getid, 110).set(user::getage, 15).update();
      // 修改整个对象
      user user = new user();
      user.setid(110l);
      user.setage(15);
      userservice.lambdaupdate().eq(user::getname, "tom").update(user);
      // 根据名称删除
      userservice.lambdaupdate().eq(user::getname, "jack").remove();
   }

@test
void testdbget() {
    user user = db.getbyid(1l, user.class);
    system.out.println(user);
}
​
@test
void testdblist() {
    // 利用db实现复杂条件查询
    list<user> list = db.lambdaquery(user.class)
            .like(user::getusername, "o")
            .ge(user::getbalance, 1000)
            .list();
}
​
@test
void testdbupdate() {
    db.lambdaupdate(user.class)
            .set(user::getbalance, 2000)
            .eq(user::getusername, "rose");
}

/**
* 根据年龄查询用户列表，分页显示
*/
page<user> selectpagevo(@param("page") page<user> page,@param("age") integer age);

<select id="selectpagevo" resulttype="user">
    select id,username as name,age,email from t_user where age > #{age}
</select>

@test
public void testselectpagevo(){ //设置分页参数
    page<user> page = new page<>(1, 5); 
    usermapper.selectpagevo(page, 20);
    //获取分页数据
    list<user> list = page.getrecords(); 
    list.foreach(system.out::println); 
    system.out.println("当前页:"+page.getcurrent()); 
    system.out.println("每页显示的条数:"+page.getsize()); 
    system.out.println("总记录数:"+page.gettotal()); 
    system.out.println("总页数:"+page.getpages()); 
    system.out.println("是否有上一页:"+page.hasprevious()); 
    system.out.println("是否有下一页:"+page.hasnext());
}

@select("select * from student where age = #{age} and user_name = #{username}")
student getstudent( @param("age") integer age, @param("username") string username);

// 单表查询
@select("select * from student ${ew.customsqlsegment}")
student getstudentbyid( @param("ew") querywrapper<student> wrapper);
// 多表查询
@select("select u.* from student u inner join address a on u.id = a.student_id ${ew.customsqlsegment}")
list<student> querystudentlistbywrapper(@param("page") page<student> page, @param("ew")querywrapper<user> wrapper);

// 情况1：如果查询条件中有address的字段，比如模糊查询地址名称
// 情况2：如果查询条件的字段，两个表都有，这里会有问题
// 自动分页的查询count(*)时候，就会抛出以上异常
@select("select u.* from student u left join address a on u.id = a.student_id ${ew.customsqlsegment}")
list<student> querystudentlistbywrapper(@param("page") page<student> page, @param("ew")querywrapper<user> wrapper);

@select("select * from (select u.* from student u left join address a on u.id = a.student_id) as result ${ew.customsqlsegment}")
list<student> querystudentlistbywrapper(@param("page") page<student> page, @param("ew")querywrapper<user> wrapper);

// 分页查询
page<userentity> userpage = super.lambdaquery().page(new page<>(request.getcurrent(), request.getsize()));
// entity转换为vo
ipage<uservo> inforespage = userpage.convert(item -> convert.convert(uservo.class, item));

// 方式一
list<string> namelist = simplequery.list(
        new lambdaquerywrapper<student>().like(student::getusername, "张"),
        student::getusername
);
// 方式二
list<student> list = studentservice.list();
list<string> namelist2 = simplequery.list2list(list, student::getusername);

list<string> namelist = simplequery.list(
        new lambdaquerywrapper<student>().like(student::getusername, "李"),
        student::getusername,
        new consumer<student>() {
            @override
            public void accept(student student) {
                student.setusername("**"+student.getusername()+"**");
            }
        }
);

map<string, integer> map = simplequery.map(
        new lambdaquerywrapper<>(), 
        student::getusername, 
        student::getage
);

map<string, list<student>> group = simplequery.group(
        new lambdaquerywrapper<student>(), 
        student::getusername
);

@data
@tablename(value = "student")
public class student extends model<student> {
    /**
     * 主键id
     */
    private long id;
    /**
     * 姓名
     */
    private string username;
    /**
     * 年龄
     */
    private integer age;
}
@test
void activerecordaddq{
	student student = new student();
	student.setusername("李四");
	student.setage(12);
	student.insert();
}

@configuration
public class mybatisplusconfig {
    @bean
    public mybatisplusinterceptor mybatisplusinterceptor() {
        mybatisplusinterceptor interceptor = new mybatisplusinterceptor();
        //注意使用哪种数据库
        interceptor.addinnerinterceptor(new paginationinnerinterceptor(dbtype.mysql));
        return interceptor;
    }
}