目录
1、Wrapper 介绍
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Wrapper ： 条件构造抽象类，最顶端父类
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AbstractWrapper ： 用于查询条件封装，生成 sql 的 where 条件
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QueryWrapper ： 查询条件封装
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UpdateWrapper ： Update 条件封装
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AbstractLambdaWrapper ： 使用Lambda 语法
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LambdaQueryWrapper ：用于Lambda语法使用的查询Wrapper
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LambdaUpdateWrapper ： Lambda 更新封装Wrapper
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2、QueryWrapper
2.1、组装查询条件
测试方法：
@Test
public void test01(){
// 查询用户名包含a，年龄在20到30之间，邮箱不为null的用户信息
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.like("user_name", "a")
.between("age", 20, 30)
.isNotNull("email");
// SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 AND (user_name LIKE ? AND age BETWEEN ? AND ? AND email IS NOT NULL)
List<User> users = userMapper.selectList(queryWrapper);
users.forEach(System.out::println);
}输出结果：
==> Preparing: SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 AND (user_name LIKE ? AND age BETWEEN ? AND ? AND email IS NOT NULL)
==> Parameters: %a%(String), 20(Integer), 30(Integer)
<== Columns: id, name, age, email, is_deleted
<== Row: 2, Jack, 20, [email protected], 0
<== Row: 4, Sandy, 21, [email protected], 0
<== Total: 2
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@75361cf6]
User(id=2, name=Jack, age=20, [email protected], isDeleted=0)
User(id=4, name=Sandy, age=21, [email protected], isDeleted=0)2.2、组装排序条件
测试方法：
@Test
public void test02(){
// 查询用户信息，按照年龄降序排序，若年龄相同，按照uid升序排序
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.orderByDesc("age").orderByAsc("uid");
// SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 ORDER BY age DESC,uid ASC
List<User> users = userMapper.selectList(queryWrapper);
users.forEach(System.out::println);
}输出结果：
==> Preparing: SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 ORDER BY age DESC,uid ASC
==> Parameters:
<== Columns: id, name, age, email, is_deleted
<== Row: 6, 王五, 46, [email protected], 0
<== Row: 7, 王五, 46, [email protected], 0
<== Row: 8, 王五, 46, [email protected], 0
<== Row: 3, Tom, 28, [email protected], 0
<== Row: 5, Billie, 24, [email protected], 0
<== Row: 4, Sandy, 21, [email protected], 0
<== Row: 2, Jack, 20, [email protected], 0
<== Row: 1, Jone, 18, [email protected], 0
<== Total: 8
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@43d38654]
User(id=6, name=王五, age=46, [email protected], isDeleted=0)
User(id=7, name=王五, age=46, [email protected], isDeleted=0)
User(id=8, name=王五, age=46, [email protected], isDeleted=0)
User(id=3, name=Tom, age=28, [email protected], isDeleted=0)
User(id=5, name=Billie, age=24, [email protected], isDeleted=0)
User(id=4, name=Sandy, age=21, [email protected], isDeleted=0)
User(id=2, name=Jack, age=20, [email protected], isDeleted=0)
User(id=1, name=Jone, age=18, [email protected], isDeleted=0)2.3、组装删除条件
测试方法：
@Test
public void test03(){
// 删除邮箱为[email protected]的用户
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.eq("email", "[email protected]");
// UPDATE t_user SET is_deleted=1 WHERE is_deleted=0 AND (email = ?)
int ret = userMapper.delete(queryWrapper);
System.out.println("ret = " + ret);
}输出结果：
==> Preparing: UPDATE t_user SET is_deleted=1 WHERE is_deleted=0 AND (email = ?)
==> Parameters: [email protected](String)
<== Updates: 32.4、使用QueryWrapper实现修改功能
测试方法：
@Test
public void test04(){
// 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
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.gt("age", 20)
.like("user_name", "a")
.or()
.isNull("email");
User user = new User();
user.setName("小明");
user.setEmail("[email protected]");
// UPDATE t_user SET user_name=?, email=? WHERE is_deleted=0 AND (age > ? AND user_name LIKE ? OR email IS NULL)
int ret = userMapper.update(user, queryWrapper);
System.out.println("ret = " + ret);
}输出结果：
==> Preparing: UPDATE t_user SET user_name=?, email=? WHERE is_deleted=0 AND (age > ? AND user_name LIKE ? OR email IS NULL)
==> Parameters: 小明(String), [email protected](String), 20(Integer), %a%(String)
<== Updates: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@a518813]
ret = 12.5、条件的优先级：使用lambda表达式
例如以下两种情况
@Test
public void test04(){
// 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
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.gt("age", 20)
.like("user_name", "a")
.or()
.isNull("email");
User user = new User();
user.setName("小明");
user.setEmail("[email protected]");
// UPDATE t_user SET user_name=?, email=? WHERE is_deleted=0 AND (age > ? AND user_name LIKE ? OR email IS NULL)
int ret = userMapper.update(user, queryWrapper);
System.out.println("ret = " + ret);
} @Test
public void test05(){
// 将用户名中包含有a并且(年龄大于20或邮箱为null)的用户信息修改
// lambda中的条件优先执行
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("[email protected]");
// UPDATE t_user SET user_name=?, email=? WHERE is_deleted=0 AND (user_name LIKE ? AND (age > ? OR email IS NULL))
int ret = userMapper.update(user, queryWrapper);
System.out.println("ret = " + ret);
}2.6、组装 select 语句：仅查询需要的字段
测试方法：
@Test
public void test06(){
// 查询用户的用户名、年龄、邮箱信息
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.select("user_name", "age", "email");
// SELECT user_name,age,email FROM t_user WHERE is_deleted=0
List<Map<String, Object>> maps = userMapper.selectMaps(queryWrapper);
maps.forEach(System.out::println);
}输出结果：
==> Preparing: SELECT user_name,age,email FROM t_user WHERE is_deleted=0
==> Parameters:
<== Columns: user_name, age, email
<== Row: Jone, 18, [email protected]
<== Row: Jack, 20, [email protected]
<== Row: Tom, 28, [email protected]
<== Row: 小明, 21, [email protected]
<== Row: Billie, 24, [email protected]
<== Row: 小红, null, [email protected]
<== Total: 6
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@790a251b]
{user_name=Jone, age=18, [email protected]}
{user_name=Jack, age=20, [email protected]}
{user_name=Tom, age=28, [email protected]}
{user_name=小明, age=21, [email protected]}
{user_name=Billie, age=24, [email protected]}
{user_name=小红, [email protected]}2.7、实现子查询
测试方法：
@Test
public void test07(){
// 子查询： 查询id小于等于100的用户信息
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.inSql("uid", "select uid from t_user where uid <= 100");
// SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 AND (uid IN (select uid from t_user where uid <= 100))
List<User> users = userMapper.selectList(queryWrapper);
users.forEach(System.out::println);
}输出结果：
==> Preparing: SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 AND (uid IN (select uid from t_user where uid <= 100))
==> Parameters:
<== Columns: id, name, age, email, is_deleted
<== Row: 1, Jone, 18, [email protected], 0
<== Row: 2, Jack, 20, [email protected], 0
<== Row: 3, Tom, 28, [email protected], 0
<== Row: 4, 小明, 21, [email protected], 0
<== Row: 5, Billie, 24, [email protected], 0
<== Row: 9, 小红, null, [email protected], 0
<== Total: 6
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@2dfe5525]
User(id=1, name=Jone, age=18, [email protected], isDeleted=0)
User(id=2, name=Jack, age=20, [email protected], isDeleted=0)
User(id=3, name=Tom, age=28, [email protected], isDeleted=0)
User(id=4, name=小明, age=21, [email protected], isDeleted=0)
User(id=5, name=Billie, age=24, [email protected], isDeleted=0)
User(id=9, name=小红, age=null, [email protected], isDeleted=0)3、UpdateWrapper
测试方法：
@Test
public void test08(){
// 将用户名中包含有a并且(年龄大于20或邮箱为null)的用户信息修改
UpdateWrapper<User> updateWrapper = new UpdateWrapper<>();
updateWrapper.like("user_name", "a")
.and(i -> i.gt("age", 20).or().isNull("email"));
updateWrapper.set("user_name", "小黑").set("email", "[email protected]");
// UPDATE t_user SET user_name=?,email=? WHERE is_deleted=0 AND (user_name LIKE ? AND (age > ? OR email IS NULL))
int ret = userMapper.update(null, updateWrapper);
System.out.println("ret = " + ret);
}输出结果：
==> Preparing: UPDATE t_user SET user_name=?,email=? WHERE is_deleted=0 AND (user_name LIKE ? AND (age > ? OR email IS NULL))
==> Parameters: 小黑(String), [email protected](String), %a%(String), 20(Integer)
<== Updates: 0
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@55d9b8f0]
ret = 04、模拟开发中组装条件的情况
在真正开发的过程中，组装条件是常见的功能，而这些条件数据来源于用户输入，是可选的，因此我们在组装这些条件时，必须先判断用户是否选择了这些条件，若选择则需要组装该条件，若没有选择则一定不能组装，以免影响SQL执行的结果
4.1、思路一：使用 if 语句判断
@Test
public void test09(){
// 模拟开发中组装条件的情况，思路一：if语句判断，较麻烦
String username = "a";
Integer ageBegin = null;
Integer ageEnd = 30;
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
if(StringUtils.isNotBlank(username)){
// isNotBlank：判断某个字符串是否不为空字符串、不为null、不为空白符
queryWrapper.like("user_name", username);
}
if(ageBegin != null){
queryWrapper.ge("age",ageBegin);
}
if(ageEnd != null){
queryWrapper.le("age", ageEnd);
}
// SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 AND (user_name LIKE ? AND age <= ?)
List<User> users = userMapper.selectList(queryWrapper);
users.forEach(System.out::println);
}4.2、思路二：利用 condition
@Test
public void test10(){
// 模拟开发中组装条件的情况：使用condition
String username = "a";
Integer ageBegin = null;
Integer ageEnd = 30;
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
// isNotBlank：判断某个字符串是否不为空字符串、不为null、不为空白符
queryWrapper.like(StringUtils.isNotBlank(username), "user_name", username)
.ge(ageBegin != null, "age", ageBegin)
.le(ageEnd != null, "age", ageEnd);
// SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 AND (user_name LIKE ? AND age <= ?)
List<User> users = userMapper.selectList(queryWrapper);
users.forEach(System.out::println);
}5、LambdaQueryWrapper
@Test
public void test11(){
String username = "a";
Integer ageBegin = null;
Integer ageEnd = 30;
LambdaQueryWrapper<User> lambdaQueryWrapper = new LambdaQueryWrapper<User>();
// LambdaQueryWrapper中使用的是lambda的函数式接口
lambdaQueryWrapper.like(StringUtils.isNotBlank(username), User::getName, username)
.ge(ageBegin != null, User::getAge, ageBegin)
.le(ageEnd != null, User::getAge, ageEnd);
// SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 AND (user_name LIKE ? AND age <= ?)
List<User> users = userMapper.selectList(lambdaQueryWrapper);
users.forEach(System.out::println);
}6、LambdaUpdateWrapper
@Test
public void test12(){
// 将用户名中包含有a并且(年龄大于20或邮箱为null)的用户信息修改
LambdaUpdateWrapper<User> lambdaUpdateWrapper = new LambdaUpdateWrapper<>();
lambdaUpdateWrapper.like(User::getName, "a")
.and(i -> i.gt(User::getAge, 20).or().isNull(User::getEmail));
lambdaUpdateWrapper.set(User::getName, "小黑").set(User::getEmail, "[email protected]");
// UPDATE t_user SET user_name=?,email=? WHERE is_deleted=0 AND (user_name LIKE ? AND (age > ? OR email IS NULL))
int ret = userMapper.update(null, lambdaUpdateWrapper);
System.out.println("ret = " + ret);
}