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docs: add auto mapper docs
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@ -58,6 +58,7 @@ export default defineConfig({
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items: [
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{text: '增、删、改', link: '/zh/base/add-delete-update'},
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{text: '基础查询', link: '/zh/base/query'},
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{text: '自动映射', link: '/zh/base/auto-mapping'},
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{text: '关联查询', link: '/zh/base/relations-query'},
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{text: '批量操作', link: '/zh/base/batch'},
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{text: '链式操作🔥🔥', link: '/zh/base/chain'},
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251
docs/zh/base/auto-mapping.md
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251
docs/zh/base/auto-mapping.md
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@ -0,0 +1,251 @@
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# 自动映射
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在 MyBatis-Flex 中,内置了非常智能的 **自动映射** 功能,能够使得我们在查询数据的时候,从数据结果集绑定到实体类(或者 VO、DTO等)等变得极其简单易用。
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## 数据假设
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假设在我们的项目中,有如下的表结构、和实体类:
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账户表(tb_account):
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```sql
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CREATE TABLE IF NOT EXISTS `tb_account`
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(
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`id` INTEGER auto_increment,
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`user_name` VARCHAR(100),
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`age` Integer
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);
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```
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图书表(tb_book):
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```sql
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CREATE TABLE IF NOT EXISTS `tb_book`
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(
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`id` INTEGER auto_increment,
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`account_id` Integer,
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`title` VARCHAR(100),
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`content` text
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);
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```
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> 图书和账户的关系是多对一的关系:一个账户可以拥有多本书。
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角色表(tb_role):
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```sql
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CREATE TABLE IF NOT EXISTS `tb_role`
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(
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`id` INTEGER auto_increment,
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`name` VARCHAR(100)
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);
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```
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账户和角色的 **多对多** 关系映射表(tb_role_mapping):
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```sql
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CREATE TABLE IF NOT EXISTS `tb_role_mapping`
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(
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`account_id` INTEGER ,
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`role_id` INTEGER
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);
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```
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## 基础映射
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基础映射指的是,定义的实体类和表结构是一一对应的关系,例如:
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```java
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@Table(value = "tb_account")
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public class Account {
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@Id(keyType = KeyType.Auto)
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private Long id;
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private String userName;
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private int age;
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//getter setter
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}
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```
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`Account.java `与表 `tb_account` 是字段和属性是一一对应关系的。此时,我们在查询数据的时候,可以通过
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`AccountMapper` 方法直接查询,例如:
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```java
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QueryWrapper qw = new QeuryWrapper();
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qw.select(ACCOUNT.ALL_COLUMNS)
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.where(ACCOUNT.ID.ge(100));
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List<Account> accounts = accountMapper.selectListByQuery(qw);
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```
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或者使用如下的链式查询,都可以直接得到 `List<Account>` 结果:`accounts`。
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```java
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QueryChain.of(accountMapper)
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.select(ACCOUNT.ALL_COLUMNS)
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.where(ACCOUNT.ID.ge(100))
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.list();
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```
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## AS 映射
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假设我们在 `Account.java` 中多定义了一些其他属性,如下所示:
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```java
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@Table(value = "tb_account")
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public class Account {
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@Id(keyType = KeyType.Auto)
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private Long id;
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private String userName;
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private int age;
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//最大年龄
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private int maxAge;
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//平均年龄
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private int svgAge;
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//getter setter
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}
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```
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那么,我们在查询的时候,就可以通过 `as` 进行映射关联,查询代码如下:
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```java 4,5
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QueryChain.of(accountMapper)
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.select(
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ACCOUNT.ALL_COLUMNS,
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max(ACCOUNT.AGE).as("maxAge"),
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avg(ACCOUNT.AGE).as("svgAge")
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).where(ACCOUNT.ID.ge(100))
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.list();
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```
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或者:
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```java 4,5
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QueryChain.of(accountMapper)
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.select(
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ACCOUNT.ALL_COLUMNS,
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max(ACCOUNT.AGE).as("max_age"),
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avg(ACCOUNT.AGE).as("svg_age")
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).where(ACCOUNT.ID.ge(100))
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.list();
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```
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或者使用 lambda:
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```java 4,5
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QueryChain.of(accountMapper)
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.select(
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ACCOUNT.ALL_COLUMNS,
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max(ACCOUNT.AGE).as(Account::getMaxAge),
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avg(ACCOUNT.AGE).as(Account::getAvgAge)
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).where(ACCOUNT.ID.ge(100))
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.list();
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```
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## 多表映射
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假设我们定义了一个 `BootVo.java`,其中包含了图书的基本信息,也包含了图书归属的用户信息,例如:
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```java
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public class BookVo {
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//图书的基本字段
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private Long id;
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private Long accountId;
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private String title;
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private String content;
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//用户表的字段
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private String userName;
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private int userAge;
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}
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```
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此时,我们再进行 `left join` 多表查询时,代码如下:
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```java
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List<BookVo> bookVos = QueryChain.of(bookMapper)
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.select(
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BOOK.ALL_COLUMNS, //图书的所有字段
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ACCOUNT.USER_NAME, //用户表的 user_name 字段
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ACCOUNT.AGE.as("userAge") //用户表的 age 字段, as "userAge"
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).form(BOOK)
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.leftJoin(ACCONT).on(BOOK.ACCOUNT_ID.eq(ACCOUNT.ID))
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.where(ACCOUNT.ID.ge(100))
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.listAs(BookVo.java);
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```
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或者,我们也可以直接在 BookVo 中,定义 `Account` 对象,例如:
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```java
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public class BookVo {
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//图书的基本字段
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private Long id;
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private Long accountId;
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private String title;
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private String content;
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//用户
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private Account account;
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}
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```
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查询代码如下:
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```java
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List<BookVo> bookVos = QueryChain.of(bookMapper)
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.select(
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BOOK.DEFAULT_COLUMNS,
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ACCOUNT.DEFAULT_COLUMNS,
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)
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.form(BOOK)
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.leftJoin(ACCONT).on(BOOK.ACCOUNT_ID.eq(ACCOUNT.ID))
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.where(ACCOUNT.ID.ge(100))
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.listAs(BookVo.java);
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```
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## 高级映射
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在以上的表结构中,一个账户可以有多本图书,那么我们假设定义的 `AccountVo.java` 的结构如下:
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```java
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public class AccountVO {
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private Long id;
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private String userName;
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private int age;
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//账户拥有的 图书列表
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private List<Book> books;
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}
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```
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```java
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List<AccountVO> bookVos = QueryChain.of(accountMapper)
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.select() // 不传入参数等同于 SQL 的 select *
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.form(ACCONT)
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.leftJoin(BOOK).on(ACCOUNT.ID.eq(BOOK.ACCOUNT_ID))
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.where(ACCOUNT.ID.ge(100))
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.listAs(AccountVO.java);
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```
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亦或者指定查询参数:
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```java
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List<AccountVO> bookVos = QueryChain.of(accountMapper)
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.select(
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ACCOUNT.ID,
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ACCOUNT.USER_NAME,
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ACCOUNT.AGE,
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BOOK.TITLE,
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BOOK.CONTENT,
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)
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.form(ACCONT)
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.leftJoin(BOOK).on(ACCOUNT.ID.eq(BOOK.ACCOUNT_ID))
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.where(ACCOUNT.ID.ge(100))
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.listAs(AccountVO.java);
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```
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高级映射的场景中,我们还可以通过注解 `@RelationManyToOne` 进行查询,
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详情请点击 [这里](./relations-query#%E4%B8%80%E5%AF%B9%E5%A4%9A-relationonetomany)。
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@ -203,7 +203,7 @@ WHERE account_id IN (1, 2, 3, 4, 5)
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**Map 映射**
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若 `Account.books` 是一个 `Map`,而非 `List`,那么,我们需要通过配置 `mapKeyField` 来指定使用用个列来充当 `Map` 的 `Key`,
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若 `Account.books` 是一个 `Map`,而非 `List`,那么,我们需要通过配置 `mapKeyField` 来指定使用 `Book` 的那个列来充当 `Map` 的 `Key`,
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如下代码所示:
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```java 9
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@ -218,6 +218,11 @@ public class Account implements Serializable {
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, mapKeyField = "id") //使用 Book 的 id 来填充这个 map 的 key
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private Map<Long, Book> books;
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//注意 map 的 key 的类型,可以和 Book 的 id 类型不一致也是支持的
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//比如:
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//private Map<String, Book> books;
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//getter setter
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}
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```
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