Mybatis3中方法返回生成的主键:XML,@SelectKey,@Options详解

需求

在很多业务场景中，我们希望插入一条记录时就返回该记录的相关信息，返回主键显得尤为重要。

解决方案

1、XML中配置

在定义xml映射器时设置属性useGeneratedKeys值为true，并分别指定属性keyProperty和keyColumn为对应的数据库记录主键字段与Java对象的主键属性。

自增主键

<insert id="insert" parameterType="com.xzbd.User" useGeneratedKeys=”true” keyProperty=”id”>
　　insert into user (username,password,email,bio) values (#{username},#{password},#{email},#{bio})
</insert>

使用标签selectKey和select LAST_INSERT_ID()

　　 <!-- mysql的自增ID ：LAST_INSERT_ID -->
    <insert id="inserUser2" parameterType="com.xzbd.User" >
        <selectKey keyProperty="user_id" order="AFTER" resultType="java.lang.Integer">
            select LAST_INSERT_ID()
        </selectKey> 
        insert into t_user(name,age) value(#{name},#{age})
    </insert>

非自增，UUID

    <insert id="inserUser4" parameterType="com.xzbd.User" >
        <selectKey keyProperty="user_id" order="AFTER" resultType="java.lang.Integer">
            select uuid()
        </selectKey>
        insert into t_user(user_id,name,age) value(#{user_id},#{name},#{age})
    </insert>

2、Mapper中使用@SelectKey或@Options注解配置

@SelectKey注解的功能与 <selectKey>标签完全一致，用在已经被@Insert 、@InsertProvider 或 @Update 、@UpdateProvider 注解了的方法上。

在未被上述四个注解的方法上作 @SelectKey 注解则视为无效。

如果你指定了 @SelectKey注解，那么 MyBatis 就会忽略掉由 @Options 注解所设置的生成主键或设置（configuration）属性,即@SelectKey与 @Options不应同时使用。

• @SelectKey

示例如下：

@Insert("insert into user (name) values(#{name})")  
@SelectKey(statement="select LAST_INSERT_ID()", keyProperty="id", before=false, resultType=int.class)  
int insert(String name);

• @Options

该注解能更精细化的控制SQL执行，其代码如下：

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD})
public @interface Options {
    boolean useCache() default true;
    boolean flushCache() default false;
    ResultSetType resultSetType() default ResultSetType.FORWARD_ONLY;
    StatementType statementType() default StatementType.PREPARED;
    int fetchSize() default -1;
    int timeout() default -1;
    boolean useGeneratedKeys() default false;
    String keyProperty() default "id";
    String keyColumn() default "";
}

示例如下：

    @InsertProvider(type = SqlProviderAdapter.class, method = "insert")
    @SelectKey(
            keyProperty = "record.id", before = false,
            resultType = Long.class,statement = {"select last_insert_id()"}
    )
    int insert(InsertStatementProvider<User> insertStatement);

3、特别案例MyBatis Dynamic SQL

官方文档中Insert Statements描述如下

MyBatis supports returning generated values from a single row insert, or a batch insert. In either case, it is simply a matter of configuring the insert mapper method appropriately. For example, to retrieve the value of a calculated column configure your mapper method like this:

...
    @InsertProvider(type=SqlProviderAdapter.class, method="insert")
    @Options(useGeneratedKeys=true, keyProperty="row.fullName")
    int insert(InsertStatementProvider<GeneratedAlwaysRecord> insertStatement);
...

The important thing is that the keyProperty is set correctly. It should always be in the form row. where is the attribute of the record class that should be updated with the generated value.

注意

keyProperty="row.fullName” 中的row不一定正确，按照这个写后，会报错

org.apache.ibatis.executor.ExecutorException: No setter found for the keyProperty 'xxx' in …… DefaultInsertStatementProvider

的异常，改为 keyProperty="fullName“ 也会报异常，通过查看 DefaultInsertStatementProvider 源码

最终通过代码为

keyProperty="rocord.fullName” 

4、批量插入

批量插入和单条插入差不多， MyBatis Dynamic SQL批量插入案例如下。

MyBatis supports returning generated values from a multiple row insert statement with some limitations.

The main limitation is that MyBatis does not support nested lists in parameter objects.

Unfortunately, the MultiRowInsertStatementProvider relies on a nested List.

It is likely this limitation in MyBatis will be removed at some point in the future, so stay tuned.

Nevertheless, you can configure a mapper that will work with the MultiRowInsertStatementProvider as created by this library.

The main idea is to decompose the statement from the parameter map and send them as separate parameters to the MyBatis mapper. For example:

...
    @InsertProvider(type=SqlProviderAdapter.class, method="insertMultipleWithGeneratedKeys")
    @Options(useGeneratedKeys=true, keyProperty="records.fullName")
    int insertMultipleWithGeneratedKeys(String insertStatement, @Param("records") List<GeneratedAlwaysRecord> records);

    default int insertMultipleWithGeneratedKeys(MultiRowInsertStatementProvider<GeneratedAlwaysRecord> multiInsert) {
        return insertMultipleWithGeneratedKeys(multiInsert.getInsertStatement(), multiInsert.getRecords());
    }
...

The first method above shows the actual MyBatis mapper method.

Note the use of the @Options annotation to specify that we expect generated values.

Further, note that the keyProperty is set to records.fullName - in this case, fullName is a property of the objects in the records List.

The library supplied adapter method will simply return the insertStatement as supplied in the method call.

The adapter method requires that there be one, and only one, String parameter in the method call, and it assumes that this one String parameter is the SQL insert statement.

The parameter can have any name and can be specified in any position in the method’s parameter list.

The @Param annotation is not required for the insert statement. However, it may be specified if you so desire.

The second method above decomposes the MultiRowInsertStatementProvider and calls the first method.

结论

以上为个人经验，希望能给大家一个参考，也希望大家多多支持脚本之家。