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MyBatis 批量更新

很多人在用 MyBatis 或者通用 Mapper 时，经常会问有没有批量插入和批量更新的方法。

实际上许多时候没必要用 <foreach> 去实现特别复杂的批量操作。直接通过 MyBatis 的 BATCH 方式执行增删改方法即可。

下面是一个批量用法的例子：

@Autowired
private SqlSessionFactory sqlSessionFactory;

@Transactional(rollbackFor = Exception.class)
@Override
public void batchTest() {
    SqlSession sqlSession = sqlSessionFactory.openSession(ExecutorType.BATCH);
    CountryMapper mapper = sqlSession.getMapper(CountryMapper.class);
    List<Country> countries = mapper.selectAll();
    for (int i = 0; i < countries.size(); i++) {
        Country country = countries.get(i);
        country.setCountryname(country.getCountryname() + "Test");
        mapper.updateByPrimaryKey(country);
        //每 50 条提交一次
        if((i + 1) % 50 == 0){
            sqlSession.flushStatements();
        }
    }
}

在上面例子中，在 Service 中直接注入了 SqlSessionFactory ，通过下面方法获取了一个可以批量提交的 SqlSession ：

SqlSession sqlSession = sqlSessionFactory.openSession(ExecutorType.BATCH);

后续通过 SqlSession 直接执行方法，或者获取的 Mapper 接口，都使用的批量提交方式。

上述代码执行过程中输出的日志如下：

DEBUG - Creating new transaction with name [com.isea533.mybatis.service.impl.CountryServiceImpl.batchTest]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT
DEBUG - Acquired Connection [com.alibaba.druid.proxy.jdbc.ConnectionProxyImpl@752c11a2] for JDBC transaction
DEBUG - Switching JDBC Connection [com.alibaba.druid.proxy.jdbc.ConnectionProxyImpl@752c11a2] to manual commit
DEBUG - JDBC Connection [com.alibaba.druid.proxy.jdbc.ConnectionProxyImpl@752c11a2] will be managed by Spring
DEBUG - ==>  Preparing: SELECT Id,countryname,countrycode FROM country 
DEBUG - ==> Parameters: 
DEBUG - <==      Total: 183
DEBUG - ==>  Preparing: UPDATE country SET Id = Id,countryname = ?,countrycode = ? WHERE Id = ? 
DEBUG - ==> Parameters: AngolaTest(String), AO(String), 1(Integer)
DEBUG - ==> Parameters: AfghanistanTest(String), AF(String), 2(Integer)
DEBUG - ==> Parameters: AlbaniaTest(String), AL(String), 3(Integer)
==========================================
...省略中间部分参数
==========================================
DEBUG - ==> Parameters: EthiopiaTest(String), ET(String), 50(Integer)
DEBUG - ==>  Preparing: UPDATE country SET Id = Id,countryname = ?,countrycode = ? WHERE Id = ? 
DEBUG - ==> Parameters: FijiTest(String), FJ(String), 51(Integer)
DEBUG - ==> Parameters: FinlandTest(String), FI(String), 52(Integer)
==========================================
...省略中间部分参数
==========================================
DEBUG - ==> Parameters: MadagascarTest(String), MG(String), 98(Integer)
DEBUG - ==> Parameters: MalawiTest(String), MW(String), 99(Integer)
DEBUG - ==> Parameters: MalaysiaTest(String), MY(String), 100(Integer)
DEBUG - ==>  Preparing: UPDATE country SET Id = Id,countryname = ?,countrycode = ? WHERE Id = ? 
DEBUG - ==> Parameters: MaldivesTest(String), MV(String), 101(Integer)
DEBUG - ==> Parameters: MaliTest(String), ML(String), 102(Integer)
==========================================
...省略中间部分参数
==========================================
DEBUG - ==> Parameters: South AfricaTest(String), ZA(String), 149(Integer)
DEBUG - ==> Parameters: SpainTest(String), ES(String), 150(Integer)
DEBUG - ==>  Preparing: UPDATE country SET Id = Id,countryname = ?,countrycode = ? WHERE Id = ? 
DEBUG - ==> Parameters: Sri LankaTest(String), LK(String), 151(Integer)
DEBUG - ==> Parameters: St.LuciaTest(String), LC(String), 152(Integer)
==========================================
...省略中间部分参数
==========================================
DEBUG - ==> Parameters: ZaireTest(String), ZR(String), 182(Integer)
DEBUG - ==> Parameters: ZambiaTest(String), ZM(String), 183(Integer)
==========================================
下面事务自动提交
==========================================
DEBUG - Initiating transaction commit
DEBUG - Committing JDBC transaction on Connection [com.alibaba.druid.proxy.jdbc.ConnectionProxyImpl@752c11a2]
DEBUG - Releasing JDBC Connection [com.alibaba.druid.proxy.jdbc.ConnectionProxyImpl@752c11a2] after transaction
DEBUG - Returning JDBC Connection to DataSource