Mybatis - 自定义BaseMapper SQLProvider篇

SQL Provider

• @InsertProvider
• @UpdateProvider
• @DeleteProvider
• @SelectProvider

这些可选的SQL注解允许你指定一个类名和一个方法，在执行时来返回动态的SQL。

@SelectProvider(type = UserSqlBuilder.class, method = "buildGetUsersByName")
List getUsersByName(String name);

class UserSqlBuilder {
    public String buildGetUsersByName(final String name) {
        return new SQL(){{
            SELECT("*");
            FROM("users");
            if (name != null) {
                WHERE("name like #{value} || '%'");
            }
            ORDER_BY("id");
        }}.toString();
    }
}

BaseMapper

我们可以使用 SQLProvider 构建属于自己的BaseMapper。

public interface BaseMapper {
    @InsertProvider(type = SqlSourceBuilder.class, method = "build")
    public Long insert(T model);

    @UpdateProvider(type = SqlSourceBuilder.class, method = "build")
    public Long updateById(T model);

    @DeleteProvider(type = SqlSourceBuilder.class, method = "build")
    public Long deleteById(@Param("id") K id);

    @SelectProvider(type = SqlSourceBuilder.class, method = "build")
    public T getById(@Param("id") K id);

    @SelectProvider(type = SqlSourceBuilder.class, method = "build")
    public Boolean existById(@Param("id") K id);
}

SqlSourceBuilder

把用SQLProvider生成的ProviderSqlSource替换成DynamicSqlSource

public class SqlSourceBuilder {
    public static String build(Configuration configuration) {
        for (MappedStatement mappedStatement : configuration.getMappedStatements()) {
            if (mappedStatement.getSqlSource() instanceof ProviderSqlSource) {
                Class providerClass = getProviderClass(mappedStatement);
                if (providerClass != SqlSourceBuilder.class)
                    continue;

                Class mapperClass = getMapperClass(mappedStatement);
                Class[] generics = getMapperGenerics(mapperClass);
                Class modelClass = generics[0];
                Class primaryFieldClass = generics[1];
                ResultMap resultMap = getResultMap(mappedStatement, modelClass);

                String sqlScript = getSqlScript(mappedStatement, mapperClass, modelClass, primaryFieldClass, resultMap);
                SqlSource sqlSource = createSqlSource(mappedStatement, sqlScript);
                setSqlSource(mappedStatement, sqlSource);
            }
        }
        return "sql";
    }
    ...
}

MapperTest 测试

public class MapperTest {
    @Test
    public void test() throws Exception {
        SqlSessionFactory sessionFactory = MybatisConfig.getSessionFactory();
        SqlSession session = sessionFactory.openSession();

        UserMapper userMapper = session.getMapper(UserMapper.class);

        User user = null;

        // 新增测试
        System.out.println("------------ 新增测试 ------------");
        user = new User();
        user.setId(1L);
        user.setAccount("conanli");
        user.setPassword("123456");
        System.out.println("insert: " + userMapper.insert(user));

        // 更新测试
        System.out.println("------------ 更新测试 ------------");
        user = new User();
        user.setId(1L);
        user.setPassword("111111");
        System.out.println("update: " + userMapper.updateById(user));

        // 获取测试
        System.out.println("------------ 获取测试 ------------");
        System.out.println("user: " + userMapper.getById(1L));

        // 删除测试
        System.out.println("------------ 删除测试 ------------");
        System.out.println("delete: " + userMapper.deleteById(1L));

        // 存在测试
        System.out.println("------------ 存在测试 ------------");
        System.out.println("exist: " + userMapper.existById(1L));

        session.commit();
        session.close();
    }
}

完整示例：GitHub
PS：本文使用的是mybatis-3.4.4