纯代码测试mybatis的xml语句，无需修改mybatis配置文件

背景：有时候需要测试xml中的sql写的对不对，重启整个系统比较慢。

一般的方式是：

  （1）创建mybatis-config.xml，里面配置datasource，然后配置要测试的sql所在xml

 （2）然后再通过mybatis自带的方式获取它的SqlSessionFactory 和sqlSession 

import org.apache.ibatis.datasource.pooled.PooledDataSource;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.mapping.Environment;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.apache.ibatis.transaction.TransactionFactory;
import org.apache.ibatis.transaction.jdbc.JdbcTransactionFactory;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.core.io.support.ResourcePatternResolver;

import javax.sql.DataSource;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class MybatisTest {
     @Before
    public void beforeTest() throws IOException {
        System.out.println("-------------------------------before----------------------------");
        // 创建数据源
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        sqlSession = sqlSessionFactory.openSession(true);
    }
    @After
    public void after(){
        System.out.println("-------------------------------after----------------------------");
        sqlSession.close();
    }
     @Test
    public void testMybatis() throws IOException {
         UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        Map params = new HashMap<>();
         params.put("XX",1001);
        System.out.println(mapper.query(params));
    }
}

mybatis-config.xml

其实也挺方便的，但还是很烦，每次要去mybatis-config.xml里面去加 xml！！！

借鉴springboot中对mapperLocations的处理：

改进后的方法：

import org.apache.ibatis.datasource.pooled.PooledDataSource;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.mapping.Environment;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.apache.ibatis.transaction.TransactionFactory;
import org.apache.ibatis.transaction.jdbc.JdbcTransactionFactory;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.core.io.support.ResourcePatternResolver;

import javax.sql.DataSource;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class MybatisTest {
    SqlSession sqlSession;
    DataSource dataSource;

    private void setDataSource(){
        // 创建数据源
         dataSource = new PooledDataSource("org.postgresql.Driver",
                "jdbc:postgresql://xxxx",
                "xx",
                "xxx");
}

     public Resource[] resolveMapperLocations(String[] mapperLocations) {
        ResourcePatternResolver resourceResolver = new PathMatchingResourcePatternResolver();
        List resources = new ArrayList();
        if (mapperLocations != null) {
            for (String mapperLocation : mapperLocations) {
                try {
                    Resource[] mappers = resourceResolver.getResources(mapperLocation);
                    resources.addAll(Arrays.asList(mappers));
                } catch (IOException e) {
                    // ignore
                }
            }
        }
        return resources.toArray(new Resource[resources.size()]);
    }

    @Before
    public void beforeTestSpring() throws Exception {
        System.out.println("-------------------------------before222----------------------------");
        // 创建数据源
        setDataSource();
        SqlSessionFactoryBean sqlSessionFactoryBean  = new SqlSessionFactoryBean();
        org.springframework.core.io.Resource[]   resources = resolveMapperLocations(new String[]{"mappers/com/xxxx/*.xml"});
        sqlSessionFactoryBean.setMapperLocations(resources);
        sqlSessionFactoryBean.setDataSource(dataSource);
        SqlSessionFactory sqlSessionFactory =   sqlSessionFactoryBean.getObject();
        sqlSession =  sqlSessionFactory.openSession(true);

    }
    @After
    public void after(){
        System.out.println("----------after-------------");
        sqlSession.close();
    }

     @Test
    public void testMybatis() throws IOException {
         UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        Map params = new HashMap<>();
         params.put("XX",1001);
        System.out.println(mapper.query(params));
    }

}

这样的好处就是：

（1）配一个mapperLocation就好了，不用再去一个个配sql的xml位置。

（2）springboot单元测试也可以做测试，但是会启动所有的bean，扫描所有xml，这样不用依赖spring启动，只要有spring环境即可，同时又避免了springboot整个启动，扫描所有xml。