mybatis 使用自定义sql 语句[通俗易懂]

大家好，我是考100分的小小码，祝大家学习进步，加薪顺利呀。今天说一说mybatis 使用自定义sql 语句[通俗易懂],希望您对编程的造诣更进一步.

新建一个接口 SqlBaseMapper 封装常用的增删改查

public interface SqlBaseMapper {

    /**
     * 查询单条数据返回Map<String, Object>
     *
     * @param sql sql语句
     * @return Map<String, Object>
     */
    Map<String, Object> sqlSelectOne(String sql);

    /**
     * 查询单条数据返回Map<String, Object>
     *
     * @param sql   sql语句
     * @param value 参数
     * @return Map<String, Object>
     */
    Map<String, Object> sqlSelectOne(String sql, Object value);

    /**
     * 查询单条数据返回实体类型
     *
     * @param sql        sql语句
     * @param resultType 具体类型
     * @return 定义的实体类型
     */
    <T> T sqlSelectOne(String sql, Class<T> resultType);

    /**
     * 查询单条数据返回实体类型
     *
     * @param sql        sql语句
     * @param value      参数
     * @param resultType 具体类型
     * @return 定义的实体类型
     */
    <T> T sqlSelectOne(String sql, Object value, Class<T> resultType);

    /**
     * 查询数据返回
     *
     * @param sql sql语句
     * @return List<Map < String, Object>>
     */
    List<Map<String, Object>> sqlSelectList(String sql);

    /**
     * 查询数据返回
     *
     * @param sql   sql语句
     * @param value 参数
     * @return List<Map < String, Object>>
     */
    List<Map<String, Object>> sqlSelectList(String sql, Object value);

    /**
     * 查询数据返回
     *
     * @param sql        sql语句
     * @param resultType 具体类型
     * @return List<T>
     */
    <T> List<T> sqlSelectList(String sql, Class<T> resultType);

    /**
     * 查询数据返回
     *
     * @param sql        sql语句
     * @param value      参数
     * @param resultType 具体类型
     * @return List<T>
     */
    <T> List<T> sqlSelectList(String sql, Object value, Class<T> resultType);

    /**
     * 插入数据
     *
     * @param sql sql语句
     * @return int
     */
    int sqlInsert(String sql);

    /**
     * 插入数据
     *
     * @param sql   sql语句
     * @param value 参数
     * @return int
     */
    int sqlInsert(String sql, Object value);

    /**
     * 更新数据
     *
     * @param sql sql语句
     * @return int
     */
    int sqlUpdate(String sql);

    /**
     * 更新数据
     *
     * @param sql   sql语句
     * @param value 参数
     * @return int
     */
    int sqlUpdate(String sql, Object value);

    /**
     * 删除数据
     *
     * @param sql sql语句
     * @return int
     */
    int sqlDelete(String sql);

    /**
     * 查询数据返回List<T>
     *
     * @param sql   sql语句
     * @param value 参数
     * @return int
     */
    int sqlDelete(String sql, Object value);


}

代码100分

新建一个SqlMapper 实现SqlBaseMapper接口

代码100分/**
 * @author chaild
 * @Date 2020-7-7 14:43:35
 * 自定义SQL查询类
 */
@Component
public class SqlMapper implements SqlBaseMapper {

    /**
     * 使用方式
     *
     * @Autowired private SqlMapper sqlMapper;
     */
    private SqlSession sqlSession;
    private SqlMapper.MSUtils msUtils;

    @Autowired
    SqlSessionFactory sqlSessionFactory;

    public SqlMapper() {
    }

/**这个注解具体意思可以自己去了解一下**/
    @PostConstruct
    private void init() {
        this.sqlSession = sqlSessionFactory.openSession(true);
        this.msUtils = new SqlMapper.MSUtils(sqlSession.getConfiguration());
    }

    private <T> T getOne(List<T> list) {
        if (list.size() == 1) {
            return list.get(0);
        } else if (list.size() > 1) {
            throw new TooManyResultsException("Expected one result (or null) to be returned by selectOne(), but found: " + list.size());
        } else {
            return null;
        }
    }

    /**
     * 查询单条数据返回Map<String, Object>
     *
     * @param sql sql语句
     * @return Map<String, Object>
     */
    @Override
    public Map<String, Object> sqlSelectOne(String sql) {
        List<Map<String, Object>> list = this.sqlSelectList(sql);
        return (Map) this.getOne(list);
    }

    /**
     * 查询单条数据返回Map<String, Object>
     *
     * @param sql   sql语句
     * @param value 参数
     * @return Map<String, Object>
     */
    @Override
    public Map<String, Object> sqlSelectOne(String sql, Object value) {
        List<Map<String, Object>> list = this.sqlSelectList(sql, value);
        return (Map) this.getOne(list);
    }

    /**
     * 查询单条数据返回实体类型
     *
     * @param sql        sql语句
     * @param resultType 具体类型
     * @return 定义的实体类型
     */
    @Override
    public <T> T sqlSelectOne(String sql, Class<T> resultType) {
        List<T> list = this.sqlSelectList(sql, resultType);
        return this.getOne(list);
    }

    /**
     * 查询单条数据返回实体类型
     *
     * @param sql        sql语句
     * @param value      参数
     * @param resultType 具体类型
     * @return 定义的实体类型
     */
    @Override
    public <T> T sqlSelectOne(String sql, Object value, Class<T> resultType) {
        List<T> list = this.sqlSelectList(sql, value, resultType);
        return this.getOne(list);
    }

    /**
     * 查询数据返回
     *
     * @param sql sql语句
     * @return List<Map < String, Object>>
     */
    @Override
    public List<Map<String, Object>> sqlSelectList(String sql) {
        String msId = this.msUtils.select(sql);
        return this.sqlSession.selectList(msId);
    }

    /**
     * 查询数据返回
     *
     * @param sql   sql语句
     * @param value 参数
     * @return List<Map < String, Object>>
     */
    @Override
    public List<Map<String, Object>> sqlSelectList(String sql, Object value) {
        Class<?> parameterType = value != null ? value.getClass() : null;
        String msId = this.msUtils.selectDynamic(sql, parameterType);
        return this.sqlSession.selectList(msId, value);
    }

    /**
     * 查询数据返回
     *
     * @param sql        sql语句
     * @param resultType 具体类型
     * @return List<T>
     */
    @Override
    public <T> List<T> sqlSelectList(String sql, Class<T> resultType) {
        String msId;
        if (resultType == null) {
            msId = this.msUtils.select(sql);
        } else {
            msId = this.msUtils.select(sql, resultType);
        }

        return this.sqlSession.selectList(msId);
    }

    /**
     * 查询数据返回
     *
     * @param sql        sql语句
     * @param value      参数
     * @param resultType 具体类型
     * @return List<T>
     */
    @Override
    public <T> List<T> sqlSelectList(String sql, Object value, Class<T> resultType) {
        Class<?> parameterType = value != null ? value.getClass() : null;
        String msId;
        if (resultType == null) {
            msId = this.msUtils.selectDynamic(sql, parameterType);
        } else {
            msId = this.msUtils.selectDynamic(sql, parameterType, resultType);
        }

        return this.sqlSession.selectList(msId, value);
    }

    /**
     * 插入数据
     *
     * @param sql sql语句
     * @return int
     */
    @Override
    public int sqlInsert(String sql) {
        String msId = this.msUtils.insert(sql);
        return this.sqlSession.insert(msId);
    }

    /**
     * 插入数据
     *
     * @param sql   sql语句
     * @param value 参数
     * @return int
     */
    @Override
    public int sqlInsert(String sql, Object value) {
        Class<?> parameterType = value != null ? value.getClass() : null;
        String msId = this.msUtils.insertDynamic(sql, parameterType);
        return this.sqlSession.insert(msId, value);
    }

    /**
     * 更新数据
     *
     * @param sql sql语句
     * @return int
     */
    @Override
    public int sqlUpdate(String sql) {
        String msId = this.msUtils.update(sql);
        return this.sqlSession.update(msId);
    }

    /**
     * 更新数据
     *
     * @param sql   sql语句
     * @param value 参数
     * @return int
     */
    @Override
    public int sqlUpdate(String sql, Object value) {
        Class<?> parameterType = value != null ? value.getClass() : null;
        String msId = this.msUtils.updateDynamic(sql, parameterType);
        return this.sqlSession.update(msId, value);
    }

    /**
     * 删除数据
     *
     * @param sql sql语句
     * @return int
     */
    @Override
    public int sqlDelete(String sql) {
        String msId = this.msUtils.delete(sql);
        return this.sqlSession.delete(msId);
    }

    /**
     * 查询数据返回List<T>
     *
     * @param sql   sql语句
     * @param value 参数
     * @return int
     */
    @Override
    public int sqlDelete(String sql, Object value) {
        Class<?> parameterType = value != null ? value.getClass() : null;
        String msId = this.msUtils.deleteDynamic(sql, parameterType);
        return this.sqlSession.delete(msId, value);
    }

    /**
     * 进行预编译
     */
    private class MSUtils {
        private Configuration configuration;
        private LanguageDriver languageDriver;

        private MSUtils(Configuration configuration) {
            this.configuration = configuration;
            this.languageDriver = configuration.getDefaultScriptingLanguageInstance();
        }

        private String newMsId(String sql, SqlCommandType sqlCommandType) {
            StringBuilder msIdBuilder = new StringBuilder(sqlCommandType.toString());
            msIdBuilder.append(".").append(sql.hashCode());
            return msIdBuilder.toString();
        }

        private boolean hasMappedStatement(String msId) {
            return this.configuration.hasStatement(msId, false);
        }

        private void newSelectMappedStatement(String msId, SqlSource sqlSource, final Class<?> resultType) {
            MappedStatement ms = (new MappedStatement.Builder(this.configuration, msId, sqlSource, SqlCommandType.SELECT)).resultMaps(new ArrayList<ResultMap>() {
                {
                    this.add((new org.apache.ibatis.mapping.ResultMap.Builder(com.culturalCenter.placeManage.mapper.SqlMapper.MSUtils.this.configuration, "defaultResultMap", resultType, new ArrayList(0))).build());
                }
            }).build();
            this.configuration.addMappedStatement(ms);
        }

        private void newUpdateMappedStatement(String msId, SqlSource sqlSource, SqlCommandType sqlCommandType) {
            MappedStatement ms = (new MappedStatement.Builder(this.configuration, msId, sqlSource, sqlCommandType)).resultMaps(new ArrayList<ResultMap>() {
                {
                    this.add((new org.apache.ibatis.mapping.ResultMap.Builder(com.culturalCenter.placeManage.mapper.SqlMapper.MSUtils.this.configuration, "defaultResultMap", Integer.TYPE, new ArrayList(0))).build());
                }
            }).build();
            this.configuration.addMappedStatement(ms);
        }

        private String select(String sql) {
            String msId = this.newMsId(sql, SqlCommandType.SELECT);
            if (this.hasMappedStatement(msId)) {
                return msId;
            } else {
                StaticSqlSource sqlSource = new StaticSqlSource(this.configuration, sql);
                this.newSelectMappedStatement(msId, sqlSource, Map.class);
                return msId;
            }
        }

        private String selectDynamic(String sql, Class<?> parameterType) {
            String msId = this.newMsId(sql + parameterType, SqlCommandType.SELECT);
            if (this.hasMappedStatement(msId)) {
                return msId;
            } else {
                SqlSource sqlSource = this.languageDriver.createSqlSource(this.configuration, sql, parameterType);
                this.newSelectMappedStatement(msId, sqlSource, Map.class);
                return msId;
            }
        }

        private String select(String sql, Class<?> resultType) {
            String msId = this.newMsId(resultType + sql, SqlCommandType.SELECT);
            if (this.hasMappedStatement(msId)) {
                return msId;
            } else {
                StaticSqlSource sqlSource = new StaticSqlSource(this.configuration, sql);
                this.newSelectMappedStatement(msId, sqlSource, resultType);
                return msId;
            }
        }

        private String selectDynamic(String sql, Class<?> parameterType, Class<?> resultType) {
            String msId = this.newMsId(resultType + sql + parameterType, SqlCommandType.SELECT);
            if (this.hasMappedStatement(msId)) {
                return msId;
            } else {
                SqlSource sqlSource = this.languageDriver.createSqlSource(this.configuration, sql, parameterType);
                this.newSelectMappedStatement(msId, sqlSource, resultType);
                return msId;
            }
        }

        private String insert(String sql) {
            String msId = this.newMsId(sql, SqlCommandType.INSERT);
            if (this.hasMappedStatement(msId)) {
                return msId;
            } else {
                StaticSqlSource sqlSource = new StaticSqlSource(this.configuration, sql);
                this.newUpdateMappedStatement(msId, sqlSource, SqlCommandType.INSERT);
                return msId;
            }
        }

        private String insertDynamic(String sql, Class<?> parameterType) {
            String msId = this.newMsId(sql + parameterType, SqlCommandType.INSERT);
            if (this.hasMappedStatement(msId)) {
                return msId;
            } else {
                SqlSource sqlSource = this.languageDriver.createSqlSource(this.configuration, sql, parameterType);
                this.newUpdateMappedStatement(msId, sqlSource, SqlCommandType.INSERT);
                return msId;
            }
        }

        private String update(String sql) {
            String msId = this.newMsId(sql, SqlCommandType.UPDATE);
            if (this.hasMappedStatement(msId)) {
                return msId;
            } else {
                StaticSqlSource sqlSource = new StaticSqlSource(this.configuration, sql);
                this.newUpdateMappedStatement(msId, sqlSource, SqlCommandType.UPDATE);
                return msId;
            }
        }

        private String updateDynamic(String sql, Class<?> parameterType) {
            String msId = this.newMsId(sql + parameterType, SqlCommandType.UPDATE);
            if (this.hasMappedStatement(msId)) {
                return msId;
            } else {
                SqlSource sqlSource = this.languageDriver.createSqlSource(this.configuration, sql, parameterType);
                this.newUpdateMappedStatement(msId, sqlSource, SqlCommandType.UPDATE);
                return msId;
            }
        }

        private String delete(String sql) {
            String msId = this.newMsId(sql, SqlCommandType.DELETE);
            if (this.hasMappedStatement(msId)) {
                return msId;
            } else {
                StaticSqlSource sqlSource = new StaticSqlSource(this.configuration, sql);
                this.newUpdateMappedStatement(msId, sqlSource, SqlCommandType.DELETE);
                return msId;
            }
        }

        private String deleteDynamic(String sql, Class<?> parameterType) {
            String msId = this.newMsId(sql + parameterType, SqlCommandType.DELETE);
            if (this.hasMappedStatement(msId)) {
                return msId;
            } else {
                SqlSource sqlSource = this.languageDriver.createSqlSource(this.configuration, sql, parameterType);
                this.newUpdateMappedStatement(msId, sqlSource, SqlCommandType.DELETE);
                return msId;
            }
        }
    }
}

然后做一个数据连接工厂类

SqlSessionFactoryConfig

代码100分/**
 * @author chaild
 * @Date 2020年6月23日18:25:22
 *  创建SQL连接工厂类
 * */
@Configuration
public class SqlSessionFactoryConfig {
    @javax.annotation.Resource
    DruidDataSource dataSource;

    @Bean
    @Primary
    public SqlSessionFactory sqlSessionFactory() throws Exception {
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(dataSource);//更多参数请自行注入
        bean.setPlugins(new Interceptor[]{new SqlInterceptor()});
        Resource[] resources = new PathMatchingResourcePatternResolver()
                .getResources("classpath*:mapper/*.xml");
        bean.setMapperLocations(resources);
        return bean.getObject();
    }
}

使用示例：

@Autowired 
private SqlMapper sqlMapper;

###selectList

//查询，返回List<Map>
List<Map<String, Object>> list = sqlMapper.selectList("select * from country where id < 11");

//查询，返回指定的实体类
List<Country> countryList = sqlMapper.selectList("select * from country where id < 11", Country.class);

//查询，带参数
countryList = sqlMapper.selectList("select * from country where id < #{id}", 11, Country.class);

//复杂点的查询，这里参数和上面不同的地方，在于传入了一个对象
Country country = new Country();
country.setId(11);
countryList = sqlMapper.selectList("<script>" +
        "select * from country " +
        "   <where>" +
        "       <if test="id != null">" +
        "           id &lt; #{id}" +
        "       </if>" +
        "   </where>" +
        "</script>", country, Country.class);
##复杂查询使用map传入参数   
 Map<String,String> map=new HashMap<>();
map.put("id","21321312312312312");
map.put("status","1");
sqlMapper.sqlSelectList("select * from tb_admin where id=#{id} and status=#{status}",map,Admin.class);


###selectOne 查询单条数据

Map<String, Object> map = sqlMapper.selectOne("select * from country where id = 35");

map = sqlMapper.selectOne("select * from country where id = #{id}", 35);

Country country = sqlMapper.selectOne("select * from country where id = 35", Country.class);

country = sqlMapper.selectOne("select * from country where id = #{id}", 35, Country.class);
###insert,update,delete

###insert 插入数据
int result = sqlMapper.insert("insert into country values(1921,‘天朝‘,‘TC‘)");

Country tc = new Country();
tc.setId(1921);
tc.setCountryname("天朝");
tc.setCountrycode("TC");
//注意这里的countrycode和countryname故意写反的
result = sqlMapper.insert("insert into country values(#{id},#{countrycode},#{countryname})"
                          , tc);


###update 更新使用
result = sqlMapper.update("update country set countryname = ‘天朝‘ where id = 35");

tc = new Country();
tc.setId(35);
tc.setCountryname("天朝");

int result = sqlMapper.update("update country set countryname = #{countryname}" +
           " where id in(select id from country where countryname like ‘A%‘)", tc);


##delete 删除使用
result = sqlMapper.delete("delete from country where id = 35");
result = sqlMapper.delete("delete from country where id = #{id}", 35);