MyBatis拦截器：给参数对象属性赋值

在mybatis的mapper.xml文件中,我们可以使用#{}或${}的方式获取到参数,这些参数都需要提前我们在mapper.java接口文件中通过参数的方式传入参数才能取到

为了扩展参数,我们需要了解mybatis是怎么帮我们保管mapper.java中传入的参数的

进入Executor.java接口查看query方法,可以看到第一个参数MappedStatement对象中有一个parameterMap字段,该字段是Map类型保存我们的参数,那我们只需要在拦截器中对MappedStatement对象的parameterMap中put自己想要的参数即可

@Intercepts({
        @Signature(type = Executor.class, method = "query", args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class}),
        @Signature(type = Executor.class, method = "query", args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class, CacheKey.class, BoundSql.class})
})
public class DeptDataScopeInterceptor implements Interceptor {

    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        Object[] args = invocation.getArgs();

        if (ArrayUtils.isNotEmpty(args)) {
            MappedStatement mappedStatement = (MappedStatement) args[0];
            DataScope dataScope = getDataScope(mappedStatement);

            StringBuilder sqlString = new StringBuilder();
            if (dataScope != null) {
                Long companyOrgId = SecurityUtils.getCompanyOrgId();

                if (companyOrgId != null) {
                    sqlString.append(StringUtils.format(" {}.{} = {} ", dataScope.orgAlias(), dataScope.orgColumnName(), companyOrgId));
                } else {
                    sqlString.append(" 1=0 ");
                }
            }

            if (args[1] == null) {
                args[1] = new MapperMethod.ParamMap<>();
            }
            Map map = (Map) args[1];
            // 此处为重点
            map.put("dataScope", sqlString.length() > 0 ? " (" + sqlString.toString() + ")" : "");
        }
        return invocation.proceed();
    }

    private DataScope getDataScope(MappedStatement mappedStatement) {
        String id = mappedStatement.getId();
        // 获取 Class Method
        String clazzName = id.substring(0, id.lastIndexOf('.'));
        String mapperMethod = id.substring(id.lastIndexOf('.') + 1);

        Class<?> clazz;
        try {
            clazz = Class.forName(clazzName);
        } catch (ClassNotFoundException e) {
            return null;
        }
        Method[] methods = clazz.getMethods();

        DataScope dataScope = null;
        for (Method method : methods) {
            if (method.getName().equals(mapperMethod)) {
                dataScope = method.getAnnotation(DataScope.class);
                break;
            }
        }
        return dataScope;
    }

    @Override
    public Object plugin(Object target) {
        return Plugin.wrap(target, this);
    }

    @Override
    public void setProperties(Properties properties) {

    }
}

在map中加入dataScope后,即可在相应的mapper.xml中使用#{dataScope}或${dataScope}或取到该参数

如果项目中使用了pageHelper插件,则启动项目后,执行到对应的mapper查询的时候,如果mapper.xml中使用了上述方式添加的参数,那么项目会报错,因为pageHelper的拦截器会在我们的拦截器之前执行,pageHelper的拦截器中对参数进行了校验,因为自定的拦截器还没有执行,则Map中不会有自定义参数,当pageHelper的拦截器开始校验参数的时候就会报错找不到参数

如何将自定义的拦截器放在PageHelper拦截器前方执行
查阅资料后发现SqlSessionFactory中加入的拦截器,先加入的会后执行,后加入的先执行,那么我们需要让自定义的拦截器在PageHelper后加入,查看PageHelper的自动配置类

@Configuration
@ConditionalOnBean(SqlSessionFactory.class)
@EnableConfigurationProperties(PageHelperProperties.class)
@AutoConfigureAfter(MybatisAutoConfiguration.class)
@Lazy(false)
public class PageHelperAutoConfiguration {

    @Autowired
    private List<SqlSessionFactory> sqlSessionFactoryList;

    @Autowired
    private PageHelperProperties properties;

    /**
     * 接受分页插件额外的属性
     *
     * @return
     */
    @Bean
    @ConfigurationProperties(prefix = PageHelperProperties.PAGEHELPER_PREFIX)
    public Properties pageHelperProperties() {
        return new Properties();
    }

    @PostConstruct
    public void addPageInterceptor() {
        PageInterceptor interceptor = new PageInterceptor();
        Properties properties = new Properties();
        //先把一般方式配置的属性放进去
        properties.putAll(pageHelperProperties());
        //在把特殊配置放进去，由于close-conn 利用上面方式时，属性名就是 close-conn 而不是 closeConn，所以需要额外的一步
        properties.putAll(this.properties.getProperties());
        interceptor.setProperties(properties);
        for (SqlSessionFactory sqlSessionFactory : sqlSessionFactoryList) {
            org.apache.ibatis.session.Configuration configuration = sqlSessionFactory.getConfiguration();
            if (!containsInterceptor(configuration, interceptor)) {
                configuration.addInterceptor(interceptor);
            }
        }
    }

    /**
     * 是否已经存在相同的拦截器
     *
     * @param configuration
     * @param interceptor
     * @return
     */
    private boolean containsInterceptor(org.apache.ibatis.session.Configuration configuration, Interceptor interceptor) {
        try {
            // getInterceptors since 3.2.2
            return configuration.getInterceptors().contains(interceptor);
        } catch (Exception e) {
            return false;
        }
    }

}

pageHelper的拦截器会在Mybatis的自动配置后在做相应配置,那么我们可以写一个配置类,让他在PageHelper的配置类后再执行

@Configuration
@ConditionalOnBean(SqlSessionFactory.class)
@EnableConfigurationProperties(PageHelperProperties.class)
@Lazy(false)
@AutoConfigureAfter(PageHelperAutoConfiguration.class)
public class DeptDataScopeInterceptorConfig {

    @Autowired
    private List<SqlSessionFactory> sqlSessionFactoryList;

    @PostConstruct
    public void addPageInterceptor() {
        DeptDataScopeInterceptor interceptor = new DeptDataScopeInterceptor();
        for (SqlSessionFactory sqlSessionFactory : sqlSessionFactoryList) {
            sqlSessionFactory.getConfiguration().addInterceptor(interceptor);
        }
    }

}

此处需要注意的是,如果DeptDataScopeInterceptorConfig配置类会被SpringBoot项目自动扫描到,尽管配置的顺序是在PageHelper自动配置后再配置,但是被SpringBoot扫描到的配置类会优先加载,所以要防止SpringBoot扫描带该配置,有如下几种方案

如果该配置类已经会被扫描到,则可以使用排出的方式排除掉该类,然后用spring.factories的方式做自动配置，可以使用

1.@SpringBootApplication(exclude = DeptDataScopeInterceptorConfig.class)

2.@ComponentScan(excludeFilters = @ComponentScan.Filter(type = FilterType.ASSIGNABLE_TYPE, value = DeptDataScopeInterceptorConfig.class))

3.添加到spring.factories中文件路径地址resrouces/META-INF/spring.factories(如果报错，可以试试在加上@EnableAutoConfiguration(exclude = DeptDataScopeInterceptorConfig.class))

org.springframework.boot.autoconfigure.EnableAutoConfiguration=
  top.sclf.common.datascope.config.DeptDataScopeInterceptorConfig

参考

https://blog.csdn.net/qq1010830256/article/details/115617442

http://xtong.tech/2018/08/01/MyBatis%E6%8B%A6%E6%88%AA%E5%99%A8%E5%9B%A0pagehelper%E8%80%8C%E5%A4%B1%E6%95%88%E7%9A%84%E9%97%AE%E9%A2%98%E8%A7%A3%E5%86%B3/