Java【付诸实践 01】使用org.apache.ibatis.plugin.Interceptor拦截器实现全局mapper.xml参数注入（可用于切换数据

@Intercepts({
        @Signature(method = "update",
                args = {MappedStatement.class, Object.class}, type = Executor.class),
        @Signature(method = "query",
                args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class}, type = Executor.class)
})
public class SchemaInterceptor implements Interceptor {
    /**
     * 这里没有打印日志
     */
    private static Log LOG = LogFactory.getLog(SchemaInterceptor.class);

    /**
     * mapper.xml 使用SCHEMA时的参数名称
     */
    private static final String SCHEMA = "schemaName";

    /**
     * 设置默认的schema
     */
    private String schema = "public";

    /**
     * 拦截到的动态SQL处理后放入此对象
     */
    private Set<Integer> sourceStorage = new HashSet<>();

    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        Object[] args = invocation.getArgs();
        MappedStatement mappedStatement = (MappedStatement) args[0];
        SqlSource sqlSource = mappedStatement.getSqlSource();
        // 只拦截动态SQL
        if (sqlSource instanceof DynamicSqlSource) {
            // 获取到sqlNode对象
            Field field = DynamicSqlSource.class.getDeclaredField("rootSqlNode");
            field.setAccessible(true);
            SqlNode sqlNode = (SqlNode) field.get(sqlSource);
            if (!sourceStorage.contains(sqlSource.hashCode())) {
                // 获取动态代理对象
                Map<String, Object> argMap = (HashMap<String, Object>) args[1];
                // 判断是否传递 schemaName或schema 如果已经传递则使用用户传递的值 否则使用默认值
                String schemaNameStr = "schemaName", schemaStr = "schema";
                if (StringUtils.isEmpty(MapUtils.getString(argMap, schemaNameStr)) && StringUtils.isEmpty(MapUtils.getString(argMap, schemaStr))) {
                    SqlNode proxyNode = proxyNode(sqlNode);
                    field.set(sqlSource, proxyNode);
                }
                sourceStorage.add(sqlSource.hashCode());
            }
        }
        return invocation.proceed();
    }

    /**
     * 通过动态代理对象 添加schema参数
     *
     * @param sqlNode SQL节点
     * @return SqlNode
     */
    private SqlNode proxyNode(SqlNode sqlNode) {
        return (SqlNode) Proxy.newProxyInstance(sqlNode.getClass().getClassLoader(),
                new Class[]{SqlNode.class}, new SqlNodeInvocationHandler(sqlNode));
    }

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

    @Override
    public void setProperties(Properties properties) {
        LOG.debug("setProperties====>" + properties);
    }

    private class SqlNodeInvocationHandler implements InvocationHandler {
        private SqlNode target;

        SqlNodeInvocationHandler(SqlNode target) {
            super();
            this.target = target;
        }

        @Override
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
            DynamicContext context = (DynamicContext) args[0];
            // 给schema添加.
            setSchema(schema);
            // 设置schema
            context.getBindings().put(SCHEMA, schema);
            return method.invoke(target, args);
        }

    }

    /**
     * 给schema 添加.
     *
     * @param schema schemaName
     */
    private void setSchema(String schema) {
        String pointStr = ".";
        if (StringUtils.isNotBlank(schema)) {
            if (!schema.endsWith(pointStr)) {
                schema += pointStr;
            }
        }
        this.schema = schema;
    }
}

    @Bean(name = "sqlSessionFactory_greenplum")
    @Primary
    public SqlSessionFactory sqlSessionFactory(@Qualifier("dataSource_greenplum") DataSource dataSource)
            throws Exception {
        final SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
        // 设置数据源参数
        sessionFactory.setDataSource(dataSource);
        // mapper路径和mybatis配置文件路径
        sessionFactory.setMapperLocations(new PathMatchingResourcePatternResolver()
                .getResources(GreenplumConfiguration.MAPPER_LOCATION));
        sessionFactory.setConfigLocation(new ClassPathResource(mybatisConfigPath));
        // 添加自定义的schema拦截器【此次配置的重点】
        sessionFactory.setPlugins(new Interceptor[]{new SchemaInterceptor()});
        return sessionFactory.getObject();
    }

<!--执行插入文件数据SQL-->
<insert id="insertFileData" parameterType="map">
	insert into ${schemaName}${target_table}( ${table_field} ) VALUES ( ${field_value} )
</insert>