【解决办法】文档地址参考https://help.supermap.com/iServer/mergedProjects/iServerJavadoc/com/supermap/services/components/spi/ogc/WMS.html?rhhlterm=GetLegendGraphic&rhsearch=GetLegendGraphic，一个获取图例的示例链接为http://localhost:8090/iserver/services/map-WorkSpace/wms111/testMap?SERVICE=WMS&REQUEST=GetLegendGraphic&FORMAT=image/png
