背景
目前有一个区的图斑数据需要分乡镇展示，所以采用FeatureLayer 的 definitionExpression 构造SQL语句进行过滤，官方提供的示例：
1 // Set definition expression in constructor to only display trees with scientific name Ulmus pumila
2 const layer = new FeatureLayer({
3 url: "https://services.arcgis.com/V6ZHFr6zdgNZuVG0/arcgis/rest/services/Landscape_Trees/FeatureServer/0",
4 definitionExpression: "Sci_Name = 'Ulmus pumila'"
5 });
// Set the definition expression directly on layer instance to only display trees taller than 50ft layer.definitionExpression = "HEIGHT > 50";
这个问题出来后，直接让我懵逼了，总不能把十几个乡镇的图斑分别发布出来然后加载吧，这样子太麻烦了，当然这是最坏的打算。
“领导”的意思是让后端来封装一层，这个在其他纯前端项目还好，sql语句放到后端，返回个json就好了。但这毕竟是GIS项目，人家都封装好了，就需要个url，塞个json不合适吧....还说arcgis server发布的就只能做demo，搞得我有点怀疑人生了
环境
Vue3.0
@arcgis/core
问题
利用definitionExpression 虽然方便，但是处于安全考虑，在正式环境下会被拦截。现场给的回复是“URL(0141)::where=town%20%3D%20%27320509101000%27%20and%20xcdcqk%20%3C%3E%20%270%27”，被认定为sql注入攻击 拦截了
解决方案
其实这个只需要前端规避下在请求url里面不要携带‘where’即可，所以就不要想着直接在定义featurelayer时过滤了，这样子肯定还是会携带‘where’，所以考虑在featurelayer加载后再处理。
我的解决方案是利用layerview的filter来做筛选:
1 // display rain gauges where their water percent is over 30%
2 // and if the gauges are completely contained by the 10-mile
3 // buffer around the filter geometry
4 featureLayerView.filter = new FeatureFilter({
5 where: "percentile >= 30",
6 geometry: filterPolygon,
7 spatialRelationship: "contains",
8 distance: 10,
9 units: "miles"
10 });
对比
项目原代码：
1 let definitionExpression
2 if (townCode) {
3 definitionExpression = `town = '${townCode}' and xcdcqk <> '0'`
4 } else {
5 definitionExpression = "xcdcqk <> '0'"
6 }
7 const pathchRender = {
8 type: 'unique-value',
9 field: 'needCheck',
10 defaultSymbol: {
11 type: 'simple-fill', // autocasts as new SimpleFillSymbol()
12 color: [227, 139, 79, 0],
13 outline: {
14 // autocasts as new SimpleLineSymbol()
15
16 color: [0, 245, 255],
17 width: 2.5
18 }
19 },
20 uniqueValueInfos: [
21 {
22 // All features with value of "East" will be green
23 value: 1,
24 symbol: {
25 type: 'simple-fill', // autocasts as new SimpleFillSymbol()
26 color: [227, 139, 79, 0],
27 outline: {
28 // autocasts as new SimpleLineSymbol()
29 color: [0, 245, 255],
30 width: 2.5
31 }
32 }
33 },
34 {
35 // All features with value of "East" will be green
36 value: 0,
37 symbol: {
38 type: 'simple-fill', // autocasts as new SimpleFillSymbol()
39 color: [227, 139, 79, 0],
40 outline: {
41 // autocasts as new SimpleLineSymbol()
42
43 color: [150, 150, 150],
44 width: 2.5
45 }
46 }
47 }
48 ]
49 }
50
51 const patchesLayer = new FeatureLayer({
52 id: 'patchesLayer',
53 title: '图斑',
54 url: patchesLayerUrl,
55 definitionExpression: definitionExpression,
56 outFields: [
57 'objectid_1',
58 'fwbh',
59 'lon',
60 'lat',
61 'needCheck',
62 'fwlb',
63 'fwmj',
64 'flloors',
65 'height'
66 ],
67 objectIdField: 'objectid_1',
68 editingEnabled: true,
69 renderer: pathchRender
70 })
71 map.layers.add(patchesLayer)
View Code
请求效果图，能看到查询的url里面携带‘where’：
改良后的项目代码：
1 let definitionExpression
2 if (townCode) {
3 definitionExpression = `town = '${townCode}' and xcdcqk <> '0'`
4 } else {
5 definitionExpression = "xcdcqk <> '0'"
6 }
7 const pathchRender = {
8 type: 'unique-value',
9 field: 'needCheck',
10 defaultSymbol: {
11 type: 'simple-fill', // autocasts as new SimpleFillSymbol()
12 color: [227, 139, 79, 0],
13 outline: {
14 // autocasts as new SimpleLineSymbol()
15
16 color: [0, 245, 255],
17 width: 2.5
18 }
19 },
20 uniqueValueInfos: [
21 {
22 // All features with value of "East" will be green
23 value: 1,
24 symbol: {
25 type: 'simple-fill', // autocasts as new SimpleFillSymbol()
26 color: [227, 139, 79, 0],
27 outline: {
28 // autocasts as new SimpleLineSymbol()
29 color: [0, 245, 255],
30 width: 2.5
31 }
32 }
33 },
34 {
35 // All features with value of "East" will be green
36 value: 0,
37 symbol: {
38 type: 'simple-fill', // autocasts as new SimpleFillSymbol()
39 color: [227, 139, 79, 0],
40 outline: {
41 // autocasts as new SimpleLineSymbol()
42
43 color: [150, 150, 150],
44 width: 2.5
45 }
46 }
47 }
48 ]
49 }
50
51 const patchesLayer = new FeatureLayer({
52 id: 'patchesLayer',
53 title: '图斑',
54 url: patchesLayerUrl,
55 // definitionExpression: definitionExpression,
56 outFields: [
57 'objectid_1',
58 'fwbh',
59 'lon',
60 'lat',
61 'needCheck',
62 'fwlb',
63 'fwmj',
64 'flloors',
65 'height'
66 ],
67 objectIdField: 'objectid_1',
68 editingEnabled: true,
69 renderer: pathchRender
70 })
71 map.layers.add(patchesLayer)
72 view.whenLayerView(patchesLayer).then((layerView) => {
73 patchLayerView = layerView
74 patchLayerView.filter = {
75 where: definitionExpression
76 }
77 })
View Code
请求效果图,可以看到请求的url中已经不再携带‘where’：
标签：autocasts,color,definitionExpression,JavaScript,FeatureLayer,value,new,where From： https://www.cnblogs.com/youzi-xuchongyou/p/16615838.html