72 lines
2.8 KiB
Markdown
72 lines
2.8 KiB
Markdown
---
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title: GeoTools 要素查询
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date: 2023-12-22
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author: ac
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categories:
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- GIS
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tags:
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- GeoTools
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---
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## GeoTools 要素查询
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### 1.简介
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本文介绍用于查询`DataStores`数据存储(如`shapefiles`、数据库和`Web Feature Servers`)的`Filter API`。
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个人观点：Java关于`JDBC`的一些概念，与`GeoTools`中的类的对应关系如下：
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| GeoTools | JDBC | |
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|:--------------------- |:------------------- | ----------- |
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| `FeatureStore` | `Connection` | 数据库连接 |
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| `FeatureSource` | `PreparedStatement` | `Table` |
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| `FeatureCollection` | `ResultSet` | 结果集 |
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| `AttributeDescriptor` | `ResultSetMetaData` | 结果集元数据（属性列） |
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| `FeatureIterator` | | |
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示例：
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```java
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String shpPath = "D:\\demo\\tutorial\\data\\china\\330000.shp";
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File shpFile = new File(shpPath);
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ShapefileDataStore shapefileDataStore = new ShapefileDataStore(shpFile.toURI().toURL());
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// 设置编码,防止属性的中文字符出现乱码
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shapefileDataStore.setCharset(Charset.forName("UTF-8"));
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// 获取文件名
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String typeName = shapefileDataStore.getTypeNames()[0];
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// 通过文件名在数据存储中找到对应的featuresource（table）
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FeatureSource featuresource = shapefileDataStore.getFeatureSource(typeName);
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// 属性查询
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// Filter filter = CQL.toFilter("adcode = 330100");
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// Filter filter = CQL.toFilter("name like '%州市%' and childrenNu >8");
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// 空间查询
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// CQL.toCQL()
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Filter filter = CQL.toFilter("BBOX(the_geom, 118.77, 119.626, 28.908, 29.653)");
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SimpleFeatureCollection features = (SimpleFeatureCollection)featuresource.getFeatures(filter);
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int count = features.size();
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System.out.println("查询结果数量："+count);
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// 获取当前矢量数据有哪些属性字段值
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List<AttributeDescriptor> attributes = features.getSchema().getAttributeDescriptors();
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// 拿到迭代器
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SimpleFeatureIterator simpleFeatureIterator = features.features();
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// 遍历每一个要素
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while(simpleFeatureIterator.hasNext()) {
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SimpleFeature simpleFeature = simpleFeatureIterator.next();
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System.out.println("-----------分割线-------------");
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// java8新特性流api
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attributes.stream().forEach((a) -> {
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// 依次读取这个shape中每一个属性值，当然这个属性值，可以处理其它业务
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System.out.println(a.getLocalName() + ":" + simpleFeature.getAttribute(a.getLocalName()));
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});
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}
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```
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从上述可以看到，不管是什么类型的数据源，访问的顺序是先通过`FeatureStore`连接数据源，然后从`store`中获取`FeatureSource`（类似于表），最后通过`cql`类来构建查询条件传入`FeatureSource`的`getFeatures`方法中，可以得到满足条件的要素集`FeatureCollection`。
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