使用GeoTools关联CSV属性到Shapefile失败，求解决方案

需将导入的CSV文件属性传递至已存入FeatureCollection的Shapefile，通过Shapefile的SCH_SG属性与CSV的SCH_GEM属性匹配特征并更新属性，但多次尝试后属性仍未成功添加。

关联方法 #

public SimpleFeatureCollection linkCsvShp(SimpleFeatureCollection sfColl) {
    // 遍历Shapefile数据源的要素并更新属性
    try (SimpleFeatureIterator it = sfColl.features()) {
        DefaultFeatureCollection newSfc = new DefaultFeatureCollection();
        while (it.hasNext()) {
            SimpleFeature sf = it.next();
            String shpKeyAttribute = (String) sf.getAttribute("SCH_SG");
            try (FeatureIterator<SimpleFeature> csvFeatures = csvCollection.features()) {
                while (csvFeatures.hasNext()) {
                    SimpleFeature csvFeature = csvFeatures.next();
                    Object csvAttribute = csvFeature.getAttribute("SCH_GEM");
                    if (csvAttribute != null && csvAttribute.equals(shpKeyAttribute)) {
                        // 更新Shape要素的属性
                        sf.setAttribute("GEM_TYP", csvFeature.getAttribute("GEM_TYP"));
                        sf.setAttribute("KREIS", csvFeature.getAttribute("KREIS"));
                        sf.setAttribute("REGION", csvFeature.getAttribute("REGION"));
                        sf.setAttribute("EINW_KL", csvFeature.getAttribute("EINW_KLASSE"));
                        newSfc.add(sf);
                        break;
                    }
                }
            }
        }
        it.close();
        setStatus("Das Punktfeature wurde erfolgreich erweitert!");
    }

    return sfColl;
}

Shapefile加载方法 #

java.net.URL shapeURL = pointFile.toURI().toURL();
store = new ShapefileDataStore(shapeURL);
store.setTryCPGFile(true);
SimpleFeatureSource fSource = store.getFeatureSource();
SimpleFeatureCollection sfColl = linkCsvShp(fSource.getFeatures());

CSV加载方法 #

private FeatureCollection<SimpleFeatureType, SimpleFeature> csvCollection;
public void loadCsv(String path) {
    Map<String, Serializable> params = new HashMap<String, Serializable>();
    params.put("file", path);

    DataStore store;
    try {
        store = DataStoreFinder.getDataStore(params);
        String typeName = store.getTypeNames()[0];
        FeatureSource<SimpleFeatureType, SimpleFeature> source = store.getFeatureSource(typeName);
        Filter filter = Filter.INCLUDE;

        csvCollection = source.getFeatures(filter);
    } catch (IOException e) {
        e.printStackTrace();
    }
}

问题排查与解决方案 #

1. 返回值错误 #

当前linkCsvShp方法最后返回原始的sfColl，而非处理后的newSfc，导致所有修改无法生效。修改返回语句：

return newSfc;

2. 要素类型不兼容 #

Shapefile的SimpleFeatureType必须包含要添加的属性（GEM_TYP、KREIS、REGION、EINW_KL），否则setAttribute调用会失败。需先扩展要素类型：

// 扩展原始SimpleFeatureType
SimpleFeatureType originalType = sfColl.getSchema();
SimpleFeatureTypeBuilder builder = new SimpleFeatureTypeBuilder();
builder.init(originalType);
// 按CSV属性类型添加新字段
builder.add("GEM_TYP", String.class);
builder.add("KREIS", String.class);
builder.add("REGION", String.class);
builder.add("EINW_KL", String.class);
SimpleFeatureType newType = builder.buildFeatureType();

// 转换要素类型后再赋值
SimpleFeature newFeature = DataUtilities.retype(newType, sf);
newFeature.setAttribute("GEM_TYP", csvFeature.getAttribute("GEM_TYP"));
newFeature.setAttribute("KREIS", csvFeature.getAttribute("KREIS"));
newFeature.setAttribute("REGION", csvFeature.getAttribute("REGION"));
newFeature.setAttribute("EINW_KL", csvFeature.getAttribute("EINW_KLASSE"));
newSfc.add(newFeature);

3. 字符串匹配失效 #

检查SCH_SG与SCH_GEM是否存在空格、大小写差异或数据类型不匹配（如一个是数字字符串，一个是整数）。添加标准化处理：

String shpKeyAttribute = (String) sf.getAttribute("SCH_SG");
if (shpKeyAttribute != null) {
    shpKeyAttribute = shpKeyAttribute.trim();
}

String csvAttribute = csvFeature.getAttribute("SCH_GEM") != null ? 
    csvFeature.getAttribute("SCH_GEM").toString().trim() : null;

if (csvAttribute != null && csvAttribute.equals(shpKeyAttribute)) {
    // 执行属性更新逻辑
}

4. 资源冗余关闭 #

try-with-resources会自动关闭迭代器，可移除多余的it.close()语句，避免潜在异常。

5. 未匹配要素保留 #

若需要保留未匹配的Shapefile要素，在CSV循环结束后添加：

if (!newSfc.contains(sf)) {
    newSfc.add(sf);
}

内容的提问来源于stack exchange，提问作者Marc