52°North-WPS-学习-客户端API教程

https://wiki.52north.org/Geoprocessing/ClientAPI
https://wiki.52north.org/Geoprocessing/TutorialClientAPI

1. 获取SDK (maven)

在maven的配置文件的相关profile中，或者项目的pom文件中添加组件仓库

<repository>
   <id>n52-releases</id>
   <name>52n Releases</name>
   <url>http://52north.org/maven/repo/releases</url>
   <releases>
      <enabled>true</enabled>
   </releases>
   <snapshots>
      <enabled>true</enabled>
   </snapshots>
</repository>

添加项目依赖

<dependency>
    <groupId>org.n52.wps</groupId>
    <artifactId>52n-wps-client-lib</artifactId>
    <version>3.6.1</version>
</dependency>

从github获取wps_config.xml文件（如果直接使用的war包，一般在config目录下已经存在），将其放置到 classpath 目录（maven项目的 resources下面），或者在第一次调用代码时使用它：

WPSConfig.getInstance("path to your wps_config.xml");

2. GetCapabilities

此部分说明如何请求 WPS Capabilities文档并处理响应。示例：

public CapabilitiesDocument requestGetCapabilities(String url) throws WPSClientException {
        WPSClientSession wpsClient = WPSClientSession.getInstance(); // 初始化WPSClient session
        boolean connected = wpsClient.connect(url);//注册WPS URL
        CapabilitiesDocument capabilities = wpsClient.getWPSCaps(url);// 发生capabilities 请求
        ProcessBriefType[] processList = capabilities.getCapabilities()             .getProcessOfferings().getProcessArray();
        for (ProcessBriefType process : processList) {
            System.out.println(process.getIdentifier().getStringValue());
        }
        return capabilities;
    }

请求获得的Capabilities Document 结构与WPS规范中的一样。要获取详细信息，例如处理列表（ list of processes），需要通过ProcessOfferings ：

capabilities.getCapabilities().getProcessOfferings().getProcessArray();

每个处理都是遵循WPS规范的ProcessBriefType 类型。获取处理过程实例标识符的方法：

process.getIdentifier().getStringValue());

3. DescribeProcess

此部分说明如何请求 WPS DescribeProcess 文档并处理响应。示例：

public ProcessDescriptionType requestDescribeProcess(String url, String processID) throws IOException {
        WPSClientSession wpsClient = WPSClientSession.getInstance();
       // 获取处理方法描述，processID 是上面获得的实例标识符，即 ows:Identifier 的值
        ProcessDescriptionType processDescription = wpsClient.getProcessDescription(url, processID); 
44System.out.println("Process description:\n" + processDescription.xmlText() + "\n");
        // 获取处理过程的所有的输入数据描述
  		InputDescriptionType[] inputList = processDescription.getDataInputs().getInputArray(); 
        for (InputDescriptionType input : inputList) {
            System.out.println(input.getIdentifier().getStringValue());
        }
        return processDescription;
    }

4. Execute

此部分说明如何执行 WPS 处理并处理响应。示例：

// create the request, add literal input
public IData executeProcess(String url, String processID, ProcessDescriptionType processDescription, HashMap<String, Object> inputs) throws Exception {
        ExecuteRequestBuilder executeBuilder = new ExecuteRequestBuilder(processDescription);
        for (InputDescriptionType input : processDescription.getDataInputs().getInputArray()) {
            String inputName = input.getIdentifier().getStringValue();
            Object inputValue = inputs.get(inputName);
            if (input.getLiteralData() != null) {
                if (inputValue instanceof String) {
                    executeBuilder.addLiteralData(inputName,(String) inputValue);
                }
            } else if (input.getComplexData() != null) {
                // Complexdata by value
                if (inputValue instanceof FeatureCollection) {
                    IData data = new GTVectorDataBinding((FeatureCollection) inputValue);
                    executeBuilder.addComplexData(inputName,data,
                                    "http://schemas.opengis.net/gml/3.1.1/base/feature.xsd",
                                    null, "text/xml");
                }
                // Complexdata Reference
                if (inputValue instanceof String) {
                    executeBuilder.addComplexDataReference(inputName, (String) inputValue,
                                    "http://schemas.opengis.net/gml/3.1.1/base/feature.xsd",
                                    null, "text/xml");
                }
                if (inputValue == null && input.getMinOccurs().intValue() > 0) {
                    throw new IOException("Property not set, but mandatory: "+ inputName);
                }
            }
        }
        executeBuilder.setMimeTypeForOutput("text/xml", "result");
        executeBuilder.setSchemaForOutput(
                "http://schemas.opengis.net/gml/3.1.1/base/feature.xsd","result");
        // build and send the request document
  		ExecuteDocument execute = executeBuilder.getExecute();
        execute.getExecute().setService("WPS");
        WPSClientSession wpsClient = WPSClientSession.getInstance();
        Object response = wpsClient.execute(url, execute);
 		
        if (response instanceof ExecuteResponseDocument) {
            ExecuteResponseDocument responseDoc = (ExecuteResponseDocument) responseObject;
            ExecuteResponseAnalyser analyser = new ExecuteResponseAnalyser(
                    execute, responseDoc, processDescription);
            IData data = (IData) analyser.getComplexDataByIndex(0,GTVectorDataBinding.class);
            return data;
        }
        throw new Exception("Exception: " + response.toString());
    }

首先需要初始化一个 ExecuteRequestBuilder 对象，用于构建一个真正的WPS Execute请求。其需要的 ProcessDescriptionType 对象可通过第3部分的DescribeProcess 获取。

然后，需要设置输入数据，有3种方式：

Literaldata input

字符型数据，如数字、字符串等。

executeBuilder.addLiteralData(inputName, (String)inputValue);

输入数据的标识符（inputName）可通过ProcessDescription获取。

Complexdata input by value

复合型数据，如GML Features，使用

IData data = new GTVectorDataBinding((FeatureCollection) inputValue);
executeBuilder.addComplexData(inputName, data, "http://schemas.opengis.net/gml/3.1.1/base/feature.xsd", null,"text/xml");

需要一个输入数据标识符和一个IData类型的实际数据。IData 是一个接口，常用的实现类有：

Geotools 中用于矢量数据的 GTVectorDataBinding
用于任意文件数据的 GenericFileDataBinding . 同样需要数据模式（ schema）, 编码（encoding）和输入数据类型的 mimetype. 支持的数据格式可通过 ProcessDescription查看。

Complexdata input by reference

复合型数据，如只通过URL获取的 GML Features，使用

executeBuilder.addComplexDataReference(inputName, (String) inputValue, "http://schemas.opengis.net/gml/3.1.1/base/feature.xsd", null,"text/xml");

需要输入数据标识符以及一个指向地理数据资源的URL的字符串，如 WFS Getlayers 请求（URL）. 此外还需要In schema, encoding 和mimetype.

当设置完所有输入数据之后，必须设置输出数据的格式，包括mimetype和可选的schema（用于矢量数据），例如

executeBuilder.setMimeTypeForOutput("text/xml", "result");
executeBuilder.setSchemaForOutput("http://schemas.opengis.net/gml/3.1.1/base/feature.xsd", "result");

此方法为标识符为“result”的输出数据设置了schema。支持的schema列表可在ProcessDescription 中查询得到。

Note: 编码（encoding）只有在与默认的编码不一致时才需要设置。如果需要参数二进制数据值，可以设置编码为 “base64“ 。

完整示例代码

import net.opengis.wps.x100.CapabilitiesDocument;
import net.opengis.wps.x100.ExecuteDocument;
import net.opengis.wps.x100.ExecuteResponseDocument;
import net.opengis.wps.x100.InputDescriptionType;
import net.opengis.wps.x100.ProcessBriefType;
import net.opengis.wps.x100.ProcessDescriptionType;
import org.geotools.feature.FeatureCollection;
import org.n52.wps.client.ExecuteResponseAnalyser;
import org.n52.wps.client.WPSClientException;
import org.n52.wps.client.WPSClientSession;
import org.n52.wps.io.data.IData;
import org.n52.wps.io.data.binding.complex.GTVectorDataBinding;
public class WPSClientExample {
    public void testExecute() {
        String wpsURL = "http://localhost:8080/wps/WebProcessingService";
        String processID = "org.n52.wps.server.algorithm.SimpleBufferAlgorithm";
        try {
            ProcessDescriptionType describeProcessDocument = requestDescribeProcess(
                    wpsURL, processID);
            System.out.println(describeProcessDocument);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        try {
            CapabilitiesDocument capabilitiesDocument = requestGetCapabilities(wpsURL);
            ProcessDescriptionType describeProcessDocument = requestDescribeProcess(
                    wpsURL, processID);
            // define inputs
            HashMap<String, Object> inputs = new HashMap<String, Object>();
            // complex data by reference
            inputs.put(
                    "data",
                    "http://geoprocessing.demo.52north.org:8080/geoserver/ows?service=WFS&version=1.0.0&request=GetFeature&typeName=topp:tasmania_roads&outputFormat=GML3");
            // literal data
            inputs.put("width", "0.05");
            IData data = executeProcess(wpsURL, processID,
                    describeProcessDocument, inputs);
            if (data instanceof GTVectorDataBinding) {
                FeatureCollection featureCollection = ((GTVectorDataBinding) data)
                        .getPayload();
                System.out.println(featureCollection.size());
            }
        } catch (WPSClientException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    public CapabilitiesDocument requestGetCapabilities(String url)
            throws WPSClientException {
        WPSClientSession wpsClient = WPSClientSession.getInstance();
        wpsClient.connect(url);
        CapabilitiesDocument capabilities = wpsClient.getWPSCaps(url);
        ProcessBriefType[] processList = capabilities.getCapabilities()
                .getProcessOfferings().getProcessArray();
        for (ProcessBriefType process : processList) {
            System.out.println(process.getIdentifier().getStringValue());
        }
        return capabilities;
    }
    public ProcessDescriptionType requestDescribeProcess(String url,
            String processID) throws IOException {
        WPSClientSession wpsClient = WPSClientSession.getInstance();
        ProcessDescriptionType processDescription = wpsClient.getProcessDescription(url, processID);
        InputDescriptionType[] inputList = processDescription.getDataInputs()
                .getInputArray();
        for (InputDescriptionType input : inputList) {
            System.out.println(input.getIdentifier().getStringValue());
        }
        return processDescription;
    }
    public IData executeProcess(String url, String processID,
            ProcessDescriptionType processDescription,
            HashMap<String, Object> inputs) throws Exception {
        org.n52.wps.client.ExecuteRequestBuilder executeBuilder = new org.n52.wps.client.ExecuteRequestBuilder(processDescription);
        for (InputDescriptionType input : processDescription.getDataInputs()
                .getInputArray()) {
            String inputName = input.getIdentifier().getStringValue();
            Object inputValue = inputs.get(inputName);
            if (input.getLiteralData() != null) {
                if (inputValue instanceof String) {
                    executeBuilder.addLiteralData(inputName,
                            (String) inputValue);
                }
            } else if (input.getComplexData() != null) {
                // Complexdata by value
                if (inputValue instanceof FeatureCollection) {
                    IData data = new GTVectorDataBinding(
                            (FeatureCollection) inputValue);
                    executeBuilder
                            .addComplexData(
                                    inputName,
                                    data,
                                    "http://schemas.opengis.net/gml/3.1.1/base/feature.xsd",
                                    null, "text/xml");
                }
                // Complexdata Reference
                if (inputValue instanceof String) {
                    executeBuilder
                            .addComplexDataReference(
                                    inputName,
                                    (String) inputValue,
                                    "http://schemas.opengis.net/gml/3.1.1/base/feature.xsd",
                                    null, "text/xml");
                }
                if (inputValue == null && input.getMinOccurs().intValue() > 0) {
                    throw new IOException("Property not set, but mandatory: "
                            + inputName);
                }
            }
        }
        executeBuilder.setMimeTypeForOutput("text/xml", "result");
        executeBuilder.setSchemaForOutput(
                "http://schemas.opengis.net/gml/3.1.1/base/feature.xsd",
                "result");
        ExecuteDocument execute = executeBuilder.getExecute();
        execute.getExecute().setService("WPS");
        WPSClientSession wpsClient = WPSClientSession.getInstance();
        Object responseObject = wpsClient.execute(url, execute);
        if (responseObject instanceof ExecuteResponseDocument) {
            ExecuteResponseDocument response = (ExecuteResponseDocument) responseObject;
            ExecuteResponseAnalyser analyser = new ExecuteResponseAnalyser(
                    execute, response, processDescription);
            IData data = (IData) analyser.getComplexDataByIndex(0,
                    GTVectorDataBinding.class);
            return data;
        }
        throw new Exception("Exception: " + responseObject.toString());
    }
    public static void main(String[] args) {
        WPSClientExample client = new WPSClientExample();
        client.testExecute();
    }
}

测试中出现的问题

出现org.n52.wps.commons.WPSConfig - Can not get java:comp/env context

并报错

ERROR org.n52.wps.client.ExecuteResponseAnalyser - Could not find suitable parser

解决方法

使用wps_config_geotools.xml文件，不要用wps_config.xml
默认会查找src/main/resources下的wps_config.xml，所有可以将wps_config_geotools.xml文件放到resources下并改名为wps_config.xml

或者

// testExecute 方法中
String path = this.getClass().getResource("/").getPath();
// 此处放在 src/main/resources/config 下
WPSConfig.getInstance(path + "config/wps_config_geotools.xml");

本文标题:52°North-WPS-学习-客户端API教程

文章作者:侯志伟 - houzhiwei

发布时间:2017-08-20, 16:40:01

最后更新:2018-05-19, 00:05:34

原始链接:houzw.github.io.git/2017/08/20/52°North-WPS-学习-客户端API教程/

许可协议: "署名-非商用-相同方式共享 4.0" 转载请保留原文链接及作者。