使用 Java 将 RSS Feed XML 转换为 JSON 仅显示最后一个条目

Question

假设我有一个 RSS Feed（采用 XML 格式），看起来像这样：

<?xml version="1.0" encoding="UTF-8"?>
<rss version="2.0" xmlns:content="http://purl.org/rss/1.0/modules/content/"
    xmlns:wfw="http://wellformedweb.org/CommentAPI/" xmlns:dc="http://purl.org/dc/elements/1.1/"
    xmlns:atom="http://www.w3.org/2005/Atom" xmlns:sy="http://purl.org/rss/1.0/modules/syndication/"
    xmlns:slash="http://purl.org/rss/1.0/modules/slash/">

    <channel>
        <title>MyFeed</title>
        <atom:link href="http://samplefeed.com/feed/" rel="self"
            type="application/rss+xml" />
        <link>http://samplefeed.com</link>
        <description></description>
        <lastBuildDate>Fri, 22 Sep 2017 22:43:51 +0000</lastBuildDate>
        <language>en-US</language>
        <sy:updatePeriod>hourly</sy:updatePeriod>
        <sy:updateFrequency>1</sy:updateFrequency>
        <generator>http://wordpress.org/?v=4.3.12</generator>
        <item>
            <title>A Good Product</title>
            <link>http://samplefeed.com/a-good-product/</link>
            <comments>http://samplefeed.com/a-good-product/#comments</comments>
            <pubDate>Wed, 20 Sep 2017 22:22:45 +0000</pubDate>
            <dc:creator><![CDATA[John Smith]]></dc:creator>
            <category><![CDATA[Entertainment]]></category>

            <guid isPermaLink="false">http://samplefeed.com/?p=9116</guid>
            <description>
                <![CDATA[<p>![CDATA[<p>9/22</p>
                <p>4K TV Samsung<br />
                Price: 0.00<br />
                Location: Walmart</p>
                ]]>
            </description>
        </item>
        <!-- More items -->
    </channel>
</rss>

采纳了 varren 的建议，但它 returns 最后一个条目而不是所有条目...

public static void main(String[] args) throws MalformedURLException, IOException {
    XmlMapper xmlMapper = new XmlMapper(); // <- This is line 21 
    ObjectMapper jsonMapper = new ObjectMapper();
    InputStream xml = getInputStreamFromUrlData("http://samplefeed.com/feed");
    String json = jsonMapper.writeValueAsString(xmlMapper.readTree(xml));
    System.out.println(json);       
}

public static InputStream getInputStreamForURLData(String Url) {
    URL url = null;
    HttpURLConnection httpConnection = null;
    InputStream content = null;

    try {
        url = new URL(Url);
        System.out.println("URL: " + Url);
        URLConnection conn = url.openConnection();
        conn.setRequestProperty("User-Agent", "Mozilla/5.0");
        httpConnection = (HttpURLConnection) conn;

        int responseCode = httpConnection.getResponseCode();
        System.out.println("Response Code : " + responseCode);

        content = (InputStream) httpConnection.getInputStream();
    } 
    catch (MalformedURLException e) {
        e.printStackTrace();
    } 
    catch (IOException e) {
        e.printStackTrace();
    }
    return content;
}

pom.xml:

    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-annotations</artifactId>
        <version>2.9.1</version>
    </dependency>

    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-core</artifactId>
        <version>2.9.1</version>
    </dependency>

    <dependency>
        <groupId>org.codehaus.jackson</groupId>
        <artifactId>jackson-core-asl</artifactId>
        <version>1.7.9</version>
    </dependency>

    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.8.10</version>
    </dependency>

    <dependency>
        <groupId>org.codehaus.jackson</groupId>
        <artifactId>jackson-mapper-asl</artifactId>
        <version>1.7.9</version>
    </dependency>

    <dependency>
        <groupId>org.codehaus.jackson</groupId>
        <artifactId>jackson-xc</artifactId>
        <version>1.7.9</version>
    </dependency>

    <dependency>
        <groupId>com.fasterxml.jackson.dataformat</groupId>
        <artifactId>jackson-dataformat-xml</artifactId>
        <version>2.9.1</version>
    </dependency>

现在的问题是它只返回 RSS Feed 中的最后一项而不是全部？！？它确实将其生成为 JSON 但仅显示最后一个条目。

为什么不显示所有条目？

谁能提出不同的方法（例如，如何使用 Rome 或直接 DOM 来做到这一点）？

Answer 1

可以将 Jackson 与 xml 依赖项一起使用：

compile 'com.fasterxml.jackson.core:jackson-databind:2.9.1'
compile 'com.fasterxml.jackson.core:jackson-core:2.9.1'
compile 'com.fasterxml.jackson.dataformat:jackson-dataformat-xml:2.9.1' // <= that

简单的用例看起来像（实际上您可以使用自定义 POJO 和大量注释或手动映射 xml attributes/prefixes 到一些 json 值来自定义几乎所有内容）：

public class Main4 {
  public static void main(String[] args) throws Exception {
    XmlMapper xmlMapper = new XmlMapper();
    ObjectMapper jsonMapper = new ObjectMapper();
    InputStream XML = Main4.class.getClassLoader()
            .getResourceAsStream("rss.xml");
    String json = jsonMapper.writeValueAsString(xmlMapper.readTree(XML));
    System.out.println(json);
  }
}

结果：

{
  "version": "2.0",
  "channel": {
    "title": "MyFeed",
    "link": "http://samplefeed.com",
    "description": "",
    "lastBuildDate": "Fri, 22 Sep 2017 22:43:51 +0000",
    "language": "en-US",
    "updatePeriod": "hourly",
    "updateFrequency": "1",
    "generator": "http://wordpress.org/?v=4.3.12",
    "item": {
      "title": "A Good Product",
      "link": "http://samplefeed.com/a-good-product/",
      "comments": "http://samplefeed.com/a-good-product/#comments",
      "pubDate": "Wed, 20 Sep 2017 22:22:45 +0000",
      "creator": "John Smith",
      "category": "Entertainment",
      "guid": {
        "isPermaLink": "false",
        "": "http://samplefeed.com/?p=9116"
      },
      "description": "\n                <p>![CDATA[<p>9/22</p>\n                <p>4K TV Samsung<br />\n                Price: 0.00<br />\n                Location: Walmart</p>\n                \n            "
    }
  }
}

Answer 2

其他人在使用 Jackson 将 xml 转换为 json 时也遇到了问题，并且只得到了最后一个元素：Converting xml to json using jackson

因此，您可以尝试 JSON in Java:

而不是 Jackson

<dependency>
    <groupId>org.json</groupId>
    <artifactId>json</artifactId>
    <version>20170516</version>
</dependency>

示例代码

import java.io.*;
import java.net.*;
import org.json.JSONObject;
import org.json.XML;
...
public static void main(String[] args) throws Exception {
    String xmlString = readUrlToString("http://www.feedforall.com/sample.xml");
    JSONObject xmlJSONObj = XML.toJSONObject(xmlString);
    String jsonPrettyPrintString = xmlJSONObj.toString(4);
    System.out.println(jsonPrettyPrintString);
}

public static String readUrlToString(String url) {
    BufferedReader reader = null;
    String result = null;
    try {
        URL u = new URL(url);
        HttpURLConnection conn = (HttpURLConnection) u.openConnection();
        conn.setRequestProperty("User-Agent", "Mozilla/5.0");
        conn.setRequestMethod("GET");
        conn.setDoOutput(true);
        conn.setReadTimeout(2 * 1000);
        conn.connect();
        reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
        StringBuilder builder = new StringBuilder();
        String line;
        while ((line = reader.readLine()) != null) {
            builder.append(line).append("\n");
        }
        result = builder.toString();
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        if (reader != null) {
            try { reader.close(); } catch (IOException ignoreOnClose) { }
        }
    }
    return result;
}

另请参阅：Quickest way to convert XML to JSON in Java

Answer 3

Why doesn't it display all of entries?

XML不区分"Objects"和"Arrays"的概念，因此只打印单个item，而不是所有项目。

这是解决方法，除了您正在使用的依赖项之外，我还使用了 2 个额外的 jar，它们如下所示：-

java-json.jar : http://www.java2s.com/Code/Jar/j/Downloadjavajsonjar.htm
commons-io : https://mvnrepository.com/artifact/commons-io/commons-io/2.4

您的代码：

import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;

import org.apache.commons.io.IOUtils;
import org.json.JSONObject;
import org.json.XML;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;

public class TestClass {

    public static void main(String[] args) throws Exception {
        InputStream xml = getInputStreamFromUrlData("http://www.feedforall.com/sample.xml");
        String xmlString = IOUtils.toString(xml);
        JSONObject jsonObject = XML.toJSONObject(xmlString);
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.enable(SerializationFeature.INDENT_OUTPUT);
        Object json = objectMapper.readValue(jsonObject.toString(), Object.class);
        String output = objectMapper.writeValueAsString(json);
        System.out.println(output);
    }

    public static InputStream getInputStreamFromUrlData(String Url) {
        URL url = null;
        HttpURLConnection httpConnection = null;
        InputStream content = null;

        try {
            url = new URL(Url);
            System.out.println("URL: " + Url);
            URLConnection conn = url.openConnection();
            conn.setRequestProperty("User-Agent", "Mozilla/5.0");
            httpConnection = (HttpURLConnection) conn;

            int responseCode = httpConnection.getResponseCode();
            System.out.println("Response Code : " + responseCode);

            content = (InputStream) httpConnection.getInputStream();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return content;
    }
}

示例运行：（检查item是对象数组而不是单个对象）

URL: http://www.feedforall.com/sample.xml
Response Code : 200
{
  "rss" : {
    "channel" : {
      "image" : {
        "link" : "http://www.feedforall.com/industry-solutions.htm",
        "width" : 48,
        "description" : "FeedForAll Sample Feed",
        "title" : "FeedForAll Sample Feed",
        "url" : "http://www.feedforall.com/ffalogo48x48.gif",
        "height" : 48
      },
      "copyright" : "Copyright 2004 NotePage, Inc.",
      "item" : [ {
        "comments" : "http://www.feedforall.com/forum",
        "link" : "http://www.feedforall.com/restaurant.htm",
        "description" : "<b>FeedForAll </b>helps Restaurant's communicate with customers. Let your customers know the latest specials or events.<br>\r\n<br>\r\nRSS feed uses include:<br>\r\n<i><font color=\"#FF0000\">Daily Specials <br>\r\nEntertainment <br>\r\nCalendar of Events </i></font>",
        "title" : "RSS Solutions for Restaurants",
        "category" : {
          "domain" : "www.dmoz.com",
          "content" : "Computers/Software/Internet/Site Management/Content Management"
        },
        "pubDate" : "Tue, 19 Oct 2004 11:09:11 -0400"
      }, {
        "comments" : "http://www.feedforall.com/forum",
        "link" : "http://www.feedforall.com/schools.htm",
        "description" : "FeedForAll helps Educational Institutions communicate with students about school wide activities, events, and schedules.<br>\r\n<br>\r\nRSS feed uses include:<br>\r\n<i><font color=\"#0000FF\">Homework Assignments <br>\r\nSchool Cancellations <br>\r\nCalendar of Events <br>\r\nSports Scores <br>\r\nClubs/Organization Meetings <br>\r\nLunches Menus </i></font>",
        "title" : "RSS Solutions for Schools and Colleges",
        "category" : {
          "domain" : "www.dmoz.com",
          "content" : "Computers/Software/Internet/Site Management/Content Management"
        },
        "pubDate" : "Tue, 19 Oct 2004 11:09:09 -0400"
      }, {
        "comments" : "http://www.feedforall.com/forum",
        "link" : "http://www.feedforall.com/computer-service.htm",
        "description" : "FeedForAll helps Computer Service Companies communicate with clients about cyber security and related issues. <br>\r\n<br>\r\nUses include:<br>\r\n<i><font color=\"#0000FF\">Cyber Security Alerts <br>\r\nSpecials<br>\r\nJob Postings </i></font>",
        "title" : "RSS Solutions for Computer Service Companies",
        "category" : {
          "domain" : "www.dmoz.com",
          "content" : "Computers/Software/Internet/Site Management/Content Management"
        },
        "pubDate" : "Tue, 19 Oct 2004 11:09:07 -0400"
      }, {
        "comments" : "http://www.feedforall.com/forum",
        "link" : "http://www.feedforall.com/government.htm",
        "description" : "FeedForAll helps Governments communicate with the general public about positions on various issues, and keep the community aware of changes in important legislative issues. <b><i><br>\r\n</b></i><br>\r\nRSS uses Include:<br>\r\n<i><font color=\"#00FF00\">Legislative Calendar<br>\r\nVotes<br>\r\nBulletins</i></font>",
        "title" : "RSS Solutions for Governments",
        "category" : {
          "domain" : "www.dmoz.com",
          "content" : "Computers/Software/Internet/Site Management/Content Management"
        },
        "pubDate" : "Tue, 19 Oct 2004 11:09:05 -0400"
      }, {
        "comments" : "http://www.feedforall.com/forum",
        "link" : "http://www.feedforall.com/politics.htm",
        "description" : "FeedForAll helps Politicians communicate with the general public about positions on various issues, and keep the community notified of their schedule. <br>\r\n<br>\r\nUses Include:<br>\r\n<i><font color=\"#FF0000\">Blogs<br>\r\nSpeaking Engagements <br>\r\nStatements<br>\r\n </i></font>",
        "title" : "RSS Solutions for Politicians",
        "category" : {
          "domain" : "www.dmoz.com",
          "content" : "Computers/Software/Internet/Site Management/Content Management"
        },
        "pubDate" : "Tue, 19 Oct 2004 11:09:03 -0400"
      }, {
        "comments" : "http://www.feedforall.com/forum",
        "link" : "http://www.feedforall.com/weather.htm",
        "description" : "FeedForAll helps Meteorologists communicate with the general public about storm warnings and weather alerts, in specific regions. Using RSS meteorologists are able to quickly disseminate urgent and life threatening weather warnings. <br>\r\n<br>\r\nUses Include:<br>\r\n<i><font color=\"#0000FF\">Weather Alerts<br>\r\nPlotting Storms<br>\r\nSchool Cancellations </i></font>",
        "title" : "RSS Solutions for Meteorologists",
        "category" : {
          "domain" : "www.dmoz.com",
          "content" : "Computers/Software/Internet/Site Management/Content Management"
        },
        "pubDate" : "Tue, 19 Oct 2004 11:09:01 -0400"
      }, {
        "comments" : "http://www.feedforall.com/forum",
        "link" : "http://www.feedforall.com/real-estate.htm",
        "description" : "FeedForAll helps Realtors and Real Estate companies communicate with clients informing them of newly available properties, and open house announcements. RSS helps to reach a targeted audience and spread the word in an inexpensive, professional manner. <font color=\"#0000FF\"><br>\r\n</font><br>\r\nFeeds can be used for:<br>\r\n<i><font color=\"#FF0000\">Open House Dates<br>\r\nNew Properties For Sale<br>\r\nMortgage Rates</i></font>",
        "title" : "RSS Solutions for Realtors & Real Estate Firms",
        "category" : {
          "domain" : "www.dmoz.com",
          "content" : "Computers/Software/Internet/Site Management/Content Management"
        },
        "pubDate" : "Tue, 19 Oct 2004 11:08:59 -0400"
      }, {
        "comments" : "http://www.feedforall.com/forum",
        "link" : "http://www.feedforall.com/banks.htm",
        "description" : "FeedForAll helps <b>Banks, Credit Unions and Mortgage companies</b> communicate with the general public about rate changes in a prompt and professional manner. <br>\r\n<br>\r\nUses include:<br>\r\n<i><font color=\"#0000FF\">Mortgage Rates<br>\r\nForeign Exchange Rates <br>\r\nBank Rates<br>\r\nSpecials</i></font>",
        "title" : "RSS Solutions for Banks / Mortgage Companies",
        "category" : {
          "domain" : "www.dmoz.com",
          "content" : "Computers/Software/Internet/Site Management/Content Management"
        },
        "pubDate" : "Tue, 19 Oct 2004 11:08:57 -0400"
      }, {
        "comments" : "http://www.feedforall.com/forum",
        "link" : "http://www.feedforall.com/law-enforcement.htm",
        "description" : "<b>FeedForAll</b> helps Law Enforcement Professionals communicate with the general public and other agencies in a prompt and efficient manner. Using RSS police are able to quickly disseminate urgent and life threatening information. <br>\r\n<br>\r\nUses include:<br>\r\n<i><font color=\"#0000FF\">Amber Alerts<br>\r\nSex Offender Community Notification <br>\r\nWeather Alerts <br>\r\nScheduling <br>\r\nSecurity Alerts <br>\r\nPolice Report <br>\r\nMeetings</i></font>",
        "title" : "RSS Solutions for Law Enforcement",
        "category" : {
          "domain" : "www.dmoz.com",
          "content" : "Computers/Software/Internet/Site Management/Content Management"
        },
        "pubDate" : "Tue, 19 Oct 2004 11:08:56 -0400"
      } ],
      "lastBuildDate" : "Tue, 19 Oct 2004 13:39:14 -0400",
      "link" : "http://www.feedforall.com/industry-solutions.htm",
      "description" : "RSS is a fascinating technology. The uses for RSS are expanding daily. Take a closer look at how various industries are using the benefits of RSS in their businesses.",
      "generator" : "FeedForAll Beta1 (0.0.1.8)",
      "language" : "en-us",
      "title" : "FeedForAll Sample Feed",
      "managingEditor" : "marketing@feedforall.com",
      "pubDate" : "Tue, 19 Oct 2004 13:38:55 -0400",
      "webMaster" : "webmaster@feedforall.com",
      "docs" : "http://blogs.law.harvard.edu/tech/rss",
      "category" : {
        "domain" : "www.dmoz.com",
        "content" : "Computers/Software/Internet/Site Management/Content Management"
      }
    },
    "version" : 2
  }
}

Answer 4

得到这样的效果：

@RequestMapping(value = "/v2/convertIntoJson", 
                method = RequestMethod.GET, 
                produces = "application/json")
public String getRssFeedAsJson() throws IOException {
    InputStream xml = getInputStreamForURLData("http://www.samplefeed.com/feed/");
    byte[] byteArray = IOUtils.toByteArray(xml);
    String xmlString = new String(byteArray);
    JSONObject xmlToJsonObject = XML.toJSONObject(xmlString);
    String jsonString = xmlToJsonObject.toString();
    byte[] jsonStringAsByteArray = jsonString.getBytes("UTF-8");
    String retValue = new String(jsonStringAsByteArray, "UTF-8");
    return retValue;
}

public static InputStream getInputStreamForURLData(String Url) {
    URL url = null;
    HttpURLConnection httpConnection = null;
    InputStream content = null;

    try {
        url = new URL(Url);
        System.out.println("URL::" + Url);
        URLConnection conn = url.openConnection();
        conn.setRequestProperty("User-Agent", "Mozilla/5.0");
        httpConnection = (HttpURLConnection) conn;

        int responseCode = httpConnection.getResponseCode();
        System.out.println("Response Code : " + responseCode);

        content = (InputStream) httpConnection.getInputStream();
    } 
    catch (MalformedURLException e) {
        e.printStackTrace();
    } 
    catch (IOException e) {
        e.printStackTrace();
    }
    return content;
}

使用 Java 将 RSS Feed XML 转换为 JSON 仅显示最后一个条目

Convert RSS Feed XML to JSON using Java Displays only Last Entry

java

xml

rss

json

jackson