salesforce 零基礎學習（三十二）經過Streams和DOM方式讀寫XML

時間 2019-11-19

標籤 salesforce 零基礎學習三十二經過 streams dom 方式讀寫 xml 欄目 HTML 简体版

原文原文鏈接

有的時候咱們須要對XML進行讀寫操做，經常使用的XML操做主要有Streams和DOM方式。java

一.Streams方式node

Streams經常使用到的類主要有兩個XmlStreamReader 以及XmlStreamWriter。api

XmlStreamReader:此種讀取方式的讀的特色爲從上而下讀，下圖是根據reader的EventType自上而下的運行步驟。dom

咱們將此xml讀取後封裝到一個Goods的List中，Goods包括item,name以及type屬性，代碼以下：oop

/*
* 假定目前XML數據樣式爲：
*<?xml version="1.0"?>
*<goodsList>
*    <goods item="1">
*        <name>華爲手機</name>
*        <type>華爲</type>
*    </goods>
*    <goods item="2">
*        <name>小米手機</name>
*        <type>小米</type>
*    </goods>
*</goodsList>
* 須要將xml解析成Goods的一個List
*/
public class XmlReaderController {
    public class Goods {
        public String item{get;set;}
        public String name{get;set;}
        public String type{get;set;}
    }
    
    public List<Goods> getGoodsListByXmlFile(String goodsXml) {
        XmlStreamReader reader = new XmlStreamReader(goodsXml);
        Boolean flagXmlEnd = true;
        List<Goods> goodsList = new List<Goods>();
        while(flagXmlEnd) {
            Goods tempGoods;
            if(reader.getEventType() == XmlTag.START_ELEMENT) {
                if(reader.getLocalName().equalsIgnoreCase('goods')) {
                    tempGoods = getGoods(reader);
                }
            }
            
            if(reader.hasNext()) {
                reader.next();
            } else {
                flagXmlEnd = false;
                break;
            }
            if(tempGoods != null) {
                goodsList.add(tempGoods);
            }
        }
        return goodsList;
    }
    
    
    Goods getGoods(XmlStreamReader reader) {
        Goods tempGoods = new Goods();
        tempGoods.item = reader.getAttributeValue(null,'item');
        Boolean flagIsLoop = true;
        while(flagIsLoop) {
            if(reader.hasNext()) {
                reader.next();
                if(reader.getEventType() == XmlTag.START_ELEMENT) {
                    if(reader.getLocalName().equalsIgnoreCase('name')) {
                        reader.next();
                        tempGoods.name = reader.getText();
                    } else if(reader.getLocalName().equalsIgnoreCase('type')) {
                        reader.next();
                        tempGoods.type = reader.getText();
                    }
                }
                if(reader.getEventType() == XmlTag.END_ELEMENT && reader.getLocalName().equalsIgnoreCase('goods')) {
                    flagIsLoop = false;
                    break;
                }
            } else {
                flagIsLoop = false;
                break;
            }
        }
        return tempGoods;
    }
}

在匿名塊測試方法：測試

String goodsXml = '<?xml version="1.0"?>' +
        '<goodsList>' +
            '<goods item="1">' +
                '<name>華爲手機</name>' +
                '<type>華爲</type>' +
            '</goods>' +
            '<goods item="2">' +
                '<name>小米手機</name>' +
                '<type>小米</type>' +
            '</goods>' +
        '</goodsList>';
List<XmlReaderController.Goods> goodsList = new XmlReaderController().getGoodsListByXmlFile(goodsXml);
System.debug(JSON.serialize(goodsList));

顯示結果：spa

[
{
"type":"華爲",
"name":"華爲手機",
"item":"1"
},
{
"type":"小米",
"name":"小米手機",
"item":"2"
}

XmlStreamWriter：處理過程同XmlStreamReader，須要從上到下進行寫入，例如若是寫出上述的xml文件，須要先startDocument,而後再startElement.....要注意每一個start須要對應相應的end方法。debug

public class XmlWriterController {
    
    public static void writeXml() {
        XmlStreamWriter writer = new XmlStreamWriter();
        writer.writeStartDocument('utf-8','1.0');
        writer.writeComment('goodsList start here');
        writer.writeStartElement('','goodsList','http://www.goods.com');
        writer.writeNamespace('', 'http://www.goods.com'); 
        writer.writeStartElement(null,'goods',null);
        writer.writeAttribute(null,null,'item','1');
        writer.writeStartElement(null,'name',null);
        writer.writeCharacters('華爲手機');
        writer.writeEndElement();
        writer.writeStartElement(null,'type',null);
        writer.writeCharacters('華爲');
        writer.writeEndElement();
        writer.writeEndElement();
        writer.writeStartElement(null,'goods',null);
        writer.writeAttribute(null,null,'item','2');
        writer.writeStartElement(null,'name',null);
        writer.writeCharacters('小米手機');
        writer.writeEndElement();
        writer.writeStartElement(null,'type',null);
        writer.writeCharacters('小米');
        writer.writeEndElement();
        writer.writeEndElement();
        writer.writeEndElement();
        writer.writeEndDocument();
        system.debug(writer.getXmlString());
    }
}

二.Dom解析code

dom解析原理同java對於dom解析相同，這裏，goodsList做爲根節點，goodsList的子節點有goods1,goods.他們分別有屬性item1和item2，goods1以及goods2又分別有相應的子節點。xml

經過dom方式將上述xml解析成Goods的List。

public class DomXmlController {
    public class Goods {
        String item{get;set;}
        String name{get;set;}
        String type{get;set;}
    }
    public List<Goods> getGoodsViaXmlDom(String xmlString) {
        Dom.Document document = new Dom.Document();
        document.load(xmlString);
        Dom.XmlNode rootElement = document.getRootElement();
        List<Goods> goodsList = new List<Goods>();
        for(Dom.XmlNode node : rootElement.getChildElements()) {
            if(node.getName().equalsIgnoreCase('goods')) {
                Goods tempGoods = new Goods();
                tempGoods = getGoodsNameAndType(node);
                tempGoods.item = node.getAttribute('item',null);
                goodsList.add(tempGoods);
            }
        }
        
        return goodsList;
    }
    
    Goods getGoodsNameAndType(Dom.XmlNode parentNode) {
        transient Goods tempGoods = new Goods();
        for(Dom.XmlNode node : parentNode.getChildElements()) {
            if(node.getName().equalsIgnoreCase('name')) {
                tempGoods.name = node.getText();
            } else if(node.getName().equalsIgnoreCase('type')) {
                tempGoods.type = node.getText();
            }
        }
        return tempGoods;
    }
}

匿名塊測試內容以下：

String goodsXml = '<?xml version="1.0"?>' +
        '<goodsList>' +
            '<goods item="1">' +
                '<name>華爲手機</name>' +
                '<type>華爲</type>' +
            '</goods>' +
            '<goods item="2">' +
                '<name>小米手機</name>' +
                '<type>小米</type>' +
            '</goods>' +
            
        '</goodsList>';
System.debug(JSON.serialize(new DomXmlController().getGoodsViaXmlDom(goodsXml)));

顯示結果：

總結：apex對於xml操做和java很相似，或者說大部分都是從java過來的，若是java解析xml很嫺熟狀況下，使用apex解析xml只須要看看方法就OK了。本篇只是描述最簡單的xml操做，篇中好多方法沒有使用到，有興趣的或者想深刻的能夠本身看一下相關的api。