SAX 解析器 - 如何处理来自 .XML 文件的不良数据答案

【问题标题】：SAX Parser - How To Handle Bad Data From .XML FileSAX 解析器 - 如何处理来自 .XML 文件的不良数据
【发布时间】：2016-04-07 19:47:07
【问题描述】：

我需要制作一个程序，该程序需要一个 .xml 文件，该文件使用 Java 中的 SAX Parser 来解析 .xml 文件，将其存储在 arrayList 中，然后调用方法以使用 arrayList 显示某些对象。

我的程序需要能够处理向 SAX Parser 提供错误数据的用户，这样如果它没有它正在寻找的特定标签，那么它就不会中断。我需要它能够加载数据并使用“检查”命令来检查数据的完整性。例如，如果客户没有与之关联的帐户，程序将输出哪个客户没有帐户。

下面，我把程序的任务，Handler，以及数据不好的.xml放在下面。

程序的任务：

check ：此命令用于检查命名条目的完整性。换句话说，它检查给定类型的所有条目是否正确。例如，如果命令是：检查客户该程序应列出所有没有任何帐户的客户（名字和姓氏）。相关命令包括：检查帐户：列出没有关联地址的任何帐号检查地址：列出没有关联仪表的任何地址 check Meter : 列出任何没有任何仪表读数的仪表 ID，或者其读数与仪表类型不匹配，例如，从轮询仪表推送读数。

.xml 文件：

 <xml version="1.0" encoding="UTF-8">
    <!-- Customer with no account -->
    <customer lastName ="Anderson" firstName="Thomas">

    </customer>

    <!-- Account with no address -->    
    <customer lastName ="Baker" firstName="Susanne">
        <account type="residential" accountNumber="999-999-99">              
        </account>
    </customer>

    <!-- Address with no meter -->    
    <customer lastName ="Charles" firstName="Henry">
        <account type="residential" accountNumber="888-888-88">   
            <address type="apartment" unit="308" street="E 6th St." number="56" zipCode="13126"/>           
        </account>
    </customer>

    <!-- Meter with no readings -->    
    <customer lastName ="Davidson" firstName="Mary">
        <account type="residential" accountNumber="666-666-66">   
            <address type="apartment" unit="308" street="W 9th St." number="67" zipCode="13126">
                <meter id = "RM-4876-X4" brand="GE" type="poll" location = "West side of building"/>
            </address>           
        </account>
    </customer>

    <!-- Meter with mismatched readings -->    
    <customer lastName ="Evans" firstName="Oscar">
        <account type="residential" accountNumber="555-555-55">   
            <address type="house" street="E 10th St." number="78" zipCode="13126">
                <meter id = "RM-4874-X4" brand="GE" type="poll" location = "North side">
                    <meterReading reading="650" date = "1413227815" flag="poll"/>
                    <meterReading reading="675" date = "1413314215" flag="push"/>
                    <meterReading reading="622" date = "1413400615" flag="poll"/>
                </meter>
            </address>           
        </account>
    </customer>
</xml>

处理程序文件：

    package csc241hw07;

import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.ZoneOffset;
import java.util.ArrayList;
import java.util.List;

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

public class MyHandler extends DefaultHandler {

    // Variables to hold current values
    private ArrayList<Customer> customerList = new ArrayList<Customer>();
    private Customer currentCustomer;
    private Account currentAccount;
    private Address currentAddress;
    private Meter currentMeter;

    //getter method for employee list
    public ArrayList<Customer> getCustList() {
        return customerList;
    }

    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes)
            throws SAXException {

        if (qName.equalsIgnoreCase("customer")) {
            //Create a customer object
            String lastName = attributes.getValue("lastName");
            String firstName = attributes.getValue("firstName");
            currentCustomer = new Customer(lastName, firstName);

        } else if (qName.equalsIgnoreCase("address")) {
            // Create an Address object
            String street = attributes.getValue("street");
            int houseNumber = Integer.parseInt(attributes.getValue("number"));
            String zipCode = attributes.getValue("zipCode");
            String type = attributes.getValue("type");
            String unit = attributes.getValue("unit");

            if (type.equalsIgnoreCase("mailing")) {
                // this is a mailing address -- assign to current customer
                MailingAddress ma = new MailingAddress(street, houseNumber, zipCode, type);
                currentCustomer.setMailingAddress(ma);
            } else if (type.equalsIgnoreCase("house")) {
                // Create a house
                currentAddress = new House(street, houseNumber, zipCode, type);
            } else if (type.equalsIgnoreCase("commercial")) {
                // Create a commercial
                currentAddress = new Commercial(street, houseNumber, zipCode, type);
            } else if (unit != null) {
                // Create an apartment
                currentAddress = new Apartment(street, houseNumber, zipCode, type, unit);
            } else {
                System.out.println("Unknown address type:" + type);
            }


            if (currentAddress != null) {
                // Assign this account to current address
                currentAddress.setAccount(currentAccount);
                currentAccount.addAddress(currentAddress);
            }

        } else if (qName.equalsIgnoreCase("meter")) {
            // Create a meter object
            String type = attributes.getValue("type");
            String brand = attributes.getValue("brand");
            String id = attributes.getValue("id");
            if (type.equalsIgnoreCase("push")) {
                currentMeter = new PushMeter(id, brand, type);
            } else if (type.equalsIgnoreCase("poll")) {
                currentMeter = new PollMeter(id, brand, type);
            } else {
                System.out.println("Unknown meter type: " + type);
            }


            if (currentMeter != null) {
                // Set location
                String location = attributes.getValue("location");
                currentMeter.setLocation(currentAddress, location);
                currentAddress.addMeter(currentMeter);
            }

            //System.out.println("METER:");
        } else if (qName.equalsIgnoreCase("meterReading")) {
            // Create a meter reading
            //<meterReading reading="622" date = "1413400615" flag="push"/>
            double reading = Double.parseDouble(attributes.getValue("reading"));
            //System.out.println("DATE:" );
            ZoneOffset z = ZoneOffset.ofHours(5);
            long epoch = Long.parseLong(attributes.getValue("date"));
            LocalDateTime d = LocalDateTime.ofEpochSecond(epoch,0,z);
            //System.out.println("DATE:" + d.toString());
            String flag = attributes.getValue("flag");
            MeterReading mr = new MeterReading(reading, d, flag, currentMeter);
            // Add this to current meter
            currentMeter.addReading(mr);
            //System.out.println("METERREADING:");

        } else if (qName.equalsIgnoreCase("account")) {
//    <account type="residential" accountNumber="876-543-21">
            String type = attributes.getValue("type");
            String acctNum = attributes.getValue("accountNumber");
            if (type.equalsIgnoreCase("residential")) {
                // residential account
                currentAccount = new ResidentialAccount(acctNum, currentCustomer);
            } else if (type.equalsIgnoreCase("commercial")) {
                currentAccount = new CommercialAccount(acctNum, currentCustomer);
            } else {
                System.out.println("Unknown account type:" + type);
            }

            if (currentAccount != null) {
                // Add this account to current customer
                currentCustomer.addAccount(currentAccount);
            }
        }
    }

    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        if (qName.equalsIgnoreCase("customer")) {
            customerList.add(currentCustomer);
            currentCustomer = null;
        } else if (qName.equalsIgnoreCase("meter")) {
            currentMeter = null;
        } else if (qName.equalsIgnoreCase("account")) {
            currentAccount = null;
        } else if (qName.equalsIgnoreCase("address")) {
            currentAddress = null;
        }
    }
}

谢谢！

【问题讨论】：

您研究过 JaxB 吗？它优雅地处理丢失的标签。它不会处理格式错误的 xml，但我认为这不是您想要的。无需全部手动编写。
要回答的问题是什么？
我要问的问题是：如果解析器正在寻找某个标签但找不到它，我如何向用户显示他们正在使用的 .xml 文件不包含标记？

标签： java xml

【解决方案1】：

您可以再添加一个包含“不良”客户的列表，例如：

// Variables to hold current values
private ArrayList<Customer> customerList = new ArrayList<Customer>();
private ArrayList<Customer> badCustomerList = new ArrayList<Customer>();
...

并添加一些更改，将这些客户从“好”客户中分出。例如：

@Override
public void endElement(String uri, String localName, String qName) throws SAXException {
    if (qName.equalsIgnoreCase("customer")) {
        if (isCustomerGood(currentCustomer)) {      // Here is checking code
            customerList.add(currentCustomer);
        } else {
            badCustomerList.add(currentCustomer);
        }
        currentCustomer = null;
    } else if (qName.equalsIgnoreCase("meter")) {
        currentMeter = null;
    } else if (qName.equalsIgnoreCase("account")) {
        currentAccount = null;
    } else if (qName.equalsIgnoreCase("address")) {
        currentAddress = null;
    }
}

private static boolean isCustomerGood(Customer customer) {
    return customer.getAccount() != null;
}

public boolean check() {
    return badCustomerList.isEmpty();
}

public List<Customer> getBadCustomers() {
    return badCustomerList;
}

实际上，您可以根据需要以不同的方式实现isCustomerGood。现在您只需在解析结束时运行check 方法即可。

【讨论】：

【解决方案2】：

首先，我认为您所说的数据不正确并不是指导致解析异常的非格式良好的 XML 文件。

如果上述假设成立，那么我认为你应该考虑使用XPath来查询数据文件并检查目标元素不存在的情况......

那么你为什么不使用 XPath 来让你的代码更容易编写和维护呢？

【讨论】：