SAX Parser - 如何处理来自.XML文件的错误数据

Question

I need to make a program that takes an .xml file that uses the SAX Parser in Java to parse the .xml file, store it in an arrayList and then call methods to display certain objects with the arrayList.

My program needs to be able to handle the user giving the SAX Parser bad data such that if it doesn't have a certain tag it's looking for, then it won't break. I need it to be able to load the data and use a “check” command to check the intergrity of the data. For example, if the customer doest't have an account associated with it, the program will output which customer doesn't have an account.

Below, I've put the task for the program, the Handler, and the .xml with bad data below.

Task for the program:

check : This command is used to check the integrity of the named entries. In other words, it checks to see that all the entries of a given type are correct. For example, if the command is: check customer the program should list all customers (first name and last name) that do not have any accounts. Related commands include: check account : list any account number without an associated address check address : list any address without an associated meter check meter : list any meter id without any meter readings, or whose readings do not match the meter type, eg, push reading from a polling meter.

.xml File:

 <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>

Handler File:

    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;
        }
    }
}

Thank you!

Answer 1

You can add one more list with "bad" customers like:

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

And add some changes sorting those customers out of "good" ones. For instance:

@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;
}

Actually you can implement isCustomerGood differently depending on your needs. Now you just run check method at the end of parsing.

Answer 2

First of all, by bad data I dont think you mean a non-wellformed XML file that causes parsing exception.

If the above assumption is true, then I think you should consider using XPath to query the data file and check for the condition where the target element does not exist...

So why are you not using XPath which would make your code a lot easier to write and maintain?