我有简单的XML文件（见下文）
</Students>`<?xml version="1.0" encoding="utf-8"?>
<Students>
<Student id="1">
<id>001</id>
<firstName>John</firstName>
<lastName>Smith</lastName>
</Student>
<Student id="2">
<id>002</id>
<firstName>Jamie</firstName>
<lastName>Lavery</lastName>
</Student>
<Student id="3">
<id>003</id>
<firstName>Emma</firstName>
<lastName>Lavery</lastName>
</Student>
</Students>
`>
我正在尝试将其解析为类型学生的Arraylist然后将其插入到SQL数据库表中......下面是解析器和数据库连接的代码
Student.java
package uk.ac.qub.XML_Parser;
public class Student {
private int id;
private String firstName;
private String lastName;
public Student(){
}
public Student(int id, String firstName, String lastName) {
this.id = id;
this.firstName = firstName;
this.lastName = lastName;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String toString() {
return "ID : " + this.id + "\nFirst Name : "
+ this.firstName + "\nLast Name : " + this.lastName;
}
}
XML_Handler.java
package uk.ac.qub.XML_Parser;
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 XML_Handler extends DefaultHandler {
//List to hold Employees object
private List<Student> studentList = null;
private Student student = null;
//getter method for employee list
public List<Student> getStudentList() {
return studentList;
}
boolean bId = false;
boolean bFirstName = false;
boolean bLastName = false;
@Override
public void startElement(String uri, String localName, String qName, Attributes attributes)
throws SAXException {
if (qName.equalsIgnoreCase("Student")) {
String id = attributes.getValue("id");
//initialize S object and set id attribute
student = new Student();
student.setId(Integer.parseInt(id));
if (studentList == null)
studentList = new ArrayList<>();
} else if (qName.equalsIgnoreCase("id")) {
//set boolean values for fields, will be used in setting variables
bId = true;
} else if (qName.equalsIgnoreCase("firstName")) {
bFirstName = true;
} else if (qName.equalsIgnoreCase("lastName")) {
bLastName = true;
}
}
@Override
public void endElement(String uri, String localName, String qName) throws SAXException {
if (qName.equalsIgnoreCase("Student")) {
//add Employee object to list
studentList.add(student);
}
}
@Override
public void characters(char ch[], int start, int length) throws SAXException {
if (bId) {
//age element, set age
student.setId(Integer.parseInt(new String(ch, start, length)));
bId = false;
} else if (bFirstName) {
student.setFirstName(new String(ch, start, length));
bFirstName = false;
} else if (bLastName) {
student.setLastName(new String(ch, start, length));
bLastName = false;
}
}
}
XML_SAX_Parser.java
package uk.ac.qub.XML_Parser;
import java.io.File;
import java.io.IOException;
import java.util.List;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.SAXException;
public class XML_SAX_Parser {
public void SAX_Parser() {
SAXParserFactory saxParserFactory = SAXParserFactory.newInstance();
try {
SAXParser saxParser = saxParserFactory.newSAXParser();
XML_Handler handler = new XML_Handler();
saxParser.parse(new File(
"c:/users/jamie/desktop/DISSERTATION/student.xml"),
handler);
// Get Student list
List<Student> studentList = handler.getStudentList();
for (Student student : studentList)
System.out.println(student);
} catch (ParserConfigurationException | SAXException | IOException e) {
e.printStackTrace();
}
}
}
DBConnection.java
package uk.ac.qub.DB_Connection;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import uk.ac.qub.XML_Parser.Student;
public class DBConnection {
// this is a local host url.
private static String url = "jdbc:mysql://localhost/test1";
private static String userName = "root";
private static String password = "";
public void startDB(){
List<Student> studentList = new ArrayList<Student>();
connectionDriver();
passinUpdate(studentList);
}
// Enables java to connect to mysql database
public void connectionDriver() {
try {
Class.forName("com.mysql.jdbc.Driver");
System.out.println("Connected to mySQL");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
public void passinUpdate(List<Student> studentList) {
try {
Connection connect2 = DriverManager.getConnection(url, userName,
password);
System.out.println("Established Conenction.....");
String insertStudent = "INSERT INTO Student"
+ "(id, firstName, lastName) VALUES" + "('student.id','student.firstName','student.lastName')";
PreparedStatement statement2 = connect2
.prepareStatement(insertStudent);
statement2.setInt(1, ((Student) studentList).getId());
statement2.setString(2, ((Student) studentList).getFirstName());
statement2.setString(3, ((Student) studentList).getLastName());
statement2.execute();
} catch (SQLException sqlException) {
if (sqlException.getErrorCode() == 1007) {
// Database already exists error
System.out.println(sqlException.getMessage());
} else {
// Some other problems, e.g. Server down, no permission, etc
sqlException.printStackTrace();
}
}
}
}
输出....
Connected to mySQL
Established Conenction.....
Exception in thread "main" java.lang.ClassCastException: java.util.ArrayList cannot be cast to uk.ac.qub.XML_Parser.Student
at uk.ac.qub.DB_Connection.DBConnection.passinUpdate(DBConnection.java:61)
at uk.ac.qub.DB_Connection.DBConnection.startDB(DBConnection.java:25)
at uk.ac.qub.Start.Start_Program.main(Start_Program.java:9)
这是我所知道的很多代码，但真的不确定问题出在哪里.....感谢您的帮助！
答案 0 :(得分：0)
Java告诉您问题的确切位置：
uk.ac.qub.DB_Connection.DBConnection.passinUpdate(DBConnection.java:61)
如果方法passinUpdate的参数是
List<Student> studentList
你不能把它当作
(Student) studentList
做一个循环：
for (Student student : studentList) {
statement2.setInt(1, student.getId());
statement2.setString(2, student.getFirstName());
statement2.setString(3, student.getLastName());
statement2.execute();
}
答案 1 :(得分：0)
您的方法有几个问题
public void passinUpdate(List<Student> studentList) {
try {
Connection connect2 = DriverManager.getConnection("", "",
"");
System.out.println("Established Conenction.....");
//Passing parameters to query
String insertStudent = "INSERT INTO Student" + "(id, firstName, lastName) VALUES" + "(?,?,?)";
//Create a loop for students
for(Student student : studentList){
PreparedStatement statement2 = connect2 .prepareStatement(insertStudent);
//Incorrect cast was used here
statement2.setInt(1, student.getId());
statement2.setString(2, student.getFirstName());
statement2.setString(3, student.getLastName());
statement2.execute();
}
} catch (SQLException sqlException) {
if (sqlException.getErrorCode() == 1007) {
// Database already exists error
System.out.println(sqlException.getMessage());
} else {
// Some other problems, e.g. Server down, no permission, etc
sqlException.printStackTrace();
}
}
}