更新
提供的代码可将ResultSet 中的数据正确提取到JAXB 使用的对象中。
创建xml 文件不需要HashMap 和/或List 或HashMap
只要您创建了正确的数据对象，您就可以使用 JAXB 轻松完成此操作。
首先，创建classes 以匹配xml 中所需的结构。
- 一个
ScoreRecord 类，其中包含课程名称和标记等课程信息。
- 一个
Student 类，其中包含学生信息，例如名字、姓氏和ScoreRecords 对象列表。
-
StudentGroup 班级，其中包含属于同一教师组的所有学生
ScoreRecord 类：
import java.math.BigDecimal;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;
@XmlRootElement(name = "Mark")
@XmlType(propOrder = { "sub", "percent" })
public class ScoreRecord {
private String sub;
private String percent;
public void setSub(String sub) {
this.sub = sub;
}
public String getSub() {
return sub;
}
public void setPercent(String percent) {
this.percent = percent;
}
public String getPercent() {
return percent;
}
}
Student 类：
import java.util.List;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElementWrapper;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;
@XmlRootElement(name = "Student")
@XmlType(propOrder = { "firstName", "lastName", "id", "scoreRecords" })
public class Student {
private Integer id;
private String firstName;
private String lastName;
private List<ScoreRecord> scoreRecords;
public void setId(Integer id) {
this.id = id;
}
@XmlElement(name = "Id")
public Integer getId() {
return id;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
@XmlElement(name = "FirstName")
public String getFirstName() {
return firstName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
@XmlElement(name = "LastName")
public String getLastName() {
return lastName;
}
public void setScoreRecords(List<ScoreRecord> scoreRecords) {
this.scoreRecords = scoreRecords;
}
@XmlElementWrapper(name = "MarksList")
@XmlElement(name = "Mark")
public List<ScoreRecord> getScoreRecords() {
return scoreRecords;
}
}
StudentGroup 类：
import java.util.List;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElementWrapper;
import javax.xml.bind.annotation.XmlRootElement;
@XmlRootElement(name = "Records")
public class StudentGroup {
private List<Student> students;
public void setStudents(List<Student> students) {
this.students = students;
}
@XmlElement(name = "StudentRecord")
public List<Student> getStudents() {
return students;
}
}
现在，创建一个类来“按原样”保存数据库中的数据
public class DbStudent {
private String firstName;
private String lastName;
private Integer id;
private String sub;
private String percent;
public DbStudent(String firstName, String lastName, int id, String sub, String percent) {
this.firstName = firstName;
this.lastName = lastName;
this.id = id;
this.sub = sub;
this.percent = percent;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getFirstName() {
return firstName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getLastName() {
return lastName;
}
public void setId(Integer id) {
this.id = id;
}
public Integer getId() {
return id;
}
public void setSub(String sub) {
this.sub = sub;
}
public String getSub() {
return sub;
}
public void setPercent(String percent) {
this.percent = percent;
}
public String getPercent() {
return percent;
}
}
创建一个方法来检索作为此对象类型的List 的数据。我假设您已经有一些东西可以获取ResultSet，对其进行迭代并将.add 添加到DbStudent 对象列表中。
类似：
public List<DbStudent> getStudents() throws ClassNotFoundException, SQLException {
List<DbStudent> entries = new ArrayList<DbStudent>();
Class.forName(databaseDriver);
this.connection = DriverManager.getConnection(connectionString);
Statement sttm = this.connection.createStatement();
ResultSet rs = sttm.executeQuery("select * from TMP_STUDENT"); //in your case procedure call
if (rs != null) {
while (rs.next()) { //add the results into the list
entries.add(new DbStudent(rs.getString("FIRSTNAME"), rs.getString("LASTNAME"), rs.getInt("ID"),
rs.getString("SUB"), rs.getString("PERCENT")));
}
rs.close();
}
return entries;
}
现在，主要方法。它包含从数据库对象列表中提取所有信息的逻辑。基本上我们按 id 对其进行排序，遍历它检查是否找到新学生。如果我们找到一个新学生，我们会将前一个学生添加到 Student 对象列表中。该学生已经设置了分数。
public static void main(String[] args) throws JAXBException {
//get the data from the database as is
OracleConnection myOracleConnection = new OracleConnection(ORACLE_DRIVER, ORACLE_CONN);
List<DbStudent> dbStudentList = null;
try {
dbStudentList = myOracleConnection.getStudents(); //get the list of students from the procedure or query
myOracleConnection.CloseConnection();
} catch (ClassNotFoundException e) {
e.printStackTrace();
System.out.println("Stopping execution and exiting...");
System.exit(-1);
} catch (SQLException e) {
e.printStackTrace();
System.out.println("Stopping execution and exiting...");
System.exit(-1);
}
//sort the list on Id, so we can know when we find a new student
Collections.sort(dbStudentList, new Comparator<DbStudent>() {
public int compare(DbStudent s1, DbStudent s2) {
return s1.getId().compareTo(s2.getId());
}
});
List<Student> studentList=new ArrayList<Student>(); //list which will hold all the student objects
Integer previousId = 0; //control variable
List<ScoreRecord> marksList = new ArrayList<ScoreRecord>(); //list to store the marks for each student
Student s = null;
for (int i=0;i<dbStudentList.size();i++) {
if(i==dbStudentList.size()-1){ //if we reached the end, no more students after this record, set the marks and add the student to the list
s.setScoreRecords(marksList);
studentList.add(s);
}
if (dbStudentList.get(i).getId().compareTo(previousId) != 0) {
//new student found
if(s!=null){
//if new student found add the previous one to the list after setting the marks
s.setScoreRecords(marksList);
studentList.add(s);
}
s = new Student(); //create a new student
s.setFirstName(dbStudentList.get(i).getFirstName());
s.setId(dbStudentList.get(i).getId());
s.setLastName(dbStudentList.get(i).getLastName());
ScoreRecord sr = new ScoreRecord();
sr.setSub(dbStudentList.get(i).getSub());
sr.setPercent(dbStudentList.get(i).getPercent());
marksList = new ArrayList<ScoreRecord>(); //reset marks list
marksList.add(sr);
} else {
//same student
ScoreRecord sr = new ScoreRecord();
sr.setSub(dbStudentList.get(i).getSub());
sr.setPercent(dbStudentList.get(i).getPercent());
marksList.add(sr); //add mark to existing marks list
}
previousId=dbStudentList.get(i).getId(); //set the control variable to the new id
}
StudentGroup sg=new StudentGroup(); //create the student wrapper
sg.setStudents(studentList); //add the student list to the wrapper
//create xml with JAXB
JAXBContext context = JAXBContext.newInstance(StudentGroup.class);
Marshaller m = context.createMarshaller();
m.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
m.marshal(sg, new File(STUDENT_XML));
}
xml 的输出正是您想要的：
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Records>
<StudentRecord>
<FirstName>AA1</FirstName>
<LastName>BB1</LastName>
<Id>1</Id>
<MarksList>
<Mark>
<sub>Math</sub>
<percent>51%</percent>
</Mark>
<Mark>
<sub>Phy</sub>
<percent>61%</percent>
</Mark>
<Mark>
<sub>Bio</sub>
<percent>61%</percent>
</Mark>
</MarksList>
</StudentRecord>
<StudentRecord>
<FirstName>AA2</FirstName>
<LastName>BB2</LastName>
<Id>2</Id>
<MarksList>
<Mark>
<sub>Bio</sub>
<percent>62%</percent>
</Mark>
</MarksList>
</StudentRecord>
<StudentRecord>
<FirstName>AA3</FirstName>
<LastName>BB3</LastName>
<Id>3</Id>
<MarksList>
<Mark>
<sub>Math</sub>
<percent>53%</percent>
</Mark>
<Mark>
<sub>Phy</sub>
<percent>63%</percent>
</Mark>
<Mark>
<sub>Chem</sub>
<percent>63%</percent>
</Mark>
</MarksList>
</StudentRecord>
</Records>