六、BDB JE中對自定義對象的存儲

 使用tuple binding 來綁定自定義數據的步驟

1、 實例化你要存儲的對象
2、 通過com.sleepycat.bind.tuple.TupleBinding class來創建一個tuple binding。
3、 創建一個database，跟序列化的對象不同，你只需要創建一個。
4、 通過繼承第二步的類來創建一個entry binding 對象。
5、 存儲和使用數據

 

自定義對象:
public class Student {

 private int id;
 private String name;
 private int age;

//get()和set()方法

........
}

創建Tuple binding對象:

 

public class StudentTupleBinging extends TupleBinding{

 @Override
 public Object entryToObject(TupleInput input) {
  int id=input.readInt();
  String name=input.readString();
  int age=input.readInt();
  Student student=new Student();
  student.setId(id);
  student.setName(name);
  student.setAge(age);
  return student;
 }

 @Override
 public void objectToEntry(Object object, TupleOutput output) {
  Student student=(Student)object;
  output.writeInt(student.getId());
  output.writeString(student.getName());
  output.writeInt(student.getAge());
 }

}

存儲:

public class StudentMainTwo {

 private Environment myenv;
 private Database mydb;
 private TupleBinding studentBinding;

//d://workspace//MyTest//src//test//student.txt中的文件內容爲

/**
 * 1#Ashley#21
*2#bill#20
*3#skey#19
*4#Jessica#21
*5#Amanda#22
*6#Sarah#20
*7#Brittany#18
*

*/
 private static File studentFile = new File("D://workspace//MyTest//src//test//student.txt");
 private static DatabaseEntry theKey = new DatabaseEntry();
 private static DatabaseEntry theData = new DatabaseEntry();
 public static void main(String[] args) {
  StudentMainTwo studentMainTwo=new StudentMainTwo();
  studentMainTwo.start("D://bdb", 100000, "student");
  try {
   studentMainTwo.loadData();
   studentMainTwo.showStudent();
  } catch (Exception e) {
   e.printStackTrace();
  }
 }

 public void showStudent() throws DatabaseException {
  Cursor cursor = mydb.openCursor(null, null);
  try {
   while (cursor.getNext(theKey, theData, LockMode.DEFAULT) == OperationStatus.SUCCESS) {
    Student stu1 = (Student) studentBinding.entryToObject(theData);
    System.out.println(stu1.getId() + "   " + stu1.getName()
      + "   " + stu1.getAge());
   }
  } catch (Exception e) {
   System.err.println("Error on inventory cursor:");
   System.err.println(e.toString());
   e.printStackTrace();
  } finally {
   cursor.close();
  }
 }

 public void loadData() throws DatabaseException {
  List<String[]> students = loadFile(studentFile, 8);
  studentBinding = new StudentTupleBinging();
  //System.out.println(myenv.getConfig());
  //Transaction txn = myenv.beginTransaction(null, null);
  for (int i = 0; i < students.size(); i++) {
   String[] student = students.get(i);
   try {
    theKey = new DatabaseEntry(student[0].getBytes("utf-8"));
    Student stu = new Student();
    stu.setId(Integer.parseInt(student[0]));
    stu.setName(student[1]);
    stu.setAge(Integer.parseInt(student[2]));
    studentBinding.objectToEntry(stu, theData);
    mydb.put(null, theKey, theData);
   } catch (UnsupportedEncodingException e) {
    e.printStackTrace();
   }
  }
 }

 public void start(String filename, long cacheSize, String dbname) {
  EnvironmentConfig envconfig = new EnvironmentConfig();
  envconfig.setAllowCreate(true);
  envconfig.setReadOnly(false);
  DatabaseConfig dbconfig = new DatabaseConfig();
  dbconfig.setAllowCreate(true);
  dbconfig.setReadOnly(false);
  try {
   myenv = new Environment(new File(filename), envconfig);
   mydb = myenv.openDatabase(null, dbname, dbconfig);
  } catch (Exception e) {
   e.printStackTrace();
  }
 }

 private List<String[]> loadFile(File theFile, int numFields) {
  List<String[]> records = new ArrayList<String[]>();
  try {
   String theLine = null;
   FileInputStream fis = new FileInputStream(theFile);
   BufferedReader br = new BufferedReader(new InputStreamReader(fis));
   while ((theLine = br.readLine()) != null) {
    String[] theLineArray = theLine.split("#");
    if (theLineArray.length != numFields) {
     System.out.println("Malformed line found in "
       + theFile.getPath());
     System.out.println("Line was: '" + theLine);
     System.out.println("length found was: "
       + theLineArray.length);
     //System.exit(-1);
    }
    records.add(theLineArray);
   }
   // Close the input stream handle
   fis.close();
  } catch (FileNotFoundException e) {
   System.err.println(theFile.getPath() + " does not exist.");
   e.printStackTrace();
   usage();
  } catch (IOException e) {
   System.err.println("IO Exception: " + e.toString());
   e.printStackTrace();
   System.exit(-1);
  }
  return records;
 }

 private static void usage() {
  System.out.println("ExampleDatabasePut [-h <env directory>]");
  System.out.println("      [-s <selections file>] [-v <vendors file>]");
  System.exit(-1);
 }

}