數據流:DataOutputStream與DataInputStream的使用

看這兩個類的名字就不難猜想出它們的類關係圖。

DataOutputStream： 主要是一些writeXxx()操做，寫出， 至關於序列化

DataInputStream： 主要是一些readXxx()操做，寫入， 至關於反序列化

通常狀況下，二者會成對出現。 在使用過程當中要特別注意， 一個writeXxx() 對應着一個readXxx(), 千萬不要用readInt()去對應writeBoolean().

說白了，就是序列化與反序列化要匹配。

下面舉個例子，將Student對象的屬性序列化後保存到文件中，而後反序列還原，示例代碼以下：

 

public class Student {
    private int id;
    private String name;
    private long age;
    private boolean gender;

    public Student(int id, String name, long age, boolean gender) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.gender = gender;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public long getAge() {
        return age;
    }

    public void setAge(long age) {
        this.age = age;
    }

    public boolean isGender() {
        return gender;
    }

    public void setGender(boolean gender) {
        this.gender = gender;
    }

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                ", gender=" + gender +
                '}';
    }
}

 

 

 

 @Test
    public void testDataStream() throws IOException {
        // 建立一個Student對象
        Student student = new Student(1, "鄭欽鋒", 100, true);
        // 建立一個DataOutputStream對象
        OutputStream outputStream = new FileOutputStream("E:\\360downloads\\wpcache\\srvsetwp\\student.txt");
        DataOutputStream dataOutputStream = new DataOutputStream(outputStream);
        // 對java的8種基本數據類型進行write操做，其實就至關於序列化操做
        dataOutputStream.writeInt(student.getId());
        dataOutputStream.writeUTF(student.getName());
        dataOutputStream.writeLong(student.getAge());
        dataOutputStream.writeBoolean(student.isGender());
        // 關流
        dataOutputStream.close();


        // 讀取文件，進行反序列化操做
        FileInputStream inputStream = new FileInputStream("E:\\360downloads\\wpcache\\srvsetwp\\student.txt");
        DataInputStream dataInputStream = new DataInputStream(inputStream);
        int id = dataInputStream.readInt();
        String name = dataInputStream.readUTF();
        long age = dataInputStream.readLong();
        boolean gender = dataInputStream.readBoolean();

        // 還原這個student對象
        Student retStudent = new Student(id, name, age, gender);
        System.out.println(retStudent);  // Student{id=1, name='鄭欽鋒', age=100, gender=true}
        dataInputStream.close();
    }
}

 

若是序列化與反序列化不匹配，就是個悲劇，請看下面的示例：

  @Test
    public void testDataStream() throws IOException {
        // 建立一個Student對象
        Student student = new Student(1, "鄭欽鋒", 100, true);
        // 建立一個DataOutputStream對象
        OutputStream outputStream = new FileOutputStream("E:\\360downloads\\wpcache\\srvsetwp\\student.txt");
        DataOutputStream dataOutputStream = new DataOutputStream(outputStream);
        // 對java的8種基本數據類型進行write操做，其實就至關於序列化操做
        dataOutputStream.writeLong(student.getAge());
        dataOutputStream.writeBoolean(student.isGender());
        dataOutputStream.writeUTF(student.getName());
        dataOutputStream.writeInt(student.getId());
        // 關流
        dataOutputStream.close();


        // 讀取文件，進行反序列化操做
        FileInputStream inputStream = new FileInputStream("E:\\360downloads\\wpcache\\srvsetwp\\student.txt");
        DataInputStream dataInputStream = new DataInputStream(inputStream);
        int id = dataInputStream.readInt();
        String name = dataInputStream.readUTF();
        long age = dataInputStream.readLong();
        boolean gender = dataInputStream.readBoolean();

        // 還原這個student對象
        Student retStudent = new Student(id, name, age, gender);
        System.out.println(retStudent); // Student{id=0, name='', age=28148597348991889, gender=true}
        dataInputStream.close();
    }

 

因此，write序列化的順序是： int(id) ---> string(name) ---> long(age)----> boolean(gender);

read反序列化的順序必定要是： int(id) ---> string(name) ---> long(age)----> boolean(gender);