public class MovementEventSource implements EventSource {
private int width = 800;
private int height = 600;
private int stepMax = 5;
private int x = 0;
private int y = 0;
private Random random = new Random();
private Logger logger = Logger.getLogger(getClass().getName());
public MovementEventSource(int width, int height, int stepMax) {
this.width = width;
this.height = height;
this.stepMax = stepMax;
this.x = random.nextInt(width);
this.y = random.nextInt(height);
}
@Override
public void onOpen(Emitter emitter) throws IOException {
query(emitter); //开始生成位置信息
}
@Override
public void onResume(Emitter emitter, String lastEventId)
throws IOException {
updatePosition(lastEventId); //更新起始位置
query(emitter); //开始生成位置信息
}
//根据Last-Event-Id来更新起始位置
private void updatePosition(String id) {
if (id != null) {
String[] pos = id.split(",");
if (pos.length > 1) {
int xPos = -1, yPos = -1;
try {
xPos = Integer.parseInt(pos[0], 10);
yPos = Integer.parseInt(pos[1], 10);
} catch (NumberFormatException e) {
}
if (isValidMove(xPos, yPos)) {
x = xPos;
y = yPos;
}
}
}
}
private void query(Emitter emitter) throws IOException {
emitter.comment("Start sending movement information.");
while(true) {
emitter.comment("");
move(); //移动位置
String id = String.format("%s,%s", x, y);
emitter.id(id); //根据位置生成事件标识符
emitter.data(id); //发送位置信息数据
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
logger.log(Level.WARNING, \
"Movement query thread interrupted. Close the connection.", e);
break;
}
}
emitter.close(); //当循环终止时，关闭连接
}
@Override
public void onClose() {
}
//获取下一个合法的移动位置
private void move() {
while (true) {
int[] move = getMove();
int xNext = x + move[0];
int yNext = y + move[1];
if (isValidMove(xNext, yNext)) {
x = xNext;
y = yNext;
break;
}
}
}
//判断当前的移动位置是否合法
private boolean isValidMove(int x, int y) {
return x >= 0 && x <= width && y >=0 && y <= height;
}
//随机生成下一个移动位置
private int[] getMove() {
int[] xDir = new int[] {-1, 0, 1, 0};
int[] yDir = new int[] {0, -1, 0, 1};
int dir = random.nextInt(4);
return new int[] {xDir[dir] * random.nextInt(stepMax), \
yDir[dir] * random.nextInt(stepMax)};
}
}