Java 根据数据库记录（占位符）从动态json对象获取值（实值），并用实值替换占位符

在这段代码中，我需要根据数据库记录从动态json对象中获取值。我在数据库中有两个表，称为notification和Placeholder多对多关系，notification可以包含动态占位符数，一个服务将向该服务发送json post请求，以便用实际值替换占位符，但由于该服务不知道动态占位符数是多少值应该从动态json数组中获取，但json对象包含通知id，使用通知id我可以获取通知对象和相应的占位符，然后我可以从json对象中获取实际值

{  
    "messageId":9,
    "msisdn":"94763703355",
    "<PACKNAME>":"Youtube",
    "<PACKTYPE>":"Social Media",
   
}

下面是动态json对象

{  
    "messageId":9,
    "msisdn":"94763703355",
    "<PACKNAME>":"Youtube",
    "<PACKTYPE>":"Social Media",
   
}

所有占位符都应替换为相关值，但我无法获得预期的输出

@服务 公共类NotificationServiceImpl实现NotificationService{

@Autowired
RestTemplate restTemplate;

@Autowired
NotificationRepository notificationRepository;

@Override
public void getdata(String dynamicJson) throws IOException {


    // create object mapper instance
    ObjectMapper mapper = new ObjectMapper();


    // convert JSON string to Java Object
    DynamicJson dynamicJson1 = mapper.readValue(dynamicJson, DynamicJson.class);

    // print user object
    //System.out.println(dynamicJson1);
    int id = dynamicJson1.getMessageId();

    Optional<Notification> notification = notificationRepository.findById(id);

    List<PlaceHolder> placeHolders = notification.get().getPlaceHolders();


    Map<String, String> replacements = new HashMap<String, String>();
    placeHolders.forEach(i -> replacements.put(i.getValue(), dynamicJson1.getPlaceholders().get(i).toString()));

   String message = notification.get().getMessage();

    StringBuilder result = new StringBuilder(message.length());
    String delimiters = "+-*/(),. ";
    StringTokenizer st = new StringTokenizer(message, delimiters, true);
    while (st.hasMoreTokens()) {
        String w = st.nextToken();
        if (replacements.containsKey(w)) {
            result.append(replacements.get(w));
        } else {
            result.append(w);
        }
    }
    System.out.println(result.toString());


}
}

这就是我得到的输出

You have succuessfully subscribed to Youtube and it will be <PACKTYPE> package

You have succuessfully subscribed to <PACKNAME> and it will be Social Media package

---

占位符和realValue元素计数是动态的，1到n是外部for循环。您可以在占位符上循环。您应该将占位符放在地图中，其值为realValue。类似如下：

Map<String, String> replacements = new HashMap<String, String>();
placeHolders.forEach(i -> replacements.put(i, dynamicJson1.getPlaceholders().get(i).toString()));
            
String sentence = "You have succuessfully subscribe to <PACKNAME> and it will be <PACKTYPE> package";
            
StringBuilder result = new StringBuilder(sentence.length());
String delimiters = "+-*/(),. ";
StringTokenizer st = new StringTokenizer(sentence, delimiters, true);
while (st.hasMoreTokens()) {
   String w = st.nextToken();
   if (replacements.containsKey(w)) {
      result.append(replacements.get(w));
   } else {
      result.append(w);
   }
}
System.out.println(result.toString());

---

这是外部for循环。您在占位符上循环。您应该将占位符放在地图中，其值为realValue。类似如下：

Map<String, String> replacements = new HashMap<String, String>();
placeHolders.forEach(i -> replacements.put(i, dynamicJson1.getPlaceholders().get(i).toString()));
            
String sentence = "You have succuessfully subscribe to <PACKNAME> and it will be <PACKTYPE> package";
            
StringBuilder result = new StringBuilder(sentence.length());
String delimiters = "+-*/(),. ";
StringTokenizer st = new StringTokenizer(sentence, delimiters, true);
while (st.hasMoreTokens()) {
   String w = st.nextToken();
   if (replacements.containsKey(w)) {
      result.append(replacements.get(w));
   } else {
      result.append(w);
   }
}
System.out.println(result.toString());

---

我所做的就是将字符串生成器替换代码部分放在for循环的外面，并使用Hashmap映射占位符和realValue，这样就可以解决这个问题

 @Override
    public void getdata(String dynamicJson) throws IOException {


        // create object mapper instance
        ObjectMapper mapper = new ObjectMapper();


        // convert JSON string to Java Object
        DynamicJson dynamicJson1 = mapper.readValue(dynamicJson, DynamicJson.class);


        int id = dynamicJson1.getMessageId();


        Optional<Notification> notification = notificationRepository.findById(id);

        List<PlaceHolder> placeHolders = notification.get().getPlaceHolders();

        //Changed
        HashMap<String, String> hash_map = new HashMap<String, String>();


        String message = notification.get().getMessage();


        for (int i = 0; i < placeHolders.size(); i++) {


            String placeholder = placeHolders.get(i).getValue();
            String realValue = dynamicJson1.getPlaceholders().get(placeholder).toString();

            //Changed
            hash_map.put(placeholder, realValue);

        }

        //////////////////////////////////////////////////////////////////////////////////

        StringBuilder result = new StringBuilder(message.length());
        String delimiters = "+-*/(),. ";
        StringTokenizer st = new StringTokenizer(message, delimiters, true);
        while (st.hasMoreTokens()) {
            String w = st.nextToken();
            if (hash_map.containsKey(w)) {
                result.append(hash_map.get(w));
            } else {
                result.append(w);
            }
        }


        System.out.println(result.toString());
    }

}

@覆盖
公共void getdata（字符串dynamicJson）引发IOException{
//创建对象映射器实例
ObjectMapper mapper=新的ObjectMapper（）；
//将JSON字符串转换为Java对象
DynamicJson dynamicJson1=mapper.readValue（DynamicJson，DynamicJson.class）；
int id=dynamicJson1.getMessageId（）；
可选通知=notificationRepository.findById（id）；
列表占位符=notification.get（）.getPlaceHolders（）；
//改变
HashMap hash_map=新HashMap（）；
字符串消息=notification.get（）.getMessage（）；
对于（int i=0；i

我可以解决这个问题，我所做的是将字符串生成器替换代码部分放在for循环的外面，并使用Hashmap映射占位符和realValue

 @Override
    public void getdata(String dynamicJson) throws IOException {


        // create object mapper instance
        ObjectMapper mapper = new ObjectMapper();


        // convert JSON string to Java Object
        DynamicJson dynamicJson1 = mapper.readValue(dynamicJson, DynamicJson.class);


        int id = dynamicJson1.getMessageId();


        Optional<Notification> notification = notificationRepository.findById(id);

        List<PlaceHolder> placeHolders = notification.get().getPlaceHolders();

        //Changed
        HashMap<String, String> hash_map = new HashMap<String, String>();


        String message = notification.get().getMessage();


        for (int i = 0; i < placeHolders.size(); i++) {


            String placeholder = placeHolders.get(i).getValue();
            String realValue = dynamicJson1.getPlaceholders().get(placeholder).toString();

            //Changed
            hash_map.put(placeholder, realValue);

        }

        //////////////////////////////////////////////////////////////////////////////////

        StringBuilder result = new StringBuilder(message.length());
        String delimiters = "+-*/(),. ";
        StringTokenizer st = new StringTokenizer(message, delimiters, true);
        while (st.hasMoreTokens()) {
            String w = st.nextToken();
            if (hash_map.containsKey(w)) {
                result.append(hash_map.get(w));
            } else {
                result.append(w);
            }
        }


        System.out.println(result.toString());
    }

}

@覆盖
公共void getdata（字符串dynamicJson）引发IOException{
//创建对象映射器实例
ObjectMapper mapper=新的ObjectMapper（）；
//将JSON字符串转换为Java对象
DynamicJson dynamicJson1=mapper.readValue（DynamicJson，DynamicJson.class）；
int id=dynamicJson1.getMessageId（）；
可选通知=notificationRepository.findById（id）；
列表占位符=notification.get（）.getPlaceHolders（）；
//改变
HashMap hash_map=新HashMap（）；
字符串消息=notification.get（）.getMessage（）；
对于（int i=0；i

您是否尝试过使用调试器单步执行代码？是的，但我无法找出出错的原因。这是您的外部for循环。在占位符上循环。您应该将占位符放在一个映射中，其值为realvalues。您是否尝试过使用调试器单步执行代码？是的，但我无法找出出错的原因。这是您的外部for循环。在占位符上循环。你应该把你的占位符放在一个地图上，值是realvalues，我直接替换了你的核心，因为我对lamda没有太多经验，它要求输入字符串，但提供的类型是占位符替换exception@HashanR，您得到了什么异常？“跟踪”：“java.lang.NullPointerException\r\n\tat com.hashanr.notificationsender.service.NotificationServiceImpl.lambda$getdata$0（NotificationServiceImpl.java:66）\r\n\tat java.lang.Iterable.forEach（Iterable.java:75）\r\n\tat com.hashanr.notificationsender.service.NotificationServiceImpl.getdata（NotificationServiceImpl.java:66）\r\n\t com.hashanr.notificationsender.controller.NotificationController.getObject（NotificationController.java:28）\r\n\t sun.reflect.NativeMethodAccessorImpl.i

Map<String, String> replacements = new HashMap<String, String>();
placeHolders.forEach(i -> replacements.put(i, dynamicJson1.getPlaceholders().get(i).toString()));
            
String sentence = "You have succuessfully subscribe to <PACKNAME> and it will be <PACKTYPE> package";
            
StringBuilder result = new StringBuilder(sentence.length());
String delimiters = "+-*/(),. ";
StringTokenizer st = new StringTokenizer(sentence, delimiters, true);
while (st.hasMoreTokens()) {
   String w = st.nextToken();
   if (replacements.containsKey(w)) {
      result.append(replacements.get(w));
   } else {
      result.append(w);
   }
}
System.out.println(result.toString());

for(String placeHolder: placeHolders) {
    replacements.put(placeHolder, dynamicJson1.getPlaceholders().get(placeHolder).toString()))
}

 @Override
    public void getdata(String dynamicJson) throws IOException {


        // create object mapper instance
        ObjectMapper mapper = new ObjectMapper();


        // convert JSON string to Java Object
        DynamicJson dynamicJson1 = mapper.readValue(dynamicJson, DynamicJson.class);


        int id = dynamicJson1.getMessageId();


        Optional<Notification> notification = notificationRepository.findById(id);

        List<PlaceHolder> placeHolders = notification.get().getPlaceHolders();

        //Changed
        HashMap<String, String> hash_map = new HashMap<String, String>();


        String message = notification.get().getMessage();


        for (int i = 0; i < placeHolders.size(); i++) {


            String placeholder = placeHolders.get(i).getValue();
            String realValue = dynamicJson1.getPlaceholders().get(placeholder).toString();

            //Changed
            hash_map.put(placeholder, realValue);

        }

        //////////////////////////////////////////////////////////////////////////////////

        StringBuilder result = new StringBuilder(message.length());
        String delimiters = "+-*/(),. ";
        StringTokenizer st = new StringTokenizer(message, delimiters, true);
        while (st.hasMoreTokens()) {
            String w = st.nextToken();
            if (hash_map.containsKey(w)) {
                result.append(hash_map.get(w));
            } else {
                result.append(w);
            }
        }


        System.out.println(result.toString());
    }

}