Question

我有一个Java项目，它当前将一个地图返回给Camel而没有任何嵌套的键，值对，并且Jackson库使用Jackson库将它编组到JSON中。

例如，如果我将以下两个键值放入demoMap：

Map<String,String> demoMap = new TreeMap<String,String>
demoMap.put("key1","5");
demoMap.put("key2","10");

我得到以下JSON：

{"key1":"5","key2":"10"}

但是，现在我的一些键值条目将具有可选的可见性，我需要将其作为嵌套键值放在我的地图中。任何没有可选可见性的键值都将使用默认值。所以，例如，如果我为key1和key2指定了可见性，而不是key3，我希望得到JSON，如下所示：

{"key1":"5",
 "key2":"10",
 "key3":"17",
 "visibility" : { "key1": "a&b&!c", "key2": "a&b", "_default": "a" }
}

如何让Camel使用嵌套键，值对来编组Java对象？我是一个视觉学习者，所以一个简单的例子会有所帮助。

我尝试将Map更改为具有对象的值，即：

Map<String,Object> demoMap = new TreeMap<String,Object>

然后尝试使用http://examples.javacodegeeks.com/core-java/json/jackson/convert-java-map-to-from-json-using-jackson-example/使用http://camel.apache.org/json.html添加一些键的嵌套键值，以供参考，但是我意识到这只是给了我一堆键下的嵌套值，而不是一堆嵌套键，值对

即使我尝试使用grins，我也遇到了一个来自Camel处理器的错误，其中包含java.lang.ClassCastException，声明java.util.ArrayList无法转换为java.lang.String

同样当我尝试在我的demoMap中嵌套Map时，我得到了这个ClassCastException：

3244 [hello.world.request.timer] ERROR org.apache.camel.processor.DefaultErrorHandler  - Failed delivery for exchangeId: e6518e39-89b7-435e-96d9-ce26811ac67e. Exhausted after delivery attempt: 1 caught: java.lang.ClassCastException: java.util.HashMap cannot be cast to java.lang.String

所以我知道不怎么做。： - /

我在{{3}}重新阅读了Camel JSON文档，但在撰写本文时，它没有指定嵌套键值对的示例。

更新：根据汤姆的反馈我创建了两个地图，即

Map<String,String> keyvalues = new TreeMap<String,String>();
Map<String,String> visibility = new TreeMap<String,String>();

这是我的类，我称之为SensorGenerator，它将属性文件加载到Map中：

package sample;

import java.util.Map;
import java.util.Properties;
import java.util.TreeMap;

import org.codehaus.jackson.annotate.JsonAnyGetter;
import org.codehaus.jackson.annotate.JsonProperty;

public class SensorGenerator {

    private Properties sourceProperties;

    // create a map of sensor keyvalues, and a map of sensor visibility
    Map<String,String> keyvalues = new TreeMap<String,String>();
    @JsonProperty
    Map<String,String> visibility = new TreeMap<String,String>();

    @JsonAnyGetter
    public Map<String, String> getKeyvalues() { 

        for (Object key : sourceProperties.keySet()) {

            // Separate out each of the field:datatype:visibility tuples as an entry in the
            // values array
            String[] values = sourceProperties.getProperty((String) key).split(
                    ",");
            // split the key between 'sensor' and the 'number' Ex: sensor1 -> sensor,1
            String[] keyArray = key.toString().split("(?<=([a-zA-Z]++))");
            String keyNumber = keyArray[1]; // grab the number to append for each sensor

            // define string buffer that appends sensor number for each sensor's
            // keys.  Ex: sensor1 would have s1make, s1makeDataType, etc.
            StringBuffer sensorNumberStringBuffer = new StringBuffer();
            sensorNumberStringBuffer.append("s");
            sensorNumberStringBuffer.append(keyNumber);

            // make, its data type, and visibility (with s# prefix)
            StringBuffer makeStringBuffer = new StringBuffer();
            makeStringBuffer.append(sensorNumberStringBuffer);
            makeStringBuffer.append("make");
            StringBuffer makeDataTypeStringBuffer = new StringBuffer();
            makeDataTypeStringBuffer.append(sensorNumberStringBuffer);
            makeDataTypeStringBuffer.append("makeDataType");
            StringBuffer makeVizStringBuffer = new StringBuffer();
            makeVizStringBuffer.append(sensorNumberStringBuffer);
            makeVizStringBuffer.append("makeViz");

            // model, its data type, and visibility (with s# prefix)
            StringBuffer modelStringBuffer = new StringBuffer();
            modelStringBuffer.append(sensorNumberStringBuffer);
            modelStringBuffer.append("model");
            StringBuffer modelDataTypeStringBuffer = new StringBuffer();
            modelDataTypeStringBuffer.append(sensorNumberStringBuffer);
            modelDataTypeStringBuffer.append("modelDataType");
            StringBuffer modelVizStringBuffer = new StringBuffer();
            modelVizStringBuffer.append(sensorNumberStringBuffer);
            modelVizStringBuffer.append("modelViz");

            // serialNumber, its data type, and visibility (with s# prefix)
            StringBuffer serialNumberStringBuffer = new StringBuffer();
            serialNumberStringBuffer.append(sensorNumberStringBuffer);
            serialNumberStringBuffer.append("serialNumber");
            StringBuffer serialNumberDataTypeStringBuffer = new StringBuffer();
            serialNumberDataTypeStringBuffer.append(sensorNumberStringBuffer);
            serialNumberDataTypeStringBuffer.append("serialNumberDataType");
            StringBuffer serialNumberVizStringBuffer = new StringBuffer();
            serialNumberVizStringBuffer.append(sensorNumberStringBuffer);
            serialNumberVizStringBuffer.append("serialNumberViz");

            // sensorType, its data type, and visibility (with s# prefix)
            StringBuffer sensorTypeStringBuffer = new StringBuffer();
            sensorTypeStringBuffer.append(sensorNumberStringBuffer);
            sensorTypeStringBuffer.append("sensorType");
            StringBuffer sensorTypeDataTypeStringBuffer = new StringBuffer();
            sensorTypeDataTypeStringBuffer.append(sensorNumberStringBuffer);
            sensorTypeDataTypeStringBuffer.append("sensorTypeDataType");
            StringBuffer sensorTypeVizStringBuffer = new StringBuffer();
            sensorTypeVizStringBuffer.append(sensorNumberStringBuffer);
            sensorTypeVizStringBuffer.append("sensorTypeViz");

            //  put all the field:datatype keyvalues for this sensor in the keyvalues map
            //  and visibilities in the visibility map

            // make, data type, and visibility
            keyvalues.put(makeStringBuffer.toString(), values[0].split(":")[0]);
            keyvalues.put(makeDataTypeStringBuffer.toString(), values[0].split(":")[1]);
            visibility.put(makeVizStringBuffer.toString(), values[0].split(":")[2]);

            // model, data type, and visibility
            keyvalues.put(modelStringBuffer.toString(), values[1].split(":")[0]);
            keyvalues.put(modelDataTypeStringBuffer.toString(), values[1].split(":")[1]);
            visibility.put(modelVizStringBuffer.toString(), values[1].split(":")[2]);

            // serialNumber, data type, and visibility
            keyvalues.put(serialNumberStringBuffer.toString(), values[2].split(":")[0]);
            keyvalues.put(serialNumberDataTypeStringBuffer.toString(), values[2].split(":")[1]);
            visibility.put(serialNumberVizStringBuffer.toString(), values[2].split(":")[2]);

            // sensorType, data type, and visibility
            keyvalues.put(sensorTypeStringBuffer.toString(), values[3].split(":")[0]);
            keyvalues.put(sensorTypeDataTypeStringBuffer.toString(), values[3].split(":")[1]);
            visibility.put(sensorTypeVizStringBuffer.toString(), values[3].split(":")[2]);

            // add in default visibility
            visibility.put("_default", "a");

        }
        return keyvalues;
    }

    public void setSourceProperties(Properties properties) {
        this.sourceProperties = properties;
    }

}

现在我只是将默认的可见性硬编码为“a”，但稍后会将其更改为从属性文件中提取。

Answer 1

您的结构不仅仅是一张地图。它是两个不同序列化的地图。表示这一点的一种方法是：

public class Whatever{
  Map<String,String> keyvalues;
  Map<String,String> visibility;
}

你最终会得到的是这个，尽管这表示数据远非理想：

{
 "keyvalues" : { "key1": "5", "key2": "10", "key3": "17"},
 "visibility" : { "key1": "a&b&!c", "key2": "a&b", "_default": "a" }
}

要获得所需内容，请使用@JsonAnyGetter。像这样的东西（它可以更容易使用）：

public class Whatever{
    Map<String,String> keyvalues = new TreeMap<String,String>();
    @JsonProperty
    Map<String,String> visibility = new TreeMap<String,String>();

    @JsonAnyGetter
    public Map<String, String> getKeyvalues() {
        return keyvalues;
    }
}

产生：

           {"visibility":{"key1":"a&b&!c","key2":"a&b"},"key1":"5","key2":"10"}

我今天一直在与此作斗争，你的问题激励我做出血腥的工作：D注释在这里：https://github.com/FasterXML/jackson-annotations/wiki/Jackson-Annotations

请参阅此处的JUnit测试：https://gist.github.com/TomDemeranville/7009250

如何使用Camel和Jackson库将嵌套的键值对于JSON编组？

1 个答案: