Logic App中Liquid模板如何将JSON对象映射为字符串输出

问题说明 #

在Logic App的Liquid映射中，尝试将输入的JSON对象作为字符串映射到输出的body字段时，发现body字段为空；使用json过滤器后仍未解决，需要实现将JSON对象序列化为转义后的字符串作为body值的输出格式。

输入示例 #

[ 
  { 
    "firstName": "FirstName1", 
    "lastName": "LastName1" 
  }, 
  { 
    "firstName": "FirstName2", 
    "lastName": "LastName2" 
  }, 
  { 
    "firstName": "FirstName3", 
    "lastName": "LastName3" 
  } 
]

尝试过的Liquid代码 #

[ 
    {%- for rec in content -%} 
        { 
            "BrokerProperties": { 
                "ContentType": "application/json", 
                "SessionId": "1" 
            }, 
            "body": "{{ rec }}" 
        } 
        {% if forloop.last == false %},{% endif %} 
    {%- endfor -%} 
]

期望输出 #

[ 
  { 
    "BrokerProperties": { 
      "ContentType": "application/json", 
      "SessionId": "1" 
    }, 
    "body": "{\"firstName\": \"FirstName1\",\"lastName\": \"LastName1\"}" 
  }, 
  { 
    "BrokerProperties": { 
      "ContentType": "application/json", 
      "SessionId": "1" 
    }, 
    "body": "{\"firstName\": \"FirstName2\",\"lastName\": \"LastName2\"}" 
  }, 
  { 
    "BrokerProperties": { 
      "ContentType": "application/json", 
      "SessionId": "1" 
    }, 
    "body": "{\"firstName\": \"FirstName3\",\"lastName\": \"LastName3\"}" 
  } 
]

解决方案 #

正确的Liquid代码 #

[ 
    {%- for rec in content -%} 
        { 
            "BrokerProperties": { 
                "ContentType": "application/json", 
                "SessionId": "1" 
            }, 
            "body": "{{ rec | json | replace: '"', '\\"' }}" 
        } 
        {% if forloop.last == false %},{% endif %} 
    {%- endfor -%} 
]

代码说明 #

1. rec | json：将单个JSON对象序列化为标准JSON字符串；
2. replace: '"', '\\"'：把JSON字符串中的双引号转义为\"，避免和外层JSON的双引号冲突，确保输出的JSON格式合法；
3. 保留原有的循环和逗号处理逻辑，保证输出是合法的JSON数组。

也可以使用capture捕获JSON字符串后再转义，效果一致：

[ 
    {%- for rec in content -%}
        {% capture rec_json %}{{ rec | json }}{% endcapture %}
        { 
            "BrokerProperties": { 
                "ContentType": "application/json", 
                "SessionId": "1" 
            }, 
            "body": "{{ rec_json | escape }}" 
        } 
        {% if forloop.last == false %},{% endif %} 
    {%- endfor -%} 
]

内容的提问来源于stack exchange，提问作者devguy852401