如何使用Ballerina的log模块无转义字符记录JSON

当使用Ballerina的log模块记录包含JSON的日志时，直接拼接JSON字符串会导致输出中出现转义字符。例如以下代码：

import ballerina/log;

public function main() {
    json jsonObject = {
        "name": "John Doe",
        "age": 30,
        "city": "New York"
    };
    log:printInfo("Hello this is your json object: " + jsonObject.toJsonString());
}

运行后输出的日志会包含转义的双引号：

time = 2023-11-09T15:15:10.935+05:30 level = INFO module = org/test message = "Hello this is your json object: {\"name\":\"John Doe\", \"age\":30, \"city\":\"New York\"}"

方法1：使用结构化日志参数（推荐） #

避免将JSON字符串拼接到日志消息中，而是把JSON对象作为附加参数传递给日志函数。日志系统会自动解析结构化数据，无需转义：

import ballerina/log;

public function main() {
    json jsonObject = {
        "name": "John Doe",
        "age": 30,
        "city": "New York"
    };
    log:printInfo("Hello this is your json object", jsonObject);
}

输出示例：

time = 2023-11-09T15:15:10.935+05:30 level = INFO module = org/test message = "Hello this is your json object" name = "John Doe" age = 30 city = "New York"

方法2：自定义日志布局（嵌入JSON到消息文本） #

如果需要将JSON直接嵌入到日志消息文本中，可通过自定义日志布局取消消息字段的引号包裹，从而避免转义：

1. 创建日志配置文件log_config.toml：

[log]
layout = """time = ${time:yyyy-MM-dd'T'HH:mm:ss.SSSZ} level = ${level} module = ${module} message = ${message}"""

2. 在代码中加载配置并输出日志：

import ballerina/log;

public function main() returns error? {
    check log:loadConfig("log_config.toml");
    
    json jsonObject = {
        "name": "John Doe",
        "age": 30,
        "city": "New York"
    };
    log:printInfo("Hello this is your json object: " + jsonObject.toJsonString());
}

输出示例：

time = 2023-11-09T15:15:10.935+0530 level = INFO module = org/test message = Hello this is your json object: {"name":"John Doe", "age":30, "city":"New York"}

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