JSONPath 表达式以根据条件从数组中获取值或仅获取第一个值
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JSONPath expression to get a value from an array on condition or just the first value
提问by jhericks
Given JSON structured like this:
鉴于 JSON 结构如下：
{
"name":"Some Guy",
"emails":[
{
"description":"primary",
"status":"UNVERIFIED",
"email":"[email protected]"
},
{
"description":"home",
"status":"VERIFIED",
"email":"[email protected]"
},
{
"description":"away",
"status":"VERIFIED",
"email":"[email protected]"
}
]
}
I would like a JSONPath expressionto get the firstemail with status VERIFIEDand if there are none, then just get the first email in the array. So, given the example above, the result would be [email protected]. Given this example:
我想要一个JSONPath 表达式来获取第一封带有状态的电子邮件，VERIFIED如果没有，那么只获取数组中的第一封电子邮件。因此，鉴于上面的示例，结果将是[email protected]。鉴于这个例子：
{
"name":"Some Guy",
"emails":[
{
"description":"primary",
"status":"UNVERIFIED",
"email":"[email protected]"
},
{
"description":"home",
"status":"UNVERIFIED",
"email":"[email protected]"
}
]
}
the result would be [email protected].
Is this possible with a JSONPath expression?
这可以用 JSONPath 表达式实现吗？
回答by approxiblue
You effectively have 2 JSONPath expressions, where the second one (first email) should be evaluated only if the first one (first verified email) returns nothing, so I don't think you can evaluate them both at the same time, in a single expression.
您实际上有 2 个 JSONPath 表达式，其中第二个（第一封电子邮件）仅在第一个（第一个经过验证的电子邮件）不返回任何内容时才应进行评估，因此我认为您不能同时对它们进行一次评估表达。
You can apply them one after the other, though:
不过，您可以一个接一个地应用它们：
public static String getEmail(String json) {
Configuration cf = Configuration.builder().options(Option.SUPPRESS_EXCEPTIONS).build();
DocumentContext ctx = JsonPath.using(cf).parse(json);
List<String> emails = ctx.read("$.emails[?(@.status == 'VERIFIED')].email");
if (!emails.isEmpty()) {
return emails.get(0);
}
return ctx.read("$.emails[0].email");
}
If the email array is empty, ctx.read("$.emails[0].email")will return null instead of throwing an exception, thanks to the optionSUPPRESS_EXCEPTIONS.
如果 email 数组为空，ctx.read("$.emails[0].email")将返回 null 而不是抛出异常，这要归功于optionSUPPRESS_EXCEPTIONS。
If you don't know the number of paths in advance:
如果您事先不知道路径数：
public static String getEmail(String json, String[] paths) {
Configuration cf = Configuration.builder().options(Option.ALWAYS_RETURN_LIST, Option.SUPPRESS_EXCEPTIONS).build();
DocumentContext ctx = JsonPath.using(cf).parse(json);
for (String path : paths) {
List<String> emails = ctx.read(path);
if (!emails.isEmpty()) {
return emails.get(0);
}
}
return null;
}
The optionALWAYS_RETURN_LISTmeans the return type is a list, even when you have one or zero results.
该选项ALWAYS_RETURN_LIST意味着返回类型是一个列表，即使您有一个或零个结果。
回答by jhericks
This code should work perfectly for you
此代码应该非常适合您
//Use the json parsing library to extract the data
JsonPath jp = new JsonPath(json);
Map<String, Object> location = jp.get("name.emails[0]");
System.out.println(location);
