如何在不通过ObjectMapper时在JsonParser上设置ObjectCodec? [英] How do you set an ObjectCodec on a JsonParser when not going through an ObjectMapper?
问题描述
注意:这是使用Jackson 2.3.2
Note: this is using Jackson 2.3.2
为了我的一个项目的需要,我正在编写一个自定义 JsonParser
,它记录了一个 Map
,其中键是 JsonPointer
s,值是整数
s(指针指向的行号)。
For the needs of one of my projects, I am writing a custom JsonParser
which records a Map
where keys are JsonPointer
s and values are Integer
s (line numbers where the pointer points to).
该类命名为 LineRecorderJsonParser
。它由 LineRecorderJsonFactory
生成,这是一个简单的委托:
The class is named LineRecorderJsonParser
. It is produced by a LineRecorderJsonFactory
which is a simple delegate:
public final class LineRecorderJsonFactory
extends JsonFactory
{
@Override
protected JsonParser _createParser(final InputStream in,
final IOContext ctxt)
throws IOException, JsonParseException
{
final JsonParser parser = super._createParser(in, ctxt);
return new LineRecorderJsonParser(parser);
}
@Override
protected JsonParser _createParser(final Reader r, final IOContext ctxt)
throws IOException, JsonParseException
{
final JsonParser parser = super._createParser(r, ctxt);
return new LineRecorderJsonParser(parser);
}
@Override
protected JsonParser _createParser(final byte[] data, final int offset,
final int len, final IOContext ctxt)
throws IOException, JsonParseException
{
final JsonParser parser = super._createParser(data, offset, len, ctxt);
return new LineRecorderJsonParser(parser);
}
}
我已经使用以下代码测试了代码的工作原理:
I have tested that the code works using the following code:
public static void main(final String... args)
throws IOException
{
final JsonFactory factory = new LineRecorderJsonFactory();
final ObjectMapper mapper = new ObjectMapper(factory);
final Closer closer = Closer.create();
final InputStream in;
try {
in = closer.register(LineTesting.class.getResourceAsStream
("/testfile.json"));
mapper.readTree(in);
} finally {
closer.close();
}
}
但现在我想测试它;所以我编写了以下测试代码:
But now I want to test it; so I wrote the following test code:
public final class LineRecorderJsonParserTest
{
private static final String INCORRECT_LINE_INFO
= "generated line info is incorrect; expected: %s, actual: %s";
private JsonFactory factory;
private ObjectMapper mapper;
@BeforeMethod
public void initFactory()
{
factory = new LineRecorderJsonFactory();
mapper = new ObjectMapper();
}
@DataProvider
public Iterator<Object[]> getLineData()
{
final List<Object[]> list = Lists.newArrayList();
list.add(new Object[] { "1" });
return list.iterator();
}
@Test(dataProvider = "getLineData")
public void lineNumbersAreCorrectlyReported(final String subdir)
throws IOException
{
final String basePath = "/parser/" + subdir + '/';
final Closer closer = Closer.create();
final TypeReference<Map<JsonPointer, Integer>> typeRef
= new TypeReference<Map<JsonPointer, Integer>>() {};
final InputStream input, lines;
final Map<JsonPointer, Integer> actual, expected;
final LineRecorderJsonParser parser;
try {
input = closer.register(inputFrom(basePath + "input.json"));
lines = closer.register(inputFrom(basePath + "lines.json"));
expected = mapper.readValue(lines, typeRef);
parser = (LineRecorderJsonParser) factory.createParser(input);
//parser.setCodec(factory.getCodec()); // Doesn't change anything...
parser.readValueAsTree(); // FAILS HERE
actual = parser.getLineInfo();
assertEquals(actual, expected,
String.format(INCORRECT_LINE_INFO, expected, actual));
} catch (IOException e) {
throw closer.rethrow(e);
} finally {
closer.close();
}
}
private static InputStream inputFrom(final String path)
{
return LineRecorderJsonParserTest.class.getResourceAsStream(path);
}
}
不幸的是,这不起作用。我得到以下异常:
Unfortunately this doesn't work. I get the following exception:
java.lang.IllegalStateException: No ObjectCodec defined for the parser, can not deserialize JSON into JsonNode tree
at com.fasterxml.jackson.core.JsonParser.readValueAsTree(JsonParser.java:1507)
at com.fasterxml.jackson.core.util.JsonParserDelegate.readValueAsTree(JsonParserDelegate.java:371)
at com.github.fge.jackson.parse.LineRecorderJsonParserTest.lineNumbersAreCorrectlyReported(LineRecorderJsonParserTest.java:84)
即使我(尝试并且)设置了一个 ObjectCodec
我自己(见代码),我也得到这个例外......
Even when I (try and) set an ObjectCodec
myself (see code), I get this exception...
我做错了什么?我如何测试这个类,因为当你直接使用 ObjectMapper
读取时,你没有机会获取底层解析器?
What am I doing wrong? How can I test this class, since when you read using an ObjectMapper
directly, you don't get a chance to grab the underlying parser?
推荐答案
或者, JsonFactory.setCodec(mapper)
。
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