ObjectMapper doesn't fail on trailing characters

I'm having the following class:

public class Car{
private String id;
private String name;

public Car() {
}

public Car(String id, String name) {
    this.id = id;
    this.name = name;
}

public String getId() {
    return id;
}

public void setId(String id) {
    this.id = id;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

}

and I use it like this:

String json = "{\"id\":\"1\", \"name\":\"hh\"} {\"id\":\"2\", \"name\":\"ccc\"}";

    Car car;
    try {
        ObjectMapper mapper = new ObjectMapper();
        car = mapper.readValue(json, new TypeReference<Car>() {
        });
    } catch (IOException e) {
        car = null;
    }

I'm expecting it to fail but instead, I get the first object in the input, the "first" car object.

why is that happening?

You need to enable FAIL_ON_TRAILING_TOKENS feature to throw an exception in this case:

ObjectMapper mapper = new ObjectMapper();
mapper.enable(DeserializationFeature.FAIL_ON_TRAILING_TOKENS);

or since version 2.10:

ObjectMapper mapper = JsonMapper.builder()
		.enable(DeserializationFeature.FAIL_ON_TRAILING_TOKENS)
		.build();

From documentation:

> Feature that determines behaviour for data-binding after binding the
> root value. If feature is enabled, one more call to
> JsonParser.nextToken() is made to ensure that no more tokens are found
> (and if any is found, MismatchedInputException is thrown); if
> disabled, no further checks are made. Feature could alternatively be
> called READ_FULL_STREAM, since it effectively verifies that input
> stream contains only as much data as is needed for binding the full
> value, and nothing more (except for possible ignorable white space or
> comments, if supported by data format).
>
> Feature is disabled by default (so that no check is made for possible
> trailing token(s)) for backwards compatibility reasons.

You can enable all features from FAIL_ON_* family to be as strict as possible.

Alternative.
Note, your type reference is not a Car, but a List of Cars.

final ObjectMapper mapper = new ObjectMapper();
final TypeReference<List<Car>> typeReference = new TypeReference<List<Car>>() {};


final String json = "{\"id\":\"1\", \"name\":\"hh\"} {\"id\":\"2\", \"name\":\"ccc\"}";
List<Car> cars = null;

try {
    cars = mapper.readValue(json, typeReference);
} catch (IOException e) {
    e.printStackTrace();   // TODO - Please, handle it
    cars = null;
}

System.out.println("Cars: " + cars);

It will print:

com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `java.util.ArrayList<com.yk.training.backperssure.Car>` out of START_OBJECT token
 at [Source: (String)"{"id":"1", "name":"hh"} {"id":"2", "name":"ccc"}"; line: 1, column: 1]
	at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:59)
	at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1464)

// More stack trace.,..\

Cars: null