尝试在Spring MVC中访问宁静的Web服务时输出无限

Question

i am using spring DAO and spring mvc in my project, once i try to access below url i'm getting huge no of json and that won't stop untill i stop the program.i cant figure this out can some one explain what's happening here.

url :- //http://localhost:8080/plans/11/more

//controller 

    @ResponseBody
    @RequestMapping(value="plans/{pid}/more",method=RequestMethod.GET)
    public Travel showMore(@PathVariable int pid ){
        Travel travel = travelRep.findOne(pid);
        return travel;
    }

model class

public class Travel implements Serializable {

    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)

    private Integer idtravel;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "idtravel")
    private Set<Travellocation> travellocationSet;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "idtravel")
    private Set<Transactions> transactionsSet;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "idtravel")
    private Set<Travelmode> travelmodeSet;
}

//assume that there are getters and setters for the properties in the model class.

Answer 1

travellocationSet and idLocation seem to have a reference to eachother. Spring will go through all the getters so something like this will happen:

idLocation = travellocationSet->getIdLocation();
travellocationSet = idLocation->getTravellocationSet();
idLocation = travellocationSet->getIdLocation();
travellocationSet = idLocation->getTravellocationSet();
// This will continue forever

A solution can be to use the Data Transfer Object pattern. Basically you would copy your data to a new object, which can be used for your viewing part.

Answer 2

Stream content into a separate file (Dump File) Can you try streaming the data into a file provided you have enough memory to understand how huge the data you are going to download

Basically you have to go ahead and create a dump file, parse through the dump file and filter out the necessary data.

I wouldn't advise on DTO pattern as you are not sure how large the size is and moreover if it exceeds the heap size you would receive OOM Exception.

I suggest to go through the link https://www.airpair.com/java/posts/spring-streams-memory-efficiency