foodev.jsondiff

Class JsonDiff

java.lang.Object

foodev.jsondiff.JsonDiff

Direct Known Subclasses:

GsonDiff, Jackson2Diff, JacksonDiff

public class JsonDiff
extends Object

Util for comparing two json-objects and create a new object with a set of instructions to transform the first to the second.

Syntax for instructions:

 
 {
   "key":     "replaced",           // added or replacing key
   "~key":    "replaced",           // added or replacing key (~ doesn't matter for primitive data types)
   "key":     null,                 // added or replacing key with null.
   "~key":    null,                 // added or replacing key with null (~ doesn't matter for null)
   "-key":    0                     // key removed (value is ignored)
   "key":     { "sub": "replaced" } // whole object "key" replaced
   "~key":    { "sub": "merged" }   // key "sub" merged into object "key", rest of object untouched
   "key":     [ "replaced" ]        // whole array added/replaced
   "~key":    [ "replaced" ]        // whole array added/replaced (~ doesn't matter for whole array)
   "key[4]":  { "sub": "replaced" } // object replacing element 4, rest of array untouched
   "~key[4]": { "sub": "merged"}    // merging object at element 4, rest of array untouched
   "key[+4]": { "sub": "array add"} // object inserted after 3 becoming the new 4 (current 4 pushed right)
   "~key[+4]":{ "sub": "array add"} // object inserted after 3 becoming the new 4 (current 4 pushed right)
   "-key[4]:  0                     // removing element 4 current 5 becoming new 4 (value is ignored)
 }
 
 

Instruction order is merge, set, insert, delete. This is important when altering arrays, since insertions will affect the array index of subsequent delete instructions.

When diffing, the object is expanded to a structure like this: Example: {a:[{b:1,c:2},{d:3}]} Becomes a list of:

1. Leaf: obj
2. Leaf: array 0
3. Leaf: obj
4. Leaf: b: 1
5. Leaf: c: 2
6. Leaf: array 1
7. Leaf: obj
8. Leaf: d: 3

Author:

Martin Algesten

Field Summary

Fields

Modifier and Type	Field and Description
protected Wrapper	factory

Method Summary

Modifier and Type	Method and Description
void	apply(Object orig, Object patch) Patches the first argument with the second.
String	apply(String orig, String patch) Modifies the given original JSON object using the instructions provided and returns the result.
Object	diff(Object from, Object to) Runs a diff using underlying JSON parser implementations.
String	diff(String from, String to) Runs a diff on the two given JSON objects given as string to produce another JSON object with instructions of how to transform the first argument to the second.
Visitor<?>	getVisitor()
void	setVisitor(Visitor<?> visitor) Registers a new visitor.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

factory

protected final Wrapper factory

Method Detail

apply

public void apply(Object orig,
                  Object patch)

Patches the first argument with the second. Accepts two GSON JsonObject or (if jar is provided) a Jackson style ObjectNode.

Parameters:

orig - Object to patch. One of JsonObject or ObjectNode (if jar available).

patch - Object holding patch instructions. One of JsonObject or ObjectNode (if jar available).

Throws:

IllegalArgumentException - if the given arguments are not accepted.

apply

public String apply(String orig,
                    String patch)
             throws IllegalArgumentException

Modifies the given original JSON object using the instructions provided and returns the result. Each argument is expected to be a JSON object {}.

Parameters:

orig - The original JSON object to modify.

patch - The set of instructions to use.

Returns:

The modified JSON object.

Throws:

IllegalArgumentException - if the given arguments are not accepted.

diff

public Object diff(Object from,
                   Object to)
            throws IllegalArgumentException

Runs a diff using underlying JSON parser implementations. Accepts two GSON JsonObject or (if jar is provided) a Jackson style ObjectNode. The returned type is the same as the received.

Parameters:

from - Object to transform from. One of JsonObject or ObjectNode (if jar available).

to - Object to transform to. One of JsonObject or ObjectNode (if jar available).

Returns:

Object containing the instructions. The type will be the same as that passed in constructor.

Throws:

IllegalArgumentException - if the given arguments are not accepted.

diff

public String diff(String from,
                   String to)
            throws IllegalArgumentException

Runs a diff on the two given JSON objects given as string to produce another JSON object with instructions of how to transform the first argument to the second. Both from/to are expected to be objects {}.

Parameters:

from - The origin to transform

to - The desired result

Returns:

The set of instructions to go from to as a JSON object {}.

Throws:

IllegalArgumentException - if the given arguments are not accepted.

getVisitor

public Visitor<?> getVisitor()

Returns:

the registered visitor if any

See Also:

Visitor

setVisitor

public void setVisitor(Visitor<?> visitor)

Registers a new visitor.

Parameters:

visitor - - visitor to register

See Also:

Visitor