Redux in Java
Using Java and Vavr.
Features
- Store
- Reducer
- CombineReducers
- Middlewares
Install
<dependency>
<groupId>me.grison</groupId>
<artifactId>redux4j</artifactId>
<version>1.0</version>
</dependency>Counter example
public class Counter {
// Actions
static final String INC = "INC";
static final String DEC = "DEC";
// this is our reducer which increments if INC, decrement if DEC
// and does nothing otherwise
final Reducer<String, Integer> reducer =
(action, state) -> state + switch (action) {
case INC -> 1;
case DEC -> -1;
default -> 0;
};
public void foo() {
// This is our store with its initial state of zero and the reducer seen above
Store<Integer, String> store = Redux.createStore(0, reducer);
// dispatch an INC action
store.dispatch(INC);
store.getState(); // 1
// dispatch an DEC action
store.dispatch(DEC);
store.getState(); // 0
}
}Middlewares
public class Counter {
final Middleware<Integer, String> middleware = (store, action, next) -> {
System.out.println("Before " + store.getState());
next.accept(store, action, null);
System.out.println("After " + store.getState());
};
public void foo() {
Store<Integer, String> store = Redux.createStore(0, reducer, middleware);
store.dispatch(INC);
}
}Outputs:
Before 0
After 1
Combine Reducers
public class Foo {
Reducer<String, String> concatBar =
(action, state) -> "CONCAT".equals(action) ? state + "bar" : state;
Reducer<String, Integer> plus2 =
(action, state) -> "PLUS".equals(action) ? state + 2 : state;
Reducer<String, List<String>> addFoo = (action, state) -> {
if ("ADD".equals(action))
state.add("foo");
return state;
};
Reducer reducers = Redux.combineReducers(Tuple.of("str", concatBar), Tuple.of("int", plus2), Tuple.of("list", addFoo));
@Test
public void testCombineReducersMap() {
Map<String, Object> initialState = new HashMap<String, Object>() {{
put("str", "foo");
put("int", 1);
put("list", new ArrayList<String>());
}};
Store<Map<String,Object>, String> store = Redux.createStore(initialState, reducers);
assertThat(store.getState().get("str"), equalTo("foo"));
store.dispatch("CONCAT");
assertThat(store.getState().get("str"), equalTo("foobar"));
assertThat(store.getState().get("int"), equalTo(1));
store.dispatch("PLUS");
assertThat(store.getState().get("int"), equalTo(3));
store.dispatch("PLUS");
assertThat(store.getState().get("int"), equalTo(5));
store.dispatch("CONCAT");
assertThat(store.getState().get("str"), equalTo("foobarbar"));
assertThat(store.getState().get("list"), equalTo(Arrays.asList()));
store.dispatch("ADD");
assertThat(store.getState().get("list"), equalTo(Arrays.asList("foo")));
store.dispatch("ADD");
assertThat(store.getState().get("list"), equalTo(Arrays.asList("foo", "foo")));
}
// same with a javabean with getters/setters
}