BAEL-5157 - Exception Handling with Jersey (#12045)

First draft:
https://drafts.baeldung.com/wp-admin/post.php?post=131880&action=edit

jersey/src/main/java/com/baeldung/jersey/exceptionhandling/ExceptionHandlingConfig.java

@@ -0,0 +1,19 @@
+package com.baeldung.jersey.exceptionhandling;
+
+import javax.ws.rs.ApplicationPath;
+
+import org.glassfish.jersey.server.ResourceConfig;
+
+import com.baeldung.jersey.exceptionhandling.rest.exceptions.IllegalArgumentExceptionMapper;
+import com.baeldung.jersey.exceptionhandling.rest.exceptions.ServerExceptionMapper;
+
+@ApplicationPath("/exception-handling/*")
+public class ExceptionHandlingConfig extends ResourceConfig {
+
+    public ExceptionHandlingConfig() {
+        packages("com.baeldung.jersey.exceptionhandling.rest");
+        register(IllegalArgumentExceptionMapper.class);
+        register(ServerExceptionMapper.class);
+    }
+
+}

jersey/src/main/java/com/baeldung/jersey/exceptionhandling/data/Stock.java

@@ -0,0 +1,33 @@
+package com.baeldung.jersey.exceptionhandling.data;
+
+import com.baeldung.jersey.exceptionhandling.repo.Identifiable;
+
+public class Stock implements Identifiable {
+    private static final long serialVersionUID = 1L;
+    private String id;
+    private Double price;
+
+    public Stock() {
+    }
+
+    public Stock(String id, Double price) {
+        this.id = id;
+        this.price = price;
+    }
+
+    public String getId() {
+        return id;
+    }
+
+    public void setId(String id) {
+        this.id = id;
+    }
+
+    public Double getPrice() {
+        return price;
+    }
+
+    public void setPrice(Double price) {
+        this.price = price;
+    }
+}

jersey/src/main/java/com/baeldung/jersey/exceptionhandling/data/Wallet.java

@@ -0,0 +1,51 @@
+package com.baeldung.jersey.exceptionhandling.data;
+
+import com.baeldung.jersey.exceptionhandling.repo.Identifiable;
+
+public class Wallet implements Identifiable {
+    private static final long serialVersionUID = 1L;
+
+    public static final Double MIN_CHARGE = 50.0;
+    public static final String MIN_CHARGE_MSG = "minimum charge is: " + MIN_CHARGE;
+
+    private String id;
+    private Double balance = 0.0;
+
+    public Wallet() {
+    }
+
+    public Wallet(String id) {
+        this.id = id;
+    }
+
+    public String getId() {
+        return id;
+    }
+
+    public void setId(String id) {
+        this.id = id;
+    }
+
+    public Double getBalance() {
+        return balance;
+    }
+
+    public void setBalance(Double balance) {
+        this.balance = balance;
+    }
+
+    public Double addBalance(Double amount) {
+        if (balance == null)
+            balance = 0.0;
+
+        return balance += amount;
+    }
+
+    public boolean hasFunds(Double amount) {
+        if (balance == null || amount == null) {
+            return false;
+        }
+
+        return (balance - amount) >= 0;
+    }
+}

jersey/src/main/java/com/baeldung/jersey/exceptionhandling/repo/Db.java

@@ -0,0 +1,32 @@
+package com.baeldung.jersey.exceptionhandling.repo;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Optional;
+import java.util.UUID;
+
+public class Db<T extends Identifiable> {
+    private Map<String, T> db = new HashMap<>();
+
+    public Optional<T> findById(String id) {
+        return Optional.ofNullable(db.get(id));
+    }
+
+    public String save(T t) {
+        String id = t.getId();
+        if (id == null) {
+            id = UUID.randomUUID()
+                .toString();
+            t.setId(id);
+        }
+        db.put(id, t);
+        return id;
+    }
+
+    public void remove(T t) {
+        db.entrySet()
+            .removeIf(entry -> entry.getValue()
+                .getId()
+                .equals(t.getId()));
+    }
+}

jersey/src/main/java/com/baeldung/jersey/exceptionhandling/repo/Identifiable.java

@@ -0,0 +1,17 @@
+package com.baeldung.jersey.exceptionhandling.repo;
+
+import java.io.Serializable;
+
+public interface Identifiable extends Serializable {
+    void setId(String id);
+
+    String getId();
+
+    public static void assertValid(Identifiable i) {
+        if (i == null)
+            throw new IllegalArgumentException("object cannot be null");
+
+        if (i.getId() == null)
+            throw new IllegalArgumentException("object id cannot be null");
+    }
+}

jersey/src/main/java/com/baeldung/jersey/exceptionhandling/rest/StocksResource.java

@@ -0,0 +1,42 @@
+package com.baeldung.jersey.exceptionhandling.rest;
+
+import java.util.Optional;
+
+import javax.ws.rs.Consumes;
+import javax.ws.rs.GET;
+import javax.ws.rs.POST;
+import javax.ws.rs.Path;
+import javax.ws.rs.PathParam;
+import javax.ws.rs.Produces;
+import javax.ws.rs.core.MediaType;
+import javax.ws.rs.core.Response;
+
+import com.baeldung.jersey.exceptionhandling.data.Stock;
+import com.baeldung.jersey.exceptionhandling.repo.Db;
+import com.baeldung.jersey.exceptionhandling.service.Repository;
+
+@Path("/stocks")
+public class StocksResource {
+    private static final Db<Stock> stocks = Repository.STOCKS_DB;
+
+    @POST
+    @Consumes(MediaType.APPLICATION_JSON)
+    @Produces(MediaType.APPLICATION_JSON)
+    public Response post(Stock stock) {
+        stocks.save(stock);
+
+        return Response.ok(stock)
+            .build();
+    }
+
+    @GET
+    @Path("/{ticker}")
+    @Produces(MediaType.APPLICATION_JSON)
+    public Response get(@PathParam("ticker") String id) {
+        Optional<Stock> stock = stocks.findById(id);
+        stock.orElseThrow(IllegalArgumentException::new);
+
+        return Response.ok(stock.get())
+            .build();
+    }
+}

jersey/src/main/java/com/baeldung/jersey/exceptionhandling/rest/WalletsResource.java

@@ -0,0 +1,98 @@
+package com.baeldung.jersey.exceptionhandling.rest;
+
+import java.util.Optional;
+
+import javax.ws.rs.Consumes;
+import javax.ws.rs.GET;
+import javax.ws.rs.POST;
+import javax.ws.rs.PUT;
+import javax.ws.rs.Path;
+import javax.ws.rs.PathParam;
+import javax.ws.rs.Produces;
+import javax.ws.rs.WebApplicationException;
+import javax.ws.rs.core.MediaType;
+import javax.ws.rs.core.Response;
+import javax.ws.rs.core.Response.Status;
+
+import com.baeldung.jersey.exceptionhandling.data.Stock;
+import com.baeldung.jersey.exceptionhandling.data.Wallet;
+import com.baeldung.jersey.exceptionhandling.repo.Db;
+import com.baeldung.jersey.exceptionhandling.rest.exceptions.InvalidTradeException;
+import com.baeldung.jersey.exceptionhandling.rest.exceptions.RestErrorResponse;
+import com.baeldung.jersey.exceptionhandling.service.Repository;
+
+@Path("/wallets")
+public class WalletsResource {
+    private static final Db<Stock> stocks = Repository.STOCKS_DB;
+    private static final Db<Wallet> wallets = Repository.WALLETS_DB;
+
+    @POST
+    @Consumes(MediaType.APPLICATION_JSON)
+    @Produces(MediaType.APPLICATION_JSON)
+    public Response post(Wallet wallet) {
+        wallets.save(wallet);
+
+        return Response.ok(wallet)
+            .build();
+    }
+
+    @GET
+    @Path("/{id}")
+    @Produces(MediaType.APPLICATION_JSON)
+    public Response get(@PathParam("id") String id) {
+        Optional<Wallet> wallet = wallets.findById(id);
+        wallet.orElseThrow(IllegalArgumentException::new);
+
+        return Response.ok(wallet.get())
+            .build();
+    }
+
+    @PUT
+    @Path("/{id}/{amount}")
+    @Produces(MediaType.APPLICATION_JSON)
+    public Response putAmount(@PathParam("id") String id, @PathParam("amount") Double amount) {
+        Optional<Wallet> wallet = wallets.findById(id);
+        wallet.orElseThrow(IllegalArgumentException::new);
+
+        if (amount < Wallet.MIN_CHARGE) {
+            throw new InvalidTradeException(Wallet.MIN_CHARGE_MSG);
+        }
+        
+        wallet.get()
+            .addBalance(amount);
+        wallets.save(wallet.get());
+
+        return Response.ok(wallet)
+            .build();
+    }
+
+    @POST
+    @Path("/{wallet}/buy/{ticker}")
+    @Produces(MediaType.APPLICATION_JSON)
+    public Response postBuyStock(@PathParam("wallet") String walletId, @PathParam("ticker") String id) {
+        Optional<Stock> stock = stocks.findById(id);
+        stock.orElseThrow(InvalidTradeException::new);
+
+        Optional<Wallet> w = wallets.findById(walletId);
+        w.orElseThrow(InvalidTradeException::new);
+
+        Wallet wallet = w.get();
+        Double price = stock.get()
+            .getPrice();
+
+        if (!wallet.hasFunds(price)) {
+            RestErrorResponse response = new RestErrorResponse();
+            response.setSubject(wallet);
+            response.setMessage("insufficient balance");
+            throw new WebApplicationException(Response.status(Status.NOT_ACCEPTABLE)
+                .entity(response)
+                .build());
+        }
+
+        wallet.addBalance(-price);
+        wallets.save(wallet);
+
+        return Response.ok(wallet)
+            .build();
+    }
+}

jersey/src/main/java/com/baeldung/jersey/exceptionhandling/rest/exceptions/IllegalArgumentExceptionMapper.java

@@ -0,0 +1,23 @@
+package com.baeldung.jersey.exceptionhandling.rest.exceptions;
+
+import javax.ws.rs.core.MediaType;
+import javax.ws.rs.core.Response;
+import javax.ws.rs.ext.ExceptionMapper;
+
+public class IllegalArgumentExceptionMapper implements ExceptionMapper<IllegalArgumentException> {
+    public static final String DEFAULT_MESSAGE = "an illegal argument was provided";
+
+    @Override
+    public Response toResponse(final IllegalArgumentException exception) {
+        return Response.status(Response.Status.EXPECTATION_FAILED)
+            .entity(build(exception.getMessage()))
+            .type(MediaType.APPLICATION_JSON)
+            .build();
+    }
+
+    private RestErrorResponse build(String message) {
+        RestErrorResponse response = new RestErrorResponse();
+        response.setMessage(DEFAULT_MESSAGE + ": " + message);
+        return response;
+    }
+}

jersey/src/main/java/com/baeldung/jersey/exceptionhandling/rest/exceptions/InvalidTradeException.java

@@ -0,0 +1,17 @@
+package com.baeldung.jersey.exceptionhandling.rest.exceptions;
+
+import javax.ws.rs.WebApplicationException;
+import javax.ws.rs.core.Response;
+
+public class InvalidTradeException extends WebApplicationException {
+    private static final long serialVersionUID = 1L;
+    private static final String MESSAGE = "invalid trade operation";
+
+    public InvalidTradeException() {
+        super(MESSAGE, Response.Status.NOT_ACCEPTABLE);
+    }
+
+    public InvalidTradeException(String detail) {
+        super(MESSAGE + ": " + detail, Response.Status.NOT_ACCEPTABLE);
+    }
+}

jersey/src/main/java/com/baeldung/jersey/exceptionhandling/rest/exceptions/RestErrorResponse.java

@@ -0,0 +1,34 @@
+package com.baeldung.jersey.exceptionhandling.rest.exceptions;
+
+public class RestErrorResponse {
+    private Object subject;
+    private String message;
+
+    public RestErrorResponse() {
+    }
+
+    public RestErrorResponse(String message) {
+        this.message = message;
+    }
+
+    public RestErrorResponse(Object subject, String message) {
+        this.subject = subject;
+        this.message = message;
+    }
+
+    public Object getSubject() {
+        return subject;
+    }
+
+    public void setSubject(Object subject) {
+        this.subject = subject;
+    }
+
+    public String getMessage() {
+        return message;
+    }
+
+    public void setMessage(String message) {
+        this.message = message;
+    }
+}

jersey/src/main/java/com/baeldung/jersey/exceptionhandling/rest/exceptions/ServerExceptionMapper.java

@@ -0,0 +1,35 @@
+package com.baeldung.jersey.exceptionhandling.rest.exceptions;
+
+import javax.ws.rs.WebApplicationException;
+import javax.ws.rs.core.MediaType;
+import javax.ws.rs.core.Response;
+import javax.ws.rs.core.Response.Status;
+import javax.ws.rs.ext.ExceptionMapper;
+
+public class ServerExceptionMapper implements ExceptionMapper<WebApplicationException> {
+    public static final String HTTP_405_MESSAGE = "METHOD_NOT_ALLOWED";
+
+    @Override
+    public Response toResponse(final WebApplicationException exception) {
+        String message = exception.getMessage();
+        Response response = exception.getResponse();
+        Status status = response.getStatusInfo()
+            .toEnum();
+
+        switch (status) {
+        case METHOD_NOT_ALLOWED:
+            message = HTTP_405_MESSAGE;
+            break;
+        case INTERNAL_SERVER_ERROR:
+            message = "internal validation - " + exception;
+            break;
+        default:
+            message = "[unhandled response code] " + exception;
+        }
+
+        return Response.status(status)
+            .entity(status + ": " + message)
+            .type(MediaType.TEXT_PLAIN)
+            .build();
+    }
+}

jersey/src/main/java/com/baeldung/jersey/exceptionhandling/service/Repository.java

@@ -0,0 +1,10 @@
+package com.baeldung.jersey.exceptionhandling.service;
+
+import com.baeldung.jersey.exceptionhandling.data.Stock;
+import com.baeldung.jersey.exceptionhandling.data.Wallet;
+import com.baeldung.jersey.exceptionhandling.repo.Db;
+
+public class Repository {
+    public static Db<Stock> STOCKS_DB = new Db<>();
+    public static Db<Wallet> WALLETS_DB = new Db<>();
+}

jersey/src/test/java/com/baeldung/jersey/exceptionhandling/rest/StocksResourceIntegrationTest.java

@@ -0,0 +1,99 @@
+package com.baeldung.jersey.exceptionhandling.rest;
+
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.hamcrest.CoreMatchers.startsWith;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
+
+import java.util.HashMap;
+
+import javax.ws.rs.client.Entity;
+import javax.ws.rs.client.Invocation;
+import javax.ws.rs.core.Application;
+import javax.ws.rs.core.MediaType;
+import javax.ws.rs.core.Response;
+import javax.ws.rs.core.Response.Status;
+
+import org.glassfish.jersey.test.JerseyTest;
+import org.junit.Test;
+
+import com.baeldung.jersey.exceptionhandling.ExceptionHandlingConfig;
+import com.baeldung.jersey.exceptionhandling.data.Stock;
+import com.baeldung.jersey.exceptionhandling.data.Wallet;
+import com.baeldung.jersey.exceptionhandling.rest.exceptions.IllegalArgumentExceptionMapper;
+import com.baeldung.jersey.exceptionhandling.rest.exceptions.RestErrorResponse;
+import com.baeldung.jersey.exceptionhandling.rest.exceptions.ServerExceptionMapper;
+
+public class StocksResourceIntegrationTest extends JerseyTest {
+    private static final Entity<String> EMPTY_BODY = Entity.json("");
+    private static final Stock STOCK = new Stock("BAEL", 51.57);
+    private static final String MY_WALLET = "MY-WALLET";
+    private static final Wallet WALLET = new Wallet(MY_WALLET);
+    private static final int INSUFFICIENT_AMOUNT = (int) (Wallet.MIN_CHARGE - 1);
+
+    @Override
+    protected Application configure() {
+        return new ExceptionHandlingConfig();
+    }
+
+    private Invocation.Builder stocks(String path) {
+        return target("/stocks" + path).request();
+    }
+
+    private Invocation.Builder wallets(String path, Object... args) {
+        return target("/wallets" + String.format(path, args)).request();
+    }
+
+    private Entity<?> entity(Object object) {
+        return Entity.entity(object, MediaType.APPLICATION_JSON_TYPE);
+    }
+
+    @Test
+    public void whenMethodNotAllowed_thenCustomMessage() {
+        Response response = stocks("").get();
+
+        assertEquals(Status.METHOD_NOT_ALLOWED.getStatusCode(), response.getStatus());
+
+        String content = response.readEntity(String.class);
+        assertThat(content, containsString(ServerExceptionMapper.HTTP_405_MESSAGE));
+    }
+
+    @Test
+    public void whenTickerNotExists_thenRestErrorResponse() {
+        Response response = stocks("/UNDEFINED").get();
+
+        assertEquals(Status.EXPECTATION_FAILED.getStatusCode(), response.getStatus());
+
+        RestErrorResponse content = response.readEntity(RestErrorResponse.class);
+        assertThat(content.getMessage(), startsWith(IllegalArgumentExceptionMapper.DEFAULT_MESSAGE));
+    }
+
+    @Test
+    public void givenAmountLessThanMinimum_whenAddingToWallet_thenInvalidTradeException() {
+        wallets("").post(entity(WALLET));
+        Response response = wallets("/%s/%d", MY_WALLET, INSUFFICIENT_AMOUNT).put(EMPTY_BODY);
+
+        assertEquals(Status.NOT_ACCEPTABLE.getStatusCode(), response.getStatus());
+
+        String content = response.readEntity(String.class);
+        assertThat(content, containsString(Wallet.MIN_CHARGE_MSG));
+    }
+
+    @Test
+    public void givenInsifficientFunds_whenBuyingStock_thenWebApplicationException() {
+        stocks("").post(entity(STOCK));
+        wallets("").post(entity(WALLET));
+        
+        Response response = wallets("/%s/buy/%s", MY_WALLET, STOCK.getId()).post(EMPTY_BODY);
+        assertEquals(Status.NOT_ACCEPTABLE.getStatusCode(), response.getStatus());
+
+        RestErrorResponse content = response.readEntity(RestErrorResponse.class);
+        assertNotNull(content.getSubject());
+
+        HashMap<?, ?> subject = (HashMap<?, ?>) content.getSubject();
+        assertEquals(subject.get("id"), WALLET.getId());
+        assertTrue(WALLET.getBalance() < Wallet.MIN_CHARGE);
+    }
+}