ahucoder · ahucoder · Jun 7, 2025 · Jun 7, 2025
diff --git a/src/main/java/chain/App.java b/src/main/java/chain/App.java
@@ -0,0 +1,41 @@
+package chain;
+
+import chain.dto.ApprovalRequestDto;
+import chain.enums.RequestType;
+import chain.handler.ApprovalHandler;
+import chain.processor.CEO;
+import chain.processor.DepartmentManager;
+import chain.processor.HRManager;
+
+public class App {
+    public static void main(String[] args) {
+        // Chain：deptManager -> hrManager -> CEO
+        ApprovalHandler deptManager = new DepartmentManager();
+        ApprovalHandler hrManager = new HRManager();
+        ApprovalHandler ceo = new CEO();
+
+        deptManager.linkWith(hrManager).linkWith(ceo);
+
+        // Different scene requests
+        ApprovalRequestDto r1 = new ApprovalRequestDto(RequestType.LEAVE, "Alice", 0, 2);
+        ApprovalRequestDto r2 = new ApprovalRequestDto(RequestType.EXPENSE, "Bob", 800, 0);
+        ApprovalRequestDto r3 = new ApprovalRequestDto(RequestType.PURCHASE, "Charlie", 5000, 0);
+        ApprovalRequestDto r4 = new ApprovalRequestDto(RequestType.LEAVE, "David", 0, 10);
+
+        System.out.println("--- Start processing requests ---");
+        System.out.printf("--- r1 start [%s]---%n", r1.getType());
+        deptManager.handle(r1);
+        System.out.printf("--- r1 end [%s]---%n", r1.getType());
+        System.out.printf("--- r2 start [%s]---%n", r2.getType());
+        deptManager.handle(r2);
+        System.out.printf("--- r2 end [%s]---%n", r2.getType());
+        System.out.printf("--- r3 start [%s]---%n", r3.getType());
+        deptManager.handle(r3);
+        System.out.printf("--- r3 end [%s]---%n", r3.getType());
+        System.out.printf("--- r4 start [%s]---%n", r4.getType());
+        deptManager.handle(r4);
+        System.out.printf("--- r4 end [%s]---%n", r4.getType());
+
+        System.out.println("--- Request processing completed ---");
+    }
+}
diff --git a/src/main/java/chain/dto/ApprovalRequestDto.java b/src/main/java/chain/dto/ApprovalRequestDto.java
@@ -0,0 +1,14 @@
+package chain.dto;
+
+import chain.enums.RequestType;
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+
+@AllArgsConstructor
+@Getter
+public class ApprovalRequestDto {
+    private final RequestType type;
+    private final String applicant;
+    private final double amount;
+    private final int days;
+}
diff --git a/src/main/java/chain/enums/RequestType.java b/src/main/java/chain/enums/RequestType.java
@@ -0,0 +1,38 @@
+package chain.enums;
+
+public enum RequestType {
+    LEAVE("Leave Application"),
+    EXPENSE("Expense Reimbursement "),
+    PURCHASE("Procurement Request"),
+    ;
+
+    private final String typeName;
+
+    RequestType(String typeName) {
+        this.typeName = typeName;
+    }
+
+    /**
+     * Get a description of the type
+     * @return description of the type
+     */
+    public String getType() {
+        return typeName;
+    }
+
+    /**
+     * Search for the corresponding enumeration value based on the string (case-insensitive)
+     * @param typeStr Type string
+     * @return Corresponding enumeration values
+     * @throws IllegalArgumentException If no matching enumeration value can be found
+     */
+    public static RequestType fromString(String typeStr) {
+        for (RequestType type : values()) {
+            if (type.typeName.equalsIgnoreCase(typeStr)
+                    || type.name().equalsIgnoreCase(typeStr)) {
+                return type;
+            }
+        }
+        throw new IllegalArgumentException("Invalid request type: " + typeStr);
+    }
+}
diff --git a/src/main/java/chain/handler/ApprovalHandler.java b/src/main/java/chain/handler/ApprovalHandler.java
@@ -0,0 +1,41 @@
+package chain.handler;
+
+import chain.dto.ApprovalRequestDto;
+import chain.service.ApprovalRuleService;
+
+import java.util.List;
+
+public abstract class ApprovalHandler {
+    protected ApprovalHandler next;
+    private final List<ApprovalRuleService> rules;
+
+    public ApprovalHandler(List<ApprovalRuleService> rules) {
+        this.rules = rules;
+    }
+
+    //pipeline
+    public ApprovalHandler linkWith(ApprovalHandler next) {
+        this.next = next;
+        return next;
+    }
+
+    public void handle(ApprovalRequestDto request) {
+        if (rules.stream().anyMatch(rule -> rule.evaluate(request))) {
+            System.out.printf("[%s]Approve the %s application for %s: days=%d, amount=%.2f%n",
+                    getClass().getSimpleName(), request.getApplicant(), request.getType(),
+                    request.getDays(), request.getAmount());
+        } else {
+            System.out.printf("[%s]Not in compliance with approval rules, transferred to the next level: %s%n",
+                    getClass().getSimpleName(), next != null ? next.getClass().getSimpleName() : "Null");
+            passToNext(request);
+        }
+    }
+
+    protected void passToNext(ApprovalRequestDto request) {
+        if (next != null) {
+            next.handle(request);
+        } else {
+            System.out.println("[SYSTEM] No one can process this request: " + request.getType());
+        }
+    }
+}
diff --git a/src/main/java/chain/processor/CEO.java b/src/main/java/chain/processor/CEO.java
@@ -0,0 +1,12 @@
+package chain.processor;
+
+import chain.handler.ApprovalHandler;
+import chain.service.impl.DefaultRuleService;
+
+import java.util.List;
+
+public class CEO extends ApprovalHandler {
+    public CEO() {
+        super(List.of(new DefaultRuleService()));
+    }
+}
diff --git a/src/main/java/chain/processor/DepartmentManager.java b/src/main/java/chain/processor/DepartmentManager.java
@@ -0,0 +1,12 @@
+package chain.processor;
+
+import chain.handler.ApprovalHandler;
+import chain.service.impl.LeaveDaysRuleService;
+
+import java.util.List;
+
+public class DepartmentManager extends ApprovalHandler {
+    public DepartmentManager() {
+        super(List.of(new LeaveDaysRuleService(3)));
+    }
+}
diff --git a/src/main/java/chain/processor/HRManager.java b/src/main/java/chain/processor/HRManager.java
@@ -0,0 +1,16 @@
+package chain.processor;
+
+import chain.handler.ApprovalHandler;
+import chain.service.impl.ExpenseAmountRuleService;
+import chain.service.impl.LeaveDaysRuleService;
+
+import java.util.Arrays;
+
+public class HRManager extends ApprovalHandler {
+    public HRManager() {
+        super(Arrays.asList(
+                new LeaveDaysRuleService(7),
+                new ExpenseAmountRuleService(1000)
+        ));
+    }
+}
diff --git a/src/main/java/chain/service/ApprovalRuleService.java b/src/main/java/chain/service/ApprovalRuleService.java
@@ -0,0 +1,9 @@
+package chain.service;
+
+import chain.dto.ApprovalRequestDto;
+
+public interface ApprovalRuleService {
+    boolean evaluate(ApprovalRequestDto request);
+
+    String getName();
+}
diff --git a/src/main/java/chain/service/impl/DefaultRuleService.java b/src/main/java/chain/service/impl/DefaultRuleService.java
@@ -0,0 +1,16 @@
+package chain.service.impl;
+
+import chain.dto.ApprovalRequestDto;
+import chain.service.ApprovalRuleService;
+
+public class DefaultRuleService implements ApprovalRuleService {
+    @Override
+    public boolean evaluate(ApprovalRequestDto request) {
+        return true;
+    }
+
+    @Override
+    public String getName() {
+        return "True";
+    }
+}
diff --git a/src/main/java/chain/service/impl/ExpenseAmountRuleService.java b/src/main/java/chain/service/impl/ExpenseAmountRuleService.java
@@ -0,0 +1,23 @@
+package chain.service.impl;
+
+import chain.dto.ApprovalRequestDto;
+import chain.enums.RequestType;
+import chain.service.ApprovalRuleService;
+
+public class ExpenseAmountRuleService implements ApprovalRuleService {
+    private final double maxAmount;
+
+    public ExpenseAmountRuleService(double maxAmount) {
+        this.maxAmount = maxAmount;
+    }
+
+    @Override
+    public boolean evaluate(ApprovalRequestDto req) {
+        return req.getType() == RequestType.EXPENSE && req.getAmount() <= maxAmount;
+    }
+
+    @Override
+    public String getName() {
+        return "Expense<=" + maxAmount;
+    }
+}
diff --git a/src/main/java/chain/service/impl/LeaveDaysRuleService.java b/src/main/java/chain/service/impl/LeaveDaysRuleService.java
@@ -0,0 +1,23 @@
+package chain.service.impl;
+
+import chain.dto.ApprovalRequestDto;
+import chain.enums.RequestType;
+import chain.service.ApprovalRuleService;
+
+public class LeaveDaysRuleService implements ApprovalRuleService {
+    private final int maxDays;
+
+    public LeaveDaysRuleService(int maxDays) {
+        this.maxDays = maxDays;
+    }
+
+    @Override
+    public boolean evaluate(ApprovalRequestDto req) {
+        return req.getType() == RequestType.LEAVE && req.getDays() <= maxDays;
+    }
+
+    @Override
+    public String getName() {
+        return "LeaveDays<=" + maxDays;
+    }
+}
diff --git a/src/main/java/chain/service/impl/PurchaseTypeRuleService.java b/src/main/java/chain/service/impl/PurchaseTypeRuleService.java
@@ -0,0 +1,17 @@
+package chain.service.impl;
+
+import chain.dto.ApprovalRequestDto;
+import chain.enums.RequestType;
+import chain.service.ApprovalRuleService;
+
+public class PurchaseTypeRuleService implements ApprovalRuleService {
+    @Override
+    public boolean evaluate(ApprovalRequestDto req) {
+        return req.getType() == RequestType.PURCHASE;
+    }
+
+    @Override
+    public String getName() {
+        return "Type==PURCHASE";
+    }
+}