feat(structs): add OGNL binding lab and deepen interceptor learning page

src/main/java/com/example/struts2/OgnlLabAction.java

@@ -0,0 +1,71 @@
+package com.example.struts2;
+
+import com.opensymphony.xwork2.ActionSupport;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class OgnlLabAction extends ActionSupport {
+    private String keyword;
+    private Integer minAge;
+    private DemoUser user = new DemoUser();
+    private List<String> tags = new ArrayList<>();
+    private List<DemoUser> users;
+    private List<DemoUser> filteredUsers;
+
+    public String execute() {
+        loadUsers();
+        filteredUsers = users;
+        return SUCCESS;
+    }
+
+    public String bind() {
+        loadUsers();
+        filteredUsers = users.stream()
+                .filter(u -> keyword == null || keyword.isBlank() || u.getName().contains(keyword) || u.getEmail().contains(keyword))
+                .filter(u -> minAge == null || u.getAge() >= minAge)
+                .collect(Collectors.toList());
+        return SUCCESS;
+    }
+
+    private void loadUsers() {
+        users = Arrays.asList(
+                new DemoUser("张三", "zhangsan@example.com", 22),
+                new DemoUser("李四", "lisi@example.com", 28),
+                new DemoUser("王五", "wangwu@example.com", 34),
+                new DemoUser("赵六", "zhaoliu@example.com", 19)
+        );
+    }
+
+    public static class DemoUser {
+        private String name;
+        private String email;
+        private Integer age;
+
+        public DemoUser() {}
+        public DemoUser(String name, String email, Integer age) {
+            this.name = name;
+            this.email = email;
+            this.age = age;
+        }
+        public String getName() { return name; }
+        public void setName(String name) { this.name = name; }
+        public String getEmail() { return email; }
+        public void setEmail(String email) { this.email = email; }
+        public Integer getAge() { return age; }
+        public void setAge(Integer age) { this.age = age; }
+    }
+
+    public String getKeyword() { return keyword; }
+    public void setKeyword(String keyword) { this.keyword = keyword; }
+    public Integer getMinAge() { return minAge; }
+    public void setMinAge(Integer minAge) { this.minAge = minAge; }
+    public DemoUser getUser() { return user; }
+    public void setUser(DemoUser user) { this.user = user; }
+    public List<String> getTags() { return tags; }
+    public void setTags(List<String> tags) { this.tags = tags; }
+    public List<DemoUser> getUsers() { return users; }
+    public List<DemoUser> getFilteredUsers() { return filteredUsers; }
+}