diff --git a/src/main/java/xyz/zhouxy/plusone/commons/util/Arrays2.java b/src/main/java/xyz/zhouxy/plusone/commons/util/Arrays2.java
index 95eb458..d7dd4ee 100644
--- a/src/main/java/xyz/zhouxy/plusone/commons/util/Arrays2.java
+++ b/src/main/java/xyz/zhouxy/plusone/commons/util/Arrays2.java
@@ -16,42 +16,64 @@
 
 package xyz.zhouxy.plusone.commons.util;
 
+import java.util.Objects;
+
+import javax.annotation.Nonnull;
+
 public abstract class Arrays2 {
 
     @SafeVarargs
+    @Nonnull
     public static <T> T[] of(final T... values) {
+        Objects.requireNonNull(values);
         return values;
     }
 
+    @Nonnull
     public static short[] of(final short... values) {
+        Objects.requireNonNull(values);
         return values;
     }
 
+    @Nonnull
     public static int[] of(final int... values) {
+        Objects.requireNonNull(values);
         return values;
     }
 
+    @Nonnull
     public static long[] of(final long... values) {
+        Objects.requireNonNull(values);
         return values;
     }
 
+    @Nonnull
     public static byte[] of(final byte... values) {
+        Objects.requireNonNull(values);
         return values;
     }
 
+    @Nonnull
     public static boolean[] of(final boolean... values) {
+        Objects.requireNonNull(values);
         return values;
     }
 
+    @Nonnull
     public static char[] of(final char... values) {
+        Objects.requireNonNull(values);
         return values;
     }
 
+    @Nonnull
     public static double[] of(final double... values) {
+        Objects.requireNonNull(values);
         return values;
     }
 
+    @Nonnull
     public static float[] of(final float... values) {
+        Objects.requireNonNull(values);
         return values;
     }
 
diff --git a/src/main/java/xyz/zhouxy/plusone/commons/util/EnumUtil.java b/src/main/java/xyz/zhouxy/plusone/commons/util/EnumUtil.java
index 7135319..30ad4ab 100644
--- a/src/main/java/xyz/zhouxy/plusone/commons/util/EnumUtil.java
+++ b/src/main/java/xyz/zhouxy/plusone/commons/util/EnumUtil.java
@@ -18,6 +18,9 @@ package xyz.zhouxy.plusone.commons.util;
 
 import java.util.Objects;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
 /**
  * 枚举工具类
  *
@@ -37,7 +40,7 @@ public final class EnumUtil {
      * @param ordinal 数据库中对应的数值
      * @return 枚举对象
      */
-    public static <E extends Enum<?>> E valueOf(Class<E> clazz, int ordinal) {
+    public static <E extends Enum<?>> E valueOf(@Nonnull Class<E> clazz, int ordinal) {
         E[] values = clazz.getEnumConstants();
         try {
             return values[ordinal];
@@ -54,11 +57,12 @@ public final class EnumUtil {
      * @param ordinal 数据库中对应的数值
      * @return 枚举对象
      */
-    public static <E extends Enum<?>> E getValueOrDefault(Class<E> clazz, Integer ordinal) {
+    public static <E extends Enum<?>> E getValueOrDefault(@Nonnull Class<E> clazz, @Nullable Integer ordinal) {
         E[] values = clazz.getEnumConstants();
         try {
             return Objects.nonNull(ordinal) ? values[ordinal] : values[0];
         } catch (IndexOutOfBoundsException e) {
+            Objects.requireNonNull(ordinal);
             throw new EnumConstantNotPresentException(clazz, Integer.toString(ordinal));
         }
     }
@@ -71,19 +75,17 @@ public final class EnumUtil {
      * @param ordinal 数据库中对应的数值
      * @return 枚举对象
      */
-    public static <E extends Enum<?>> E getValueNullable(Class<E> clazz, Integer ordinal) {
+    public static <E extends Enum<?>> E getValueNullable(@Nonnull Class<E> clazz, @Nullable Integer ordinal) {
         E[] values = clazz.getEnumConstants();
         try {
             return Objects.nonNull(ordinal) ? values[ordinal] : null;
         } catch (IndexOutOfBoundsException e) {
+            Objects.requireNonNull(ordinal);
             throw new EnumConstantNotPresentException(clazz, Integer.toString(ordinal));
         }
     }
 
-    public static <E extends Enum<?>> Integer checkOrdinal(Class<E> clazz, Integer ordinal) {
-        if (ordinal == null) {
-            throw new IllegalArgumentException("ordinal 不能为空");
-        }
+    public static <E extends Enum<?>> Integer checkOrdinal(@Nonnull Class<E> clazz, @Nonnull Integer ordinal) {
         E[] values = clazz.getEnumConstants();
         if (ordinal >= 0 && ordinal < values.length) {
             return ordinal;
@@ -91,15 +93,15 @@ public final class EnumUtil {
         throw new EnumConstantNotPresentException(clazz, Integer.toString(ordinal));
     }
 
-    public static <E extends Enum<?>> Integer checkOrdinalNullable(Class<E> clazz, Integer ordinal) {
-        if (Objects.isNull(ordinal)) {
+    public static <E extends Enum<?>> Integer checkOrdinalNullable(@Nonnull Class<E> clazz, @Nullable Integer ordinal) {
+        if (ordinal == null) {
             return null;
         }
         return checkOrdinal(clazz, ordinal);
     }
 
-    public static <E extends Enum<?>> Integer checkOrdinalOrDefault(Class<E> clazz, Integer ordinal) {
-        if (Objects.isNull(ordinal)) {
+    public static <E extends Enum<?>> Integer checkOrdinalOrDefault(@Nonnull Class<E> clazz, @Nullable Integer ordinal) {
+        if (ordinal == null) {
             return 0;
         }
         return checkOrdinal(clazz, ordinal);
diff --git a/src/main/java/xyz/zhouxy/plusone/commons/util/Enumeration.java b/src/main/java/xyz/zhouxy/plusone/commons/util/Enumeration.java
index b1255d3..397f888 100644
--- a/src/main/java/xyz/zhouxy/plusone/commons/util/Enumeration.java
+++ b/src/main/java/xyz/zhouxy/plusone/commons/util/Enumeration.java
@@ -20,14 +20,17 @@ import java.util.Map;
 import java.util.Objects;
 import java.util.concurrent.ConcurrentHashMap;
 
+import javax.annotation.Nonnull;
+
 /**
  * 枚举类
  */
 public abstract class Enumeration<T extends Enumeration<T>> {
     protected final int value;
+    @Nonnull
     protected final String name;
 
-    protected Enumeration(int value, String name) {
+    protected Enumeration(int value, @Nonnull String name) {
         this.value = value;
         this.name = name;
     }
@@ -36,6 +39,7 @@ public abstract class Enumeration<T extends Enumeration<T>> {
         return value;
     }
 
+    @Nonnull
     public String getName() {
         return name;
     }
@@ -68,16 +72,20 @@ public abstract class Enumeration<T extends Enumeration<T>> {
         @SafeVarargs
         public EnumerationValuesHolder(T... values) {
             for (T value : values) {
+                Objects.requireNonNull(value);
                 put(value);
             }
         }
     
-        private void put(T constant) {
+        private void put(@Nonnull T constant) {
             this.constants.put(constant.getValue(), constant);
         }
-    
+
+        @Nonnull
         public T get(int value) {
-            return this.constants.get(value);
+            T val = this.constants.get(value);
+            Objects.requireNonNull(val);
+            return val;
         }
     }
 }
diff --git a/src/main/java/xyz/zhouxy/plusone/commons/util/NumberUtil.java b/src/main/java/xyz/zhouxy/plusone/commons/util/NumberUtil.java
index 088e005..1395050 100644
--- a/src/main/java/xyz/zhouxy/plusone/commons/util/NumberUtil.java
+++ b/src/main/java/xyz/zhouxy/plusone/commons/util/NumberUtil.java
@@ -27,7 +27,7 @@ public class NumberUtil {
         throw new IllegalStateException("Utility class");
     }
 
-    public static int sum(short... numbers) {
+    public static int sum(final short... numbers) {
         int result = 0;
         for (short number : numbers) {
             result += number;
@@ -35,7 +35,7 @@ public class NumberUtil {
         return result;
     }
 
-    public static long sum(int... numbers) {
+    public static long sum(final int... numbers) {
         int result = 0;
         for (int number : numbers) {
             result += number;
@@ -43,7 +43,7 @@ public class NumberUtil {
         return result;
     }
 
-    public static long sum(long... numbers) {
+    public static long sum(final long... numbers) {
         long result = 0;
         for (long number : numbers) {
             result += number;
@@ -51,7 +51,7 @@ public class NumberUtil {
         return result;
     }
 
-    public static double sum(float... numbers) {
+    public static double sum(final float... numbers) {
         double result = 0;
         for (double number : numbers) {
             result += number;
@@ -59,7 +59,7 @@ public class NumberUtil {
         return result;
     }
 
-    public static double sum(double... numbers) {
+    public static double sum(final double... numbers) {
         double result = 0;
         for (double number : numbers) {
             result += number;
diff --git a/src/main/java/xyz/zhouxy/plusone/commons/util/PageDTO.java b/src/main/java/xyz/zhouxy/plusone/commons/util/PageDTO.java
index 049658e..e737013 100644
--- a/src/main/java/xyz/zhouxy/plusone/commons/util/PageDTO.java
+++ b/src/main/java/xyz/zhouxy/plusone/commons/util/PageDTO.java
@@ -18,6 +18,8 @@ package xyz.zhouxy.plusone.commons.util;
 
 import java.util.List;
 
+import javax.annotation.Nonnull;
+
 /**
  * 返回分页查询的结果
  *
@@ -28,38 +30,31 @@ import java.util.List;
  */
 public class PageDTO<T> {
 
-    private Long total;
-    private List<T> content;
+    @Nonnull
+    private final Long total;
+    @Nonnull
+    private final List<T> content;
 
-    private PageDTO(List<T> content, Long total) {
+    private PageDTO(@Nonnull List<T> content, @Nonnull Long total) {
         this.content = content;
         this.total = total;
     }
 
-    public static <T> PageDTO<T> of(List<T> content, Long total) {
+    @Nonnull
+    public static <T> PageDTO<T> of(@Nonnull List<T> content, @Nonnull Long total) {
         return new PageDTO<>(content, total);
     }
 
+    @Nonnull
     public Long getTotal() {
         return total;
     }
 
+    @Nonnull
     public List<T> getContent() {
         return content;
     }
 
-    // Setters
-
-    public void setTotal(Long total) {
-        this.total = total;
-    }
-
-    public void setContent(List<T> content) {
-        this.content = content;
-    }
-
-    // Setters end
-
     @Override
     public String toString() {
         return "PageDTO [total=" + total + ", content=" + content + "]";
diff --git a/src/main/java/xyz/zhouxy/plusone/commons/util/PagingAndSortingQueryParams.java b/src/main/java/xyz/zhouxy/plusone/commons/util/PagingAndSortingQueryParams.java
index 5959189..cdfe472 100644
--- a/src/main/java/xyz/zhouxy/plusone/commons/util/PagingAndSortingQueryParams.java
+++ b/src/main/java/xyz/zhouxy/plusone/commons/util/PagingAndSortingQueryParams.java
@@ -47,6 +47,8 @@ public class PagingAndSortingQueryParams {
         this.sortableColNames = Arrays.asList(sortableColNames);
     }
 
+    // Getters
+
     public String getOrderBy() {
         return orderBy != null && sortableColNames.contains(orderBy) ? orderBy : null;
     }
@@ -63,6 +65,8 @@ public class PagingAndSortingQueryParams {
         return (getPageNum() - 1) * getSize();
     }
 
+    // Getters end
+
     // Setters
 
     public void setOrderBy(String orderBy) {
diff --git a/src/main/java/xyz/zhouxy/plusone/commons/util/RestfulResult.java b/src/main/java/xyz/zhouxy/plusone/commons/util/RestfulResult.java
index 7a8b5f1..e967a21 100644
--- a/src/main/java/xyz/zhouxy/plusone/commons/util/RestfulResult.java
+++ b/src/main/java/xyz/zhouxy/plusone/commons/util/RestfulResult.java
@@ -19,6 +19,9 @@ package xyz.zhouxy.plusone.commons.util;
 import java.util.function.BooleanSupplier;
 import java.util.function.Supplier;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
 import com.fasterxml.jackson.annotation.JsonInclude;
 
 /**
@@ -32,59 +35,83 @@ public class RestfulResult {
     public static final int SUCCESS_STATUS = 2000000;
     public static final int DEFAULT_ERROR_STATUS = 9999999;
 
+    @Nonnull
     private final Object status;
+    @Nonnull
     private final String message;
+    @Nullable
     private final Object data;
 
-    private RestfulResult(final Object status, final String message) {
+    private RestfulResult(@Nonnull final Object status, @Nonnull final String message) {
         this(status, message, null);
     }
 
+    @Nonnull
     public static RestfulResult success() {
         return new RestfulResult(SUCCESS_STATUS, "操作成功");
     }
 
-    public static RestfulResult success(final String message) {
+    @Nonnull
+    public static RestfulResult success(@Nonnull final String message) {
         return new RestfulResult(SUCCESS_STATUS, message);
     }
 
-    public static RestfulResult success(final String message, final Object data) {
+    @Nonnull
+    public static RestfulResult success(
+            @Nonnull final String message,
+            @Nullable final Object data) {
         return new RestfulResult(SUCCESS_STATUS, message, data);
     }
 
+    @Nonnull
     public static RestfulResult error() {
         return new RestfulResult(DEFAULT_ERROR_STATUS, "未知错误");
     }
 
-    public static RestfulResult error(final Object status, final String message) {
+    @Nonnull
+    public static RestfulResult error(
+            @Nonnull final Object status,
+            @Nonnull final String message) {
         return new RestfulResult(status, message);
     }
 
-    public static RestfulResult error(final Object status, final String message, final Object data) {
+    @Nonnull
+    public static RestfulResult error(
+            @Nonnull final Object status,
+            @Nonnull final String message,
+            @Nullable final Object data) {
         return new RestfulResult(status, message, data);
     }
 
-    public static RestfulResult error(final Object status, final Throwable e) {
-        return new RestfulResult(status, e.getMessage());
+    @Nonnull
+    public static RestfulResult error(@Nonnull final Object status, @Nonnull final Throwable e) {
+        String msg = e.getMessage();
+        if (msg == null) {
+            msg = "";
+        }
+        return new RestfulResult(status, msg);
     }
 
     public static RestfulResult of(
             final boolean isSuccess,
-            final Supplier<RestfulResult> success,
-            final Supplier<RestfulResult> error) {
+            @Nonnull final Supplier<RestfulResult> success,
+            @Nonnull final Supplier<RestfulResult> error) {
         return isSuccess ? success.get() : error.get();
     }
 
     public static RestfulResult of(
-            final BooleanSupplier isSuccess,
-            final Supplier<RestfulResult> success,
-            final Supplier<RestfulResult> error) {
+            @Nonnull final BooleanSupplier isSuccess,
+            @Nonnull final Supplier<RestfulResult> success,
+            @Nonnull final Supplier<RestfulResult> error) {
         return isSuccess.getAsBoolean() ? success.get() : error.get();
     }
 
     // Constructors
 
-    private RestfulResult(Object status, String message, Object data) {
+    private RestfulResult(
+            @Nonnull final Object status,
+            @Nonnull final String message,
+            @Nullable final Object data) {
         this.status = status;
         this.message = message;
         this.data = data;
@@ -94,14 +121,17 @@ public class RestfulResult {
 
     // Getters
 
+    @Nonnull
     public Object getStatus() {
         return status;
     }
 
+    @Nonnull
     public String getMessage() {
         return message;
     }
 
+    @Nullable
     public Object getData() {
         return data;
     }
@@ -112,59 +142,4 @@ public class RestfulResult {
     public String toString() {
         return "RestfulResult [status=" + status + ", message=" + message + ", data=" + data + "]";
     }
-
-    // Builder
-    public static Builder successIf(final boolean condition) {
-        return successIf(() -> condition);
-    }
-
-    public static Builder successIf(final BooleanSupplier booleanSupplier) {
-        return new Builder(booleanSupplier, () -> success());
-    }
-
-    public static Builder successIf(final boolean condition, final String msg) {
-        return new Builder(() -> condition, () -> success(msg));
-    }
-
-    public static Builder successIf(final BooleanSupplier booleanSupplier, final String msg) {
-        return new Builder(booleanSupplier, () -> success(msg));
-    }
-
-    public static Builder successIf(final boolean condition, final String msg, final Object data) {
-        return new Builder(() -> condition, () -> success(msg, data));
-    }
-
-    public static Builder successIf(final BooleanSupplier booleanSupplier, final String msg, final Object data) {
-        return new Builder(booleanSupplier, () -> success(msg, data));
-    }
-
-    public static class Builder {
-        private final BooleanSupplier booleanSupplier;
-        private final Supplier<RestfulResult> success;
-
-        public Builder(final BooleanSupplier booleanSupplier, final Supplier<RestfulResult> success) {
-            this.booleanSupplier = booleanSupplier;
-            this.success = success;
-        }
-
-        public RestfulResult orError() {
-            return this.booleanSupplier.getAsBoolean()
-                    ? this.success.get()
-                    : RestfulResult.error();
-        }
-
-        public RestfulResult orError(final Object status, final String msg) {
-            return orError(status, msg, null);
-        }
-
-        public RestfulResult orError(final Object status, final Throwable e) {
-            return orError(status, e.getMessage());
-        }
-
-        public RestfulResult orError(final Object status, final String msg, final Object data) {
-            return this.booleanSupplier.getAsBoolean()
-                    ? this.success.get()
-                    : RestfulResult.error(status, msg, data);
-        }
-    }
 }
diff --git a/src/test/java/xyz/zhouxy/plusone/commons/EnumerationTests.java b/src/test/java/xyz/zhouxy/plusone/commons/EnumerationTests.java
index 6e950a7..0ab1334 100644
--- a/src/test/java/xyz/zhouxy/plusone/commons/EnumerationTests.java
+++ b/src/test/java/xyz/zhouxy/plusone/commons/EnumerationTests.java
@@ -2,6 +2,8 @@ package xyz.zhouxy.plusone.commons;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
+import javax.annotation.Nonnull;
+
 import org.junit.jupiter.api.Test;
 
 import xyz.zhouxy.plusone.commons.util.Enumeration;
@@ -16,7 +18,7 @@ class EnumerationTests {
 
 final class EntityStatus extends Enumeration<EntityStatus> {
 
-    private EntityStatus(int value, String name) {
+    private EntityStatus(int value, @Nonnull String name) {
         super(value, name);
     }
 
diff --git a/src/test/java/xyz/zhouxy/plusone/commons/util/RestfulResultTest.java b/src/test/java/xyz/zhouxy/plusone/commons/util/RestfulResultTest.java
deleted file mode 100644
index 177d05a..0000000
--- a/src/test/java/xyz/zhouxy/plusone/commons/util/RestfulResultTest.java
+++ /dev/null
@@ -1,34 +0,0 @@
-package xyz.zhouxy.plusone.commons.util;
-
-import static org.junit.jupiter.api.Assertions.assertEquals;
-
-import org.junit.jupiter.api.Test;
-
-class RestfulResultTest {
-
-    @Test
-    void testSuccessIf() {
-        String str = null;
-        RestfulResult result = RestfulResult.successIf(str != null, "成功")
-                .orError();
-        System.out.println(result);
-        assertEquals(RestfulResult.DEFAULT_ERROR_STATUS, result.getStatus());
-
-        result = RestfulResult.successIf(str != null, "成功")
-                .orError(2333, "失败");
-        System.out.println(result);
-        assertEquals(2333, result.getStatus());
-        assertEquals("失败", result.getMessage());
-
-        str = "";
-        result = RestfulResult.successIf(str != null, "成功")
-                .orError();
-        System.out.println(result);
-        assertEquals(RestfulResult.SUCCESS_STATUS, result.getStatus());
-
-        result = RestfulResult.successIf(str != null, "成功", str)
-                .orError(2333, "失败");
-        System.out.println(result);
-        assertEquals("成功", result.getMessage());
-    }
-}