diff --git a/src/main/java/xyz/zhouxy/plusone/commons/model/Chinese2ndGenIDCardNumber.java b/src/main/java/xyz/zhouxy/plusone/commons/model/Chinese2ndGenIDCardNumber.java
index deb8eed..27a1c29 100644
--- a/src/main/java/xyz/zhouxy/plusone/commons/model/Chinese2ndGenIDCardNumber.java
+++ b/src/main/java/xyz/zhouxy/plusone/commons/model/Chinese2ndGenIDCardNumber.java
@@ -21,6 +21,8 @@ import java.time.format.DateTimeFormatter;
 import java.util.Map;
 import java.util.regex.Matcher;
 
+import javax.annotation.Nullable;
+
 import com.google.common.base.Strings;
 import com.google.common.collect.ImmutableMap;
 import com.google.errorprone.annotations.Immutable;
@@ -207,7 +209,7 @@ public class Chinese2ndGenIDCardNumber
     }
 
     @Override
-    public boolean equals(Object obj) {
+    public boolean equals(@Nullable Object obj) {
         return super.equals(obj);
     }
 }
diff --git a/src/main/java/xyz/zhouxy/plusone/commons/model/ValidatableStringRecord.java b/src/main/java/xyz/zhouxy/plusone/commons/model/ValidatableStringRecord.java
index 4db3c28..d604399 100644
--- a/src/main/java/xyz/zhouxy/plusone/commons/model/ValidatableStringRecord.java
+++ b/src/main/java/xyz/zhouxy/plusone/commons/model/ValidatableStringRecord.java
@@ -22,6 +22,7 @@ import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 
 import xyz.zhouxy.plusone.commons.annotation.ReaderMethod;
 import xyz.zhouxy.plusone.commons.util.AssertTools;
@@ -40,17 +41,16 @@ public abstract class ValidatableStringRecord<T extends ValidatableStringRecord<
 
     private final Matcher matcher;
 
-    protected ValidatableStringRecord(@Nonnull String value, @Nonnull Pattern pattern) {
+    protected ValidatableStringRecord(String value, Pattern pattern) {
         this(value, pattern, "Invalid value");
     }
 
-    protected ValidatableStringRecord(@Nonnull String value, @Nonnull Pattern pattern,
-            @Nonnull Supplier<String> errorMessageSupplier) {
+    protected ValidatableStringRecord(String value, Pattern pattern,
+            Supplier<String> errorMessageSupplier) {
         this(value, pattern, errorMessageSupplier.get());
     }
 
-    protected ValidatableStringRecord(@Nonnull String value, @Nonnull Pattern pattern,
-            @Nonnull String errorMessage) {
+    protected ValidatableStringRecord(String value, Pattern pattern, String errorMessage) {
         AssertTools.checkArgument(Objects.nonNull(value), "The value cannot be null.");
         AssertTools.checkArgument(Objects.nonNull(pattern), "The pattern cannot be null.");
         this.matcher = pattern.matcher(value);
@@ -69,7 +69,7 @@ public abstract class ValidatableStringRecord<T extends ValidatableStringRecord<
     }
 
     @Override
-    public int compareTo(T o) {
+    public int compareTo(@SuppressWarnings("null") T o) {
         return this.value.compareTo(o.value());
     }
 
@@ -79,7 +79,7 @@ public abstract class ValidatableStringRecord<T extends ValidatableStringRecord<
     }
 
     @Override
-    public boolean equals(Object obj) {
+    public boolean equals(@Nullable Object obj) {
         if (this == obj)
             return true;
         if (obj == null)
diff --git a/src/main/java/xyz/zhouxy/plusone/commons/model/dto/PageResult.java b/src/main/java/xyz/zhouxy/plusone/commons/model/dto/PageResult.java
index 353d86f..4c1a061 100644
--- a/src/main/java/xyz/zhouxy/plusone/commons/model/dto/PageResult.java
+++ b/src/main/java/xyz/zhouxy/plusone/commons/model/dto/PageResult.java
@@ -19,6 +19,8 @@ package xyz.zhouxy.plusone.commons.model.dto;
 import java.util.Collections;
 import java.util.List;
 
+import javax.annotation.Nullable;
+
 import xyz.zhouxy.plusone.commons.annotation.StaticFactoryMethod;
 import xyz.zhouxy.plusone.commons.collection.CollectionTools;
 
@@ -36,13 +38,13 @@ public class PageResult<T> {
 
     private final List<T> content;
 
-    private PageResult(List<T> content, long total) {
+    private PageResult(@Nullable final List<T> content, final long total) {
         this.content = CollectionTools.nullToEmptyList(content);
         this.total = total;
     }
 
     @StaticFactoryMethod(PageResult.class)
-    public static <T> PageResult<T> of(List<T> content, long total) {
+    public static <T> PageResult<T> of(@Nullable final List<T> content, final long total) {
         return new PageResult<>(content, total);
     }
 
diff --git a/src/main/java/xyz/zhouxy/plusone/commons/model/dto/PagingAndSortingQueryParams.java b/src/main/java/xyz/zhouxy/plusone/commons/model/dto/PagingAndSortingQueryParams.java
index 6eb0106..71e36af 100644
--- a/src/main/java/xyz/zhouxy/plusone/commons/model/dto/PagingAndSortingQueryParams.java
+++ b/src/main/java/xyz/zhouxy/plusone/commons/model/dto/PagingAndSortingQueryParams.java
@@ -21,7 +21,6 @@ import java.util.Map;
 import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 
-import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 
 import com.google.common.collect.ImmutableMap;
@@ -55,7 +54,7 @@ public class PagingAndSortingQueryParams {
 
     private final Map<String, String> sortableProperties;
 
-    public PagingAndSortingQueryParams(@Nonnull Map<String, String> sortableProperties) {
+    public PagingAndSortingQueryParams(Map<String, String> sortableProperties) {
         AssertTools.checkArgument(CollectionTools.isNotEmpty(sortableProperties),
                 "Sortable properties can not be empty.");
         sortableProperties.forEach((k, v) ->
@@ -66,7 +65,12 @@ public class PagingAndSortingQueryParams {
 
     // Setters
 
-    public final void setOrderBy(@Nullable List<String> orderBy) {
+    /**
+     * 设置排序规则
+     *
+     * @param orderBy 排序规则，不能为空
+     */
+    public final void setOrderBy(List<String> orderBy) {
         this.orderBy = orderBy;
     }
 
@@ -83,7 +87,10 @@ public class PagingAndSortingQueryParams {
     public final PagingParams buildPagingParams() {
         final int sizeValue = this.size != null ? this.size : defaultSizeInternal();
         final long pageNumValue = this.pageNum != null ? this.pageNum : 1L;
-        final List<SortableProperty> propertiesToSort = this.orderBy.stream().map(this::generateSortableProperty)
+        AssertTools.checkArgument(CollectionTools.isNotEmpty(this.orderBy),
+                "The 'orderBy' cannot be empty");
+        final List<SortableProperty> propertiesToSort = this.orderBy.stream()
+                .map(this::generateSortableProperty)
                 .collect(Collectors.toList());
         return new PagingParams(sizeValue, pageNumValue, propertiesToSort);
     }
@@ -104,6 +111,7 @@ public class PagingAndSortingQueryParams {
     }
 
     private SortableProperty generateSortableProperty(String orderByStr) {
+        AssertTools.checkArgument(StringTools.isNotBlank(orderByStr));
         AssertTools.checkArgument(RegexTools.matches(orderByStr, SORT_STR_PATTERN));
         String[] propertyNameAndOrderType = orderByStr.split("-");
         AssertTools.checkArgument(propertyNameAndOrderType.length == 2);
diff --git a/src/main/java/xyz/zhouxy/plusone/commons/model/dto/UnifiedResponse.java b/src/main/java/xyz/zhouxy/plusone/commons/model/dto/UnifiedResponse.java
index bd60a41..83a259e 100644
--- a/src/main/java/xyz/zhouxy/plusone/commons/model/dto/UnifiedResponse.java
+++ b/src/main/java/xyz/zhouxy/plusone/commons/model/dto/UnifiedResponse.java
@@ -76,7 +76,7 @@ public class UnifiedResponse<T> {
                 this.code, this.message, transValue(this.data));
     }
 
-    private static String transValue(Object value) {
+    private static String transValue(@Nullable Object value) {
         if (value == null) {
             return null;
         }
diff --git a/src/main/java/xyz/zhouxy/plusone/commons/model/dto/package-info.java b/src/main/java/xyz/zhouxy/plusone/commons/model/dto/package-info.java
index a8012a7..0296dc2 100644
--- a/src/main/java/xyz/zhouxy/plusone/commons/model/dto/package-info.java
+++ b/src/main/java/xyz/zhouxy/plusone/commons/model/dto/package-info.java
@@ -64,4 +64,7 @@
  *
  * @author <a href="http://zhouxy.xyz:3000/ZhouXY108">ZhouXY</a>
  */
+@ParametersAreNonnullByDefault
 package xyz.zhouxy.plusone.commons.model.dto;
+
+import javax.annotation.ParametersAreNonnullByDefault;
diff --git a/src/main/java/xyz/zhouxy/plusone/commons/model/package-info.java b/src/main/java/xyz/zhouxy/plusone/commons/model/package-info.java
index d3112a9..c3f1fb6 100644
--- a/src/main/java/xyz/zhouxy/plusone/commons/model/package-info.java
+++ b/src/main/java/xyz/zhouxy/plusone/commons/model/package-info.java
@@ -22,4 +22,7 @@
  *
  * @author <a href="http://zhouxy.xyz:3000/ZhouXY108">ZhouXY</a>
  */
+@ParametersAreNonnullByDefault
 package xyz.zhouxy.plusone.commons.model;
+
+import javax.annotation.ParametersAreNonnullByDefault;