diff --git a/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/Mapping.java b/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/Mapping.java
index 4e24d78..70c2f93 100644
--- a/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/Mapping.java
+++ b/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/Mapping.java
@@ -122,6 +122,17 @@ public final void removeComponent(@NotNull Class<? extends Component> component)
         components.remove(Objects.requireNonNull(component));
     }
 
+    /**
+     * Validates all the components of this mapping
+     *
+     * @throws IllegalStateException If any of the component fails validation
+     */
+    public final void validateComponents() throws IllegalStateException {// TODO
+        for (Component value : components.values()) {
+            value.validate();
+        }
+    }
+
     /* Auto-generated equals, hashCode and toString methods */
     @Override
     public boolean equals(Object o) {
diff --git a/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Component.java b/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Component.java
index 635829b..0820bc0 100644
--- a/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Component.java
+++ b/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Component.java
@@ -26,6 +26,6 @@ public interface Component {
      * Validates this component.
      * @throws IllegalStateException if the validation fails
      */
-    default void validate() throws IllegalStateException {// TODO: component validation
+    default void validate() throws IllegalStateException {
     }
 }
\ No newline at end of file
diff --git a/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Documented.java b/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Documented.java
index a0bcb0a..1f80243 100644
--- a/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Documented.java
+++ b/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Documented.java
@@ -35,13 +35,13 @@ public class Documented implements Component {
     /**
      * The contents
      */
-    public final ObjectArrayList<String> contents = new ObjectArrayList<>();
+    public final ObjectArrayList<@NotNull String> contents = new ObjectArrayList<>();
 
     /**
      * Gets the contents
      * @return The contents
      */
-    public List<String> getContents() {
+    public List<@NotNull String> getContents() {
         return contents;
     }
 
@@ -67,11 +67,19 @@ public void setContentString(@NotNull String content) {
         if (mark < content.length()) contents.add(content.substring(mark));
     }
 
+    @Override
+    public void validate() throws IllegalStateException {
+        for (String content : contents) {
+            if (content.indexOf('\n') != -1 || content.indexOf('\r') != -1)
+                throw new IllegalStateException("The document contains invalid characters");
+        }
+    }
+
     @Override
     public boolean equals(Object o) {
         if (this == o) return true;
         if (!(o instanceof Documented that)) return false;
-        return Objects.equals(contents, that.contents);
+        return contents.equals(that.contents);
     }
 
     @Override
diff --git a/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/LineNumber.java b/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/LineNumber.java
index bdafc9f..d4b33db 100644
--- a/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/LineNumber.java
+++ b/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/LineNumber.java
@@ -46,6 +46,12 @@ public void setEndLineNumber(int endLineNumber) {
         this.endLineNumber = endLineNumber;
     }
 
+    @Override
+    public void validate() throws IllegalStateException {
+        if (startLineNumber < 0 || endLineNumber < 0 || startLineNumber > endLineNumber)
+            throw new IllegalStateException("Invalid line number");
+    }
+
     @Override
     public boolean equals(Object o) {
         if (this == o) return true;
diff --git a/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/LocalVariableTable.java b/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/LocalVariableTable.java
index 6195769..220aa83 100644
--- a/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/LocalVariableTable.java
+++ b/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/LocalVariableTable.java
@@ -82,6 +82,14 @@ public String toString() {
     }
 
     public static class Paired extends LocalVariableTable<PairedMapping> implements Component {
+        @Override
+        public void validate() throws IllegalStateException {
+            lvt.int2ObjectEntrySet().fastForEach(entry -> {
+                if (entry.getIntKey() < 0 || entry.getIntKey() > 255) throw new IllegalStateException();
+                entry.getValue().validateComponents();
+            });
+        }
+
         public void reverse() {
             lvt.values().forEach(PairedMapping::reverse);
         }
@@ -133,6 +141,16 @@ public void setFallbackNamespace(@NotNull String namespace) {
             }
         }
 
+        @Override
+        public void validate() throws IllegalStateException {
+            if (unmappedNamespace == null) throw new IllegalStateException();
+            lvt.int2ObjectEntrySet().fastForEach(entry -> {
+                if (entry.getIntKey() < 0 || entry.getIntKey() > 255)
+                    throw new IllegalStateException("Illegal LVT index");
+                entry.getValue().validateComponents();
+            });
+        }
+
         @Override
         public boolean equals(Object o) {
             if (this == o) return true;
diff --git a/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Owned.java b/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Owned.java
index 9d0174a..7222d60 100644
--- a/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Owned.java
+++ b/modules/mapping-api/src/main/java/cn/maxpixel/mcdecompiler/mapping/component/Owned.java
@@ -40,6 +40,11 @@ public void setOwner(ClassMapping<T> owner) {
         this.owner = owner;
     }
 
+    @Override
+    public void validate() throws IllegalStateException {
+        if (owner == null) throw new IllegalStateException("Owner is null");
+    }
+
     @Override
     public boolean equals(Object o) {
         if (this == o) return true;