使用Java的文件随机访问功能防止读取整个IP数据库到内存

src/main/java/net/ipip/ipdb/BaseStation.java

@@ -1,5 +1,6 @@
 package net.ipip.ipdb;
 
+import java.io.Closeable;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Arrays;
@@ -14,7 +15,7 @@ public class BaseStation {
     private Reader reader;
 
     public BaseStation(String name) throws IOException,InvalidDatabaseException {
-        this.reader = new Reader(name);
+        this.reader = new RandomAccessReader(name);
     }
 
     public BaseStation(InputStream in) throws IOException, InvalidDatabaseException {
@@ -23,8 +24,11 @@ public BaseStation(InputStream in) throws IOException, InvalidDatabaseException
 
     public boolean reload(String name) {
         try {
-            Reader r = new Reader(name);
-            this.reader = r;
+        	Reader old = this.reader;
+            this.reader = new RandomAccessReader(name);
+            if (old instanceof Closeable) {
+        		((Closeable) old).close();
+        	}
         } catch (Exception e) {
             return false;
         }

src/main/java/net/ipip/ipdb/City.java

@@ -1,6 +1,7 @@
 package net.ipip.ipdb;
 
 import java.io.InputStream;
+import java.io.Closeable;
 import java.io.IOException;
 import java.util.Arrays;
 import java.util.HashMap;
@@ -14,7 +15,7 @@ public class City {
     private Reader reader;
 
     public City(String name) throws IOException,InvalidDatabaseException {
-        this.reader = new Reader(name);
+        this.reader = new RandomAccessReader(name);
     }
 
     public City(InputStream in) throws IOException,InvalidDatabaseException {
@@ -23,8 +24,11 @@ public City(InputStream in) throws IOException,InvalidDatabaseException {
 
     public boolean reload(String name) {
         try {
-            Reader r = new Reader(name);
-            this.reader = r;
+        	Reader old = this.reader;
+            this.reader = new RandomAccessReader(name);
+            if (old instanceof Closeable) {
+        		((Closeable) old).close();
+        	}
         } catch (Exception e) {
             return false;
         }

src/main/java/net/ipip/ipdb/CityInfo.java

@@ -249,7 +249,8 @@ public DistrictInfo getDistrictInfo() {
             if (str == null) {
                 return null;
             }
-            Map<String,String> info = JSONObject.parseObject(str, Map.class);
+			@SuppressWarnings("unchecked")
+			Map<String,String> info = JSONObject.parseObject(str, Map.class);
 
             String[] data = new String[8];
             data[0] = this.getCountryName();

src/main/java/net/ipip/ipdb/District.java

@@ -1,5 +1,6 @@
 package net.ipip.ipdb;
 
+import java.io.Closeable;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Arrays;
@@ -14,7 +15,7 @@ public class District {
     private Reader reader;
 
     public District(String name) throws IOException,InvalidDatabaseException {
-        this.reader = new Reader(name);
+        this.reader = new RandomAccessReader(name);
     }
 
     public District(InputStream in) throws IOException, InvalidDatabaseException {
@@ -23,8 +24,11 @@ public District(InputStream in) throws IOException, InvalidDatabaseException {
 
     public boolean reload(String name) {
         try {
-            Reader r = new Reader(name);
-            this.reader = r;
+        	Reader old = this.reader;
+            this.reader = new RandomAccessReader(name);
+            if (old instanceof Closeable) {
+        		((Closeable) old).close();
+        	}
         } catch (Exception e) {
             return false;
         }

src/main/java/net/ipip/ipdb/IDC.java

@@ -1,5 +1,6 @@
 package net.ipip.ipdb;
 
+import java.io.Closeable;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Arrays;
@@ -14,7 +15,7 @@ public class IDC {
     private Reader reader;
 
     public IDC(String name) throws IOException,InvalidDatabaseException {
-        this.reader = new Reader(name);
+        this.reader = new RandomAccessReader(name);
     }
 
     public IDC(InputStream in) throws IOException, InvalidDatabaseException {
@@ -23,8 +24,11 @@ public IDC(InputStream in) throws IOException, InvalidDatabaseException {
 
     public boolean reload(String name) {
         try {
-            Reader r = new Reader(name);
-            this.reader = r;
+        	Reader old = this.reader;
+            this.reader = new RandomAccessReader(name);
+            if (old instanceof Closeable) {
+        		((Closeable) old).close();
+        	}
         } catch (Exception e) {
             return false;
         }

src/main/java/net/ipip/ipdb/IPFormatException.java

@@ -1,9 +1,12 @@
 package net.ipip.ipdb;
 
-
 public class IPFormatException extends Exception {
 
     public IPFormatException(String name) {
         super(name);
     }
+
+	public IPFormatException(Throwable cause) {
+		super(cause);
+	}
 }

src/main/java/net/ipip/ipdb/InvalidDatabaseException.java

@@ -9,4 +9,8 @@ public class InvalidDatabaseException extends IOException {
     public InvalidDatabaseException(String message) {
         super(message);
     }
+
+    public InvalidDatabaseException(Throwable cause) {
+		super(cause);
+	}
 }

src/main/java/net/ipip/ipdb/RandomAccessReader.java

@@ -0,0 +1,127 @@
+package net.ipip.ipdb;
+
+import java.io.*;
+import java.lang.reflect.Field;
+import java.nio.charset.StandardCharsets;
+
+import com.alibaba.fastjson.JSONObject;
+
+import sun.misc.Unsafe;
+
+/**
+ * @author mckuhei
+ * */
+public class RandomAccessReader extends Reader implements Closeable {
+
+	private static final Unsafe U = getUnsafe();
+	private RandomAccessFile handle;
+	private long baseOffset;
+
+	public RandomAccessReader(String file) throws IOException, InvalidDatabaseException {
+		this(new File(file));
+	}
+
+	public RandomAccessReader(File file) throws IOException, InvalidDatabaseException {
+		try {
+			this.fileSize = (int) file.length();
+			RandomAccessFile handle = this.handle = new RandomAccessFile(file, "r");
+			int metaLength = handle.readInt();
+			byte[] metaBytes = new byte[metaLength];
+			handle.readFully(metaBytes);
+
+			String metaString = new String(metaBytes);
+
+			MetaData meta = JSONObject.parseObject(metaString, MetaData.class);
+            this.nodeCount = meta.nodeCount;
+            this.meta = meta;
+
+            this.baseOffset = handle.getFilePointer();
+
+            /** for ipv4 */
+            if (0x01 == (this.meta.IPVersion & 0x01))
+            {
+                int node = 0;
+                for (int i = 0; i < 96 && node < this.nodeCount; i++) {
+                    if (i >= 80) {
+                        node = this.readNode(node, 1);
+                    } else {
+                        node = this.readNode(node, 0);
+                    }
+                }
+
+                this.v4offset = node;
+            }
+		} catch (FileNotFoundException e) {
+			throw e;
+		} catch (IOException e) {
+			throw new InvalidDatabaseException(e);
+		}
+	}
+
+	@Override
+    int readNode(int node, int index) {
+        int off = node * 8 + index * 4;
+        RandomAccessFile handle = this.handle;
+        try {
+			synchronized (handle) {
+				handle.seek(this.baseOffset + off);
+				return handle.readInt();
+			}
+		} catch (IOException e) {
+			U.throwException(e);
+		}
+        throw new InternalError("Should not reach here");
+    }
+
+	@Override
+	String resolve(int node) throws InvalidDatabaseException {
+        final int resoloved = node - this.nodeCount + this.nodeCount * 8;
+        if (resoloved >= this.fileSize) {
+            throw new InvalidDatabaseException("database resolve error");
+        }
+
+        RandomAccessFile handle = this.handle;
+
+        try {
+        	byte[] data;
+        	synchronized (handle) {
+        		handle.seek(this.baseOffset + resoloved);
+            	int size = handle.readUnsignedShort();
+
+                if (this.fileSize < (resoloved + 2 + size)) {
+                    throw new InvalidDatabaseException("database resolve error");
+                }
+
+                data = new byte[size];
+                handle.readFully(data);
+        	}
+            return new String(data, StandardCharsets.UTF_8);
+		} catch (IOException e) {
+			U.throwException(e);
+		}
+        throw new InternalError("Should not reach here");
+    }
+
+	private static Unsafe getUnsafe() {
+		try {
+			Field f = Unsafe.class.getDeclaredField("theUnsafe");
+			f.setAccessible(true);
+			return (Unsafe) f.get(null);
+		} catch (NoSuchFieldException | SecurityException | IllegalArgumentException | IllegalAccessException e) {
+			throw new InternalError("Unable to get unsafe", e);
+		}
+	}
+
+	@Override
+	protected void finalize() {
+		close();
+	}
+
+	public void close() {
+		try {
+			this.handle.close();
+		} catch (IOException e) {
+			U.throwException(e);
+		}
+	}
+}