JNI Kickstart 小結 02 ：橋接至與 Java 無關的純本地庫

時間 2019-11-24

標籤 jni kickstart 小結橋接 java 無關本地欄目 Java 简体版

原文原文鏈接

JNI 程序小結 02 ：橋接至與 Java 無關的純本地庫

Java + JNI 橋接庫 + 純本地庫異構程序構建示例。
上文： http://my.oschina.net/typhoon/blog/405527
本文爲「增強版」。

編寫 Java 程序：

[typhoon@localhost sandbox]$ ls
0_guide.txt
[typhoon@localhost sandbox]$ mkdir -p src/tfw/rsch/jni
[typhoon@localhost sandbox]$ ls
0_guide.txt src
[typhoon@localhost sandbox]$ vi src/tfw/rsch/jni/MainTest.java
[typhoon@localhost sandbox]$ vi src/tfw/rsch/jni/JniTest_01_Loader.java
[typhoon@localhost sandbox]$ vi src/tfw/rsch/jni/JniTest_01_Caller.java
[typhoon@localhost sandbox]$ vi src/tfw/rsch/jni/JniTest_02_LoadAndCall.java
[typhoon@localhost sandbox]$ vi src/tfw/rsch/jni/JniTest_03_ToPureLocal.java
[typhoon@localhost sandbox]$ ls src/tfw/rsch/jni
JniTest_01_Caller.java JniTest_01_Loader.java JniTest_02_LoadAndCall.java JniTest_03_ToPureLocal.java MainTest.java
[typhoon@localhost sandbox]$

源代碼：

src/tfw/rsch/jni/MainTest.java，啓動程序，啓動用於測試 JNI 加載與調用的函數：

/**
 * This file is a component of FREE SOFTWARE.<br />
 * <br />
 * Any entity with self-awareness, or organization are allowed to use, modify or
 * redistribute this according to the second version of "GNU Public License".<br />
 * <br />
 * The goal of this distribution is that this software being useful and helpful,
 * FOR A PARTICULAR PURPOSE.<br />
 */
package tfw.rsch.jni;

import tfw.base.util.array.ArrayToolE;
import tfw.base.util.text.TextToolE;

/**
 * Main class, to run a test method of JNI loading and calling.<br />
 *
 * @author Typhoon.Free.Wolf
 * @version 2015-06-25_18-33
 */
public class MainTest
{

	/**
	 * Main method, to run a test of JNI loading and calling.<br />
	 *
	 * @author Typhoon.Free.Wolf
	 * @version 2015-04-09_15-54
	 * @param str1dCmdArgs
	 *            - Command line arguments.<br />
	 */
	public static void main(String[] str1dCmdArgs)
	{
		new MainTest().test(str1dCmdArgs);
	}

	/**
	 * General test method.<br />
	 *
	 * @author Typhoon.Free.Wolf
	 * @version 2015-06-25_18-29
	 * @param str1dArgs
	 *            - Arguments.<br />
	 */
	private void test(String[] str1dArgs)
	{
		try
		{
			// [S] Pre-processing incoming arguments into a single string.
			String strArgText = ArrayToolE.arrayForConsole(str1dArgs);
			if (null == strArgText)
			{
				strArgText = "";
			}
			else if ("null".equals(strArgText))
			{
				strArgText = null;
			}
			// [E] Pre-processing incoming arguments into a single string.

			test_01();
			test_02(strArgText);
			test_03(strArgText);
		}
		catch (Throwable t)
		{
			t.printStackTrace();
		}
	}

	/**
	 * Test 01: Basic loading and calling of the native library.<br />
	 *
	 * @author Typhoon.Free.Wolf
	 * @version 2015-05-26_16-26
	 */
	private void test_01()
	{
		// Loading native library.
		new JniTest_01_Loader();

		// Calling native method of native library.
		JniTest_01_Caller jt_01 = new JniTest_01_Caller();
		jt_01.println();
		jt_01.nativePrintln();
	}

	/**
	 * Test 02: <strong>Argument</strong> passing in and <strong>return
	 * value</strong> retrieving.<br />
	 *
	 * @author Typhoon.Free.Wolf
	 * @version 2015-06-25_18-29
	 * @param strArgText
	 *            - Text argument to the native library.<br />
	 */
	private void test_02(String strArgText)
	{
		// Loading native library during class initializing.
		JniTest_02_LoadAndCall jt_02 = new JniTest_02_LoadAndCall();

		{
			String strMethodHead =
					TextToolE.concat("\tpublic String jt_02.javaManipulate(",
							((null == strArgText) ? "null"
									: ("\"" + strArgText + "\"")) + ")\n\t{");
			System.out.println(strMethodHead);

			// Calling the java method.
			String strRst = jt_02.javaManipulate(strArgText);

			String strMethodTail =
					TextToolE
							.concat("\t}\n\tGot Return Value: ",
									((null == strRst) ? "null"
											: ("\"" + strRst + "\"")));
			System.out.println(strMethodTail);
		}

		System.out.println();

		{
			String strMethodHead =
					TextToolE.concat(
							"\tpublic native String jt_02.nativeManipulate(",
							((null == strArgText) ? "null"
									: ("\"" + strArgText + "\"")) + ")\n\t{");
			System.out.println(strMethodHead);

			// Calling the native method, here!
			String strOut = jt_02.nativeManipulate(strArgText);

			String strMethodTail =
					TextToolE
							.concat("\t}\n\tGot Return Value: ",
									((null == strOut) ? "null"
											: ("\"" + strOut + "\"")));
			System.out.println(strMethodTail);
		}
	}

	/**
	 * Test 03: Calling to the <u><strong>pure local native library</strong>
	 * that without any relationship to JNI or java</u> through the
	 * <u><strong>native JNI-bridge library</strong></u>.<br />
	 *
	 * @author Typhoon.Free.Wolf
	 * @version 2015-06-25_18-29
	 * @param strArgText
	 *            - Text argument to the native library.<br />
	 */
	private void test_03(String strArgText)
	{
		// Loading native library during class initializing.
		JniTest_03_ToPureLocal jt_03 = new JniTest_03_ToPureLocal();

		{
			String strMethodHead =
					TextToolE.concat("\tpublic String jt_03.javaManipulate(",
							((null == strArgText) ? "null"
									: ("\"" + strArgText + "\"")) + ")\n\t{");
			System.out.println(strMethodHead);

			// Calling the java method.
			String strRst = jt_03.javaManipulate(strArgText);

			String strMethodTail =
					TextToolE
							.concat("\t}\n\tGot Return Value: ",
									((null == strRst) ? "null"
											: ("\"" + strRst + "\"")));
			System.out.println(strMethodTail);
		}

		System.out.println();

		{
			String strMethodHead =
					TextToolE.concat(
							"\tpublic native String jt_03.nativeManipulate(",
							((null == strArgText) ? "null"
									: ("\"" + strArgText + "\"")) + ")\n\t{");
			System.out.println(strMethodHead);

			// Calling the native method, here!
			String strOut = jt_03.nativeManipulate(strArgText);

			String strMethodTail =
					TextToolE
							.concat("\t}\n\tGot Return Value: ",
									((null == strOut) ? "null"
											: ("\"" + strOut + "\"")));
			System.out.println(strMethodTail);
		}
	}

}

src/tfw/rsch/jni/JniTest_01_Loader.java，示例 01 - JNI 本地庫加載：

/**
 * This file is a component of FREE SOFTWARE.<br />
 * <br />
 * Any entity with self-awareness, or organization are allowed to use, modify or
 * redistribute this according to the second version of "GNU Public License".<br />
 * <br />
 * The goal of this distribution is that this software being useful and helpful,
 * FOR A PARTICULAR PURPOSE.<br />
 */
package tfw.rsch.jni;

/**
 * Test 01:<br />
 * This class loads the native library (shared object, or dynamic link library,
 * and so on) during class initializing.<br />
 *
 * @author Typhoon.Free.Wolf
 * @version 2015-05-26_16-30
 */
public class JniTest_01_Loader
{

	/**
	 * Make sure to run during class initializing.<br />
	 */
	static
	{
		loadNativeLibrary();
	}

	/**
	 * Loads the native library (shared object, or dynamic link library, and so
	 * on).<br />
	 *
	 * @author Typhoon.Free.Wolf
	 * @version 2015-05-26_15-56
	 */
	private static void loadNativeLibrary()
	{
		// Loading native library file "libJniTest_01_ThisNameIsOK.so" (or
		// "JniTest_01_ThisNameIsOK.dll", and so on) according to the library
		// name "JniTest_01_ThisNameIsOK".
		String strNativeLibraryName = "JniTest_01_AnyNameIsOK";
		System.out.println("Loading \"" + strNativeLibraryName + "\"...");
		System.loadLibrary(strNativeLibraryName); // <== Loading, here!
		System.out.println("Loaded.");
	}

}

src/tfw/rsch/jni/JniTest_01_Caller.java，示例 01 - JNI 本地庫調用：

/**
 * This file is a component of FREE SOFTWARE.<br />
 * <br />
 * Any entity with self-awareness, or organization are allowed to use, modify or
 * redistribute this according to the second version of "GNU Public License".<br />
 * <br />
 * The goal of this distribution is that this software being useful and helpful,
 * FOR A PARTICULAR PURPOSE.<br />
 */
package tfw.rsch.jni;

/**
 * Test 01:<br />
 * This class provides an entrance to the native method in the native library
 * (shared object, or dynamic link library, and so on) for java calling.<br />
 *
 * @author Typhoon.Free.Wolf
 * @version 2015-05-26_16-30
 */
public class JniTest_01_Caller
{

	/**
	 * A java method, prints a message to the standard-out.<br />
	 *
	 * @author Typhoon.Free.Wolf
	 * @version 2015-04-11_14-09
	 */
	public void println()
	{
		System.out.println("\tJava:\tWorks!");
	}

	/**
	 * Entrance to the native method in the native library (shared object, or
	 * dynamic link library, and so on).<br />
	 * The corresponding native method is supposed to print a message to the
	 * standard-out, just like what the java one above does.<br />
	 *
	 * @author Typhoon.Free.Wolf
	 * @version 2015-04-11_14-09
	 */
	public native void nativePrintln();

}

src/tfw/rsch/jni/JniTest_02_LoadAndCall.java，示例 02 - 加載和調用 JNI 本地庫，進行控制檯 IO 操做：

/**
 * This file is a component of FREE SOFTWARE.<br />
 * <br />
 * Any entity with self-awareness, or organization are allowed to use, modify or
 * redistribute this according to the second version of "GNU Public License".<br />
 * <br />
 * The goal of this distribution is that this software being useful and helpful,
 * FOR A PARTICULAR PURPOSE.<br />
 */
package tfw.rsch.jni;

import tfw.base.util.misc.MiscToolE;
import tfw.base.util.text.TextToolE;

/**
 * Test 02: This class<br />
 * <ul>
 * <li>Loads the native library (shared object, or dynamic link library, and so
 * on) during class initializing;<br />
 * </li>
 * <li>Provides an entrance to the native method in the native library.<br />
 * </li>
 * </ul>
 *
 * @author Typhoon.Free.Wolf
 * @version 2015-06-25_18-38
 */
public class JniTest_02_LoadAndCall
{

	/**
	 * Make sure to run during class initializing.<br />
	 */
	static
	{
		loadNativeLibrary();
	}

	/**
	 * Loads the native library (shared object, or dynamic link library, and so
	 * on).<br />
	 *
	 * @author Typhoon.Free.Wolf
	 * @version 2015-05-26_15-58
	 */
	private static void loadNativeLibrary()
	{
		// Loading native library file "libJniTest_02.so" (or "JniTest_02.dll",
		// and so on) according to the library name "JniTest_02".
		String strNativeLibraryName = "JniTest_02";
		System.out.println("Loading \"" + strNativeLibraryName + "\"...");
		System.loadLibrary(strNativeLibraryName); // <== Loading, here!
		System.out.println("Loaded.");
	}

	/**
	 * A java method.<br />
	 * Prints the incoming text string to the standard-out, then receives the
	 * text string from the standard-input and finally returns it.<br />
	 *
	 * @author Typhoon.Free.Wolf
	 * @version 2015-06-25_18-36
	 * @param strText
	 *            - Incoming text string.<br />
	 * @return A text string from the standard-input, <strong>could be
	 *         null.</strong><br />
	 */
	public String javaManipulate(String strText)
	{
		// Printing the received argument.
		String strReceiveText =
				TextToolE.concat("\t\tJava:\n\n\t\tArgument:\n\t\t\t",
						(null == strText) ? "null" : ("\"" + strText + "\""));
		System.out.println(strReceiveText);

		// [S] Receiving a text string for standard input.
		System.out
				.print("\t\tUser Input (\"null\" would be considered as null):\n\t\t\t");
		String strUserInputText = MiscToolE.getline(System.in);
		System.out.println("\t\tUser Input Received:\n\t\t\t"
				+ ((null == strUserInputText) ? "null" : ("\""
						+ strUserInputText + "\"")));
		// [E] Receiving a text string for standard input.

		// [S] Printing the value which to be returned.
		String strReturnValue =
				"null".equals(strUserInputText) ? null : strUserInputText;
		System.out.println("\t\tReturns:\n\t\t\t"
				+ ((null == strReturnValue) ? "null"
						: ("\"" + strReturnValue + "\"")));
		// [E] Printing the value which to be returned.

		// Returning.
		return strReturnValue;
	}

	/**
	 * Entrance to the native method in the native library (shared object, or
	 * dynamic link library, and so on).<br />
	 * The corresponding native method is supposed to print the incoming text
	 * string to the standard-out, then receive the text string from the
	 * standard-input and finally return it, just like what the java one above
	 * does.<br />
	 *
	 * @author Typhoon.Free.Wolf
	 * @version 2015-04-11_14-10
	 * @param strText
	 *            - Incoming text string.<br />
	 * @return A text string actually returned from the native method,
	 *         <strong>could be null.</strong><br />
	 */
	public native String nativeManipulate(String strText);

}

src/tfw/rsch/jni/JniTest_03_ToPureLocal.java，示例 03 - 經過加載和調用 JNI 本地庫進一步調用一個與 Java 無關的純本地庫，進行控制檯 IO 操做：

/**
 * This file is a component of FREE SOFTWARE.<br />
 * <br />
 * Any entity with self-awareness, or organization are allowed to use, modify or
 * redistribute this according to the second version of "GNU Public License".<br />
 * <br />
 * The goal of this distribution is that this software being useful and helpful,
 * FOR A PARTICULAR PURPOSE.<br />
 */
package tfw.rsch.jni;

import tfw.base.util.misc.MiscToolE;
import tfw.base.util.text.TextToolE;

/**
 * Test 03: This class<br />
 * <ul>
 * <li>Loads the native library (shared object, or dynamic link library, and so
 * on) during class initializing;<br />
 * </li>
 * <li>Provides an entrance to the native method in the <strong><u>native
 * JNI-bridge library</u></strong>.<br />
 * </li>
 * <li>The <u><strong>native JNI-bridge library</strong></u> is to call another
 * <u><strong>pure, local native library</strong> that without any relationship
 * to JNI or java</u>.<br />
 * </li>
 * </ul>
 *
 * @author Typhoon.Free.Wolf
 * @version 2015-06-25_18-40
 */
public class JniTest_03_ToPureLocal
{

	/**
	 * Make sure to run during class initializing.<br />
	 */
	static
	{
		loadNativeLibrary();
	}

	/**
	 * Loads the native library (shared object, or dynamic link library, and so
	 * on).<br />
	 *
	 * @author Typhoon.Free.Wolf
	 * @version 2015-05-26_15-58
	 */
	private static void loadNativeLibrary()
	{
		// Loading native library file "libJniTest_03.so" (or "JniTest_03.dll",
		// and so on) according to the library name "JniTest_03".
		String strNativeLibraryName = "JniTest_03";
		System.out.println("Loading \"" + strNativeLibraryName + "\"...");
		System.loadLibrary(strNativeLibraryName); // <== Loading, here!
		System.out.println("Loaded.");
	}

	/**
	 * A java method.<br />
	 * Prints the incoming text string to the standard-out, then receives the
	 * text string from the standard-input and finally returns it.<br />
	 *
	 * @author Typhoon.Free.Wolf
	 * @version 2015-06-25_18-36
	 * @param strText
	 *            - Incoming text string.<br />
	 * @return A text string from the standard-input, <strong>could be
	 *         null.</strong><br />
	 */
	public String javaManipulate(String strText)
	{
		// Printing the received argument.
		String strReceiveText =
				TextToolE.concat("\t\tJava:\n\n\t\tArgument:\n\t\t\t",
						(null == strText) ? "null" : ("\"" + strText + "\""));
		System.out.println(strReceiveText);

		// [S] Receiving a text string for standard input.
		System.out
				.print("\t\tUser Input (\"null\" would be considered as null):\n\t\t\t");
		String strUserInputText = MiscToolE.getline(System.in);
		System.out.println("\t\tUser Input Received:\n\t\t\t"
				+ ((null == strUserInputText) ? "null" : ("\""
						+ strUserInputText + "\"")));
		// [E] Receiving a text string for standard input.

		// [S] Printing the value which to be returned.
		String strReturnValue =
				"null".equals(strUserInputText) ? null : strUserInputText;
		System.out.println("\t\tReturns:\n\t\t\t"
				+ ((null == strReturnValue) ? "null"
						: ("\"" + strReturnValue + "\"")));
		// [E] Printing the value which to be returned.

		// Returning.
		return strReturnValue;
	}

	/**
	 * Entrance to the native method in the native library (shared object, or
	 * dynamic link library, and so on).<br />
	 * The corresponding native method is supposed to print the incoming text
	 * string to the standard-out, then receive the text string from the
	 * standard-input and finally return it, just like what the java one above
	 * does.<br />
	 *
	 * @author Typhoon.Free.Wolf
	 * @version 2015-04-11_14-10
	 * @param strText
	 *            - Incoming text string.<br />
	 * @return A text string actually returned from the native method,
	 *         <strong>could be null.</strong><br />
	 */
	public native String nativeManipulate(String strText);

}

編譯 Java 程序：

[typhoon@localhost sandbox]$ cp -a ../lib .
[typhoon@localhost sandbox]$ mkdir classes
[typhoon@localhost sandbox]$ ls
0_guide.txt classes lib src
[typhoon@localhost sandbox]$ ls lib # ← 上述源代碼引用的工具類在這個文件夾裏。
tfw-base.aij.jar tfw-base.v2.2.8_2014-12-22_22-00.longest_night.jre150.aij.jar
# ↑ ↖_ 工具類「ArrayToolE」、「MiscToolE」和「TextToolE」所在。
# `- 指向「tfw-base.v2.2.8_2014-12-22_22-00.longest_night.jre150.aij.jar」的符號連接。
[typhoon@localhost sandbox]$ javac -classpath lib/tfw-base.aij.jar -d classes src/tfw/rsch/jni/*.java
[typhoon@localhost sandbox]$ ls classes/tfw/rsch/jni
JniTest_01_Caller.class JniTest_01_Loader.class JniTest_02_LoadAndCall.class JniTest_03_ToPureLocal.class MainTest.class
[typhoon@localhost sandbox]$

生成 JNI 頭文件：

[typhoon@localhost sandbox]$ vi build_jni.sh
[typhoon@localhost sandbox]$ ls
0_guide.txt build_jni.sh classes lib src
[typhoon@localhost sandbox]$ sh build_jni.sh
javah -classpath classes -o c_include/JniTest_01_Any_name_is_OK.h tfw.rsch.jni.JniTest_01_Caller;echo $?;
0
javah -classpath classes -o c_include/JniTest_02.h tfw.rsch.jni.JniTest_02_LoadAndCall;echo $?;
0
javah -classpath classes -o c_include/JniTest_03.h tfw.rsch.jni.JniTest_03_ToPureLocal;echo $?;
0
[typhoon@localhost sandbox]$ ls
0_guide.txt build_jni.sh c_include classes lib src
[typhoon@localhost sandbox]$ ls c_include
JniTest_01_Any_name_is_OK.h JniTest_02.h JniTest_03.h
[typhoon@localhost sandbox]$

腳本 build_jni.sh 內容：

#!/bin/sh

# JNI head file generating:
CLAZZ="tfw.rsch.jni.JniTest_01_Caller";
OUTPUT="c_include/JniTest_01_Any_name_is_OK.h";
echo "javah -classpath classes -o $OUTPUT $CLAZZ;echo \$?;";
javah -classpath classes -o $OUTPUT $CLAZZ;echo $?;

CLAZZ="tfw.rsch.jni.JniTest_02_LoadAndCall";
OUTPUT="c_include/JniTest_02.h";
echo "javah -classpath classes -o $OUTPUT $CLAZZ;echo \$?;";
javah -classpath classes -o $OUTPUT $CLAZZ;echo $?;

CLAZZ="tfw.rsch.jni.JniTest_03_ToPureLocal";
OUTPUT="c_include/JniTest_03.h";
echo "javah -classpath classes -o $OUTPUT $CLAZZ;echo \$?;";
javah -classpath classes -o $OUTPUT $CLAZZ;echo $?;

頭文件源代碼：

c_include/JniTest_01_Any_name_is_OK.h，示例 01 對應的頭文件：

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class tfw_rsch_jni_JniTest_01_Caller */

#ifndef _Included_tfw_rsch_jni_JniTest_01_Caller
#define _Included_tfw_rsch_jni_JniTest_01_Caller
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     tfw_rsch_jni_JniTest_01_Caller
 * Method:    nativePrintln
 * Signature: ()V
 */
JNIEXPORT void JNICALL Java_tfw_rsch_jni_JniTest_101_1Caller_nativePrintln
  (JNIEnv *, jobject);

#ifdef __cplusplus
}
#endif
#endif

c_include/JniTest_02.h，示例 02 對應的頭文件：

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class tfw_rsch_jni_JniTest_02_LoadAndCall */

#ifndef _Included_tfw_rsch_jni_JniTest_02_LoadAndCall
#define _Included_tfw_rsch_jni_JniTest_02_LoadAndCall
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     tfw_rsch_jni_JniTest_02_LoadAndCall
 * Method:    nativeManipulate
 * Signature: (Ljava/lang/String;)Ljava/lang/String;
 */
JNIEXPORT jstring JNICALL Java_tfw_rsch_jni_JniTest_102_1LoadAndCall_nativeManipulate
  (JNIEnv *, jobject, jstring);

#ifdef __cplusplus
}
#endif
#endif

c_include/JniTest_03.h，示例 03 對應的頭文件：

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class tfw_rsch_jni_JniTest_03_ToPureLocal */

#ifndef _Included_tfw_rsch_jni_JniTest_03_ToPureLocal
#define _Included_tfw_rsch_jni_JniTest_03_ToPureLocal
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     tfw_rsch_jni_JniTest_03_ToPureLocal
 * Method:    nativeManipulate
 * Signature: (Ljava/lang/String;)Ljava/lang/String;
 */
JNIEXPORT jstring JNICALL Java_tfw_rsch_jni_JniTest_103_1ToPureLocal_nativeManipulate
  (JNIEnv *, jobject, jstring);

#ifdef __cplusplus
}
#endif
#endif

編寫本地庫程序：

[typhoon@localhost sandbox]$ mkdir c_src
[typhoon@localhost sandbox]$ ls
0_guide.txt build_jni.sh c_include classes c_src lib src
[typhoon@localhost sandbox]$ vi c_src/JniTest_01_ANY_NAME_IS_OK.c
[typhoon@localhost sandbox]$ vi c_src/JniTest_02.c
[typhoon@localhost sandbox]$ vi c_src/JniTest_03.c
[typhoon@localhost sandbox]$ vi c_src/PureLocalNoJava.c
[typhoon@localhost sandbox]$ ls c_src
JniTest_01_ANY_NAME_IS_OK.c JniTest_02.c JniTest_03.c PureLocalNoJava.c
[typhoon@localhost sandbox]$

源代碼：

c_src/JniTest_01_ANY_NAME_IS_OK.c，示例 01 將要調用的 JNI 本地庫的源代碼；僅僅打印文字以證實被調用了：

#include <jni.h>
#include <stdio.h>
#include <JniTest_01_Any_name_is_OK.h>

JNIEXPORT void JNICALL Java_tfw_rsch_jni_JniTest_101_1Caller_nativePrintln
		(JNIEnv *env, jobject obj)
{
	printf("\tJNI:\tWorks!\n");
	return;
}

c_src/JniTest_02.c，示例 02 將要調用的 JNI 本地庫的源代碼；打印傳入的參數、從控制檯獲取輸入並打印和返回此輸入：

#include <jni.h>
#include <stdio.h>
#include <JniTest_02.h>

void interactiveGetLine(char *strBuff, int intBuffSize)
{
	printf("\t\tvoid interactiveGetLine(char *strBuff, int [%d])\n\t\t{\n",
			intBuffSize);

	// Receiving a text string for standard input, without line breaker.
	printf("\t\t\tUser Input:\n\t\t\t\t");
	fgets(strBuff, intBuffSize, stdin);
	printf("\t\t\tUser Input Received:\n\t\t\t\t\"%s\"\n", strBuff);

	// [S] Setting the value index of first line breaker as string ending.
	int intIdx = 0;
	for (; intIdx < intBuffSize; intIdx++)
	{
		if ('\r' == strBuff[intIdx] || '\n' == strBuff[intIdx])
		{
			strBuff[intIdx] = '\0';
			break;
		}
	}
	printf("\t\t\tLine Breaker Removed:\n\t\t\t\t\"%s\"\n", strBuff);
	// [E] Setting the value index of first line breaker as string ending.

	printf("\t\t}\n");
}

JNIEXPORT jstring JNICALL Java_tfw_rsch_jni_JniTest_102_1LoadAndCall_nativeManipulate
		(JNIEnv *jniEnv, jobject jobj, jstring jstrArg)
{
	// Printing the received argument.
	printf("\t\tJNI:\n\n\t\tOriginal Argument:\n\t\t\t");
	printf((NULL == jstrArg) ? "%s\n" : "\"%s\"\n", jstrArg);

	// Converting the received argument into a C styled string, and printing.
	const char *strConvertedArg = (NULL == jstrArg) ? NULL
			: (*jniEnv)->GetStringUTFChars(jniEnv, jstrArg, 0);
	printf("\t\tConverted Argument:\n\t\t\t");
	printf((NULL == strConvertedArg) ? "%s\n" : "\"%s\"\n", strConvertedArg);

	// Now the JNI argument is useless, release it.
	(*jniEnv)->ReleaseStringUTFChars(jniEnv, jstrArg, strConvertedArg);

	// Receiving a line of user input from standard input into buffer.
	int MEANINGFUL_LENGTH = 256;
	int intBuffSize = MEANINGFUL_LENGTH + 1;
	char ch1dUserInputBuff[intBuffSize];
	interactiveGetLine(ch1dUserInputBuff, intBuffSize);

	// Printing the value which to be returned.
	printf("\t\tReturn Value (\"NULL\" is considered as null):\n\t\t\t");
	const char *strToReturn = (0 == strcmp(ch1dUserInputBuff, "NULL")) ? NULL
			: ch1dUserInputBuff;
	printf((NULL == strToReturn) ? "%s\n" : "\"%s\"\n", strToReturn);

	// Converting the return value into java string, and printing.
	jstring jstrToReturn = (*jniEnv)->NewStringUTF(jniEnv, strToReturn);
	printf("\t\tConverted:\n\t\t\t");
	printf((NULL == jstrToReturn) ? "%s\n" : "\"%s\"\n", jstrToReturn);

	// Returning.
	return jstrToReturn;
}

c_src/JniTest_03.c，示例 03 將要調用的 JNI 本地庫的源代碼；打印傳入的參數；調用一個純本地庫以從控制檯獲取輸入；打印並返回此輸入：

#include <jni.h>
#include <stdio.h>
#include <JniTest_03.h>

void checkString(char *strSrc, int intStartIdx, int intCheckCount)
{
	int intIdx;
	int intFinalIdx = intStartIdx + intCheckCount;

	if (1 > intCheckCount)
	{
		printf("\nCheck count: %d  From index %d  Final index limit: %d.\nIndex:",
			intCheckCount, intStartIdx, intFinalIdx - 1);
	}

	printf("\nCheck count: [%d]  From index [%d] to [%d]\nIndex:", intCheckCount,
			intStartIdx, intFinalIdx - 1);
	for (intIdx = 0; intIdx < intCheckCount; intIdx++)
	{
		printf("\t[%d]", intIdx);
	}
	printf("\nASCII:");
	for (intIdx = 0; intIdx < intFinalIdx; intIdx++)
	{
		printf("\t[%d]", strSrc[intIdx]);
	}
	printf("\nChar:");
	for (intIdx = 0; intIdx < intFinalIdx; intIdx++)
	{
		if ('\n' == strSrc[intIdx])
		{
			printf("\t[\\n]");
		}
		else
		{
			printf("\t[%c]", strSrc[intIdx]);
		}
	}
	printf("\n");
}

void interactiveGetLine(char *strBuff, int intBuffSize)
{
	printf("\t\tvoid interactiveGetLine(char *strBuff, int [%d])\n\t\t{\n",
			intBuffSize);
	printf("\t\t\tPure Local: Look Ma No Java!\n\n");

	// Receiving a text string for standard input, without line breaker.
	printf("\t\t\tUser Input:\n\t\t\t\t");
	fgets(strBuff, intBuffSize, stdin);
	printf("\t\t\tUser Input Received:\n\t\t\t\t\"%s\"\n", strBuff);

	// [S] Setting the value index of first line breaker as string ending.
	int intIdx = 0;
	for (; intIdx < intBuffSize; intIdx++)
	{
		if ('\r' == strBuff[intIdx] || '\n' == strBuff[intIdx])
		{
			strBuff[intIdx] = '\0';
			break;
		}
	}
	printf("\t\t\tLine Breaker Removed:\n\t\t\t\t\"%s\"\n", strBuff);
	// [E] Setting the value index of first line breaker as string ending.

	printf("\t\t}\n");
}

JNIEXPORT jstring JNICALL Java_tfw_rsch_jni_JniTest_103_1ToPureLocal_nativeManipulate
		(JNIEnv *jniEnv, jobject jobj, jstring jstrArg)
{
	// Printing the received argument.
	printf("\t\tJNI:\n\n\t\tOriginal Argument:\n\t\t\t");
	printf((NULL == jstrArg) ? "%s\n" : "\"%s\"\n", jstrArg);

	// Converting the received argument into a C styled string, and printing.
	const char *strConvertedArg = (NULL == jstrArg) ? NULL
			: (*jniEnv)->GetStringUTFChars(jniEnv, jstrArg, 0);
	printf("\t\tConverted Argument:\n\t\t\t");
	printf((NULL == strConvertedArg) ? "%s\n" : "\"%s\"\n", strConvertedArg);

	// Now the JNI argument is useless, release it.
	(*jniEnv)->ReleaseStringUTFChars(jniEnv, jstrArg, strConvertedArg);

	// Receiving a line of user input from standard input into buffer.
	int MEANINGFUL_LENGTH = 256;
	int intBuffSize = MEANINGFUL_LENGTH + 1;
	char ch1dUserInputBuff[intBuffSize];
	interactiveGetLine(ch1dUserInputBuff, intBuffSize);

	// Printing the value which to be returned.
	printf("\t\tReturn Value (\"NULL\" is considered as null):\n\t\t\t");
	const char *strToReturn = (0 == strcmp(ch1dUserInputBuff, "NULL")) ? NULL
			: ch1dUserInputBuff;
	printf((NULL == strToReturn) ? "%s\n" : "\"%s\"\n", strToReturn);

	// Converting the return value into java string, and printing.
	jstring jstrToReturn = (*jniEnv)->NewStringUTF(jniEnv, strToReturn);
	printf("\t\tConverted:\n\t\t\t");
	printf((NULL == jstrToReturn) ? "%s\n" : "\"%s\"\n", jstrToReturn);

	// Returning.
	return jstrToReturn;
}

c_src/PureLocalNoJava.c，示例 03 將要經過 JNI 本地庫橋接調用的、和 Java 徹底無關的純本地庫的源代碼；從控制檯獲取輸入，打印並返回：

#include <stdio.h>

void interactiveGetLine(char *strBuff, int intBuffSize)
{
	printf("\t\tvoid interactiveGetLine(char *strBuff, int [%d])\n\t\t{\n",
			intBuffSize);
	printf("\t\t\tPure Local:\n\n");

	// Receiving a text string for standard input, without line breaker.
	printf("\t\t\tUser Input:\n\t\t\t\t");
	fgets(strBuff, intBuffSize, stdin);
	printf("\t\t\tUser Input Received:\n\t\t\t\t\"%s\"\n", strBuff);

	// [S] Setting the value index of first line breaker as string ending.
	int intIdx = 0;
	for (; intIdx < intBuffSize; intIdx++)
	{
		if ('\r' == strBuff[intIdx] || '\n' == strBuff[intIdx])
		{
			strBuff[intIdx] = '\0';
			break;
		}
	}
	printf("\t\t\tLine Breaker Removed:\n\t\t\t\t\"%s\"\n", strBuff);
	// [E] Setting the value index of first line breaker as string ending.

	printf("\t\t}\n");
}

編譯本地庫：

[typhoon@localhost sandbox]$ vi build_native.sh
[typhoon@localhost sandbox]$ ls
0_guide.txt build_jni.sh build_native.sh c_include classes c_src lib src
[typhoon@localhost sandbox]$ sh build_native.sh
gcc c_src/JniTest_01_ANY_NAME_IS_OK.c -fPIC -shared -I c_include -I /usr/lib/jvm/java-1.7.0-openjdk.x86_64/include -I /usr/lib/jvm/java-1.7.0-openjdk.x86_64/include/linux -o lib/libJniTest_01_AnyNameIsOK.so;echo $?;
0
gcc c_src/JniTest_02.c -fPIC -shared -I c_include -I /usr/lib/jvm/java-1.7.0-openjdk.x86_64/include -I /usr/lib/jvm/java-1.7.0-openjdk.x86_64/include/linux -o lib/libJniTest_02.so;echo $?;
0
gcc c_src/PureLocalNoJava.c -fPIC -shared -o lib/libPureLocalNoJava.so;echo $?;
0
gcc c_src/JniTest_03.c -fPIC -shared -I c_include -I /usr/lib/jvm/java-1.7.0-openjdk.x86_64/include -I /usr/lib/jvm/java-1.7.0-openjdk.x86_64/include/linux -L /ext/var/home.123/typhoon/work/Eclipse.Projects/java.tfw.jni_rsch/sandbox/lib -l PureLocalNoJava -o lib/libJniTest_03.so;echo $?;
0
chmod 644 lib/*.so;echo $?;
0
[typhoon@localhost sandbox]$ ls lib
libJniTest_01_AnyNameIsOK.so libJniTest_02.so libJniTest_03.so libPureLocalNoJava.so tfw-base.aij.jar tfw-base.v2.2.8_2014-12-22_22-00.longest_night.jre150.aij.jar
[typhoon@localhost sandbox]$

腳本 build_native.sh 內容：

#!/bin/sh

# Native library compiling:
# JNI related:
C_SOURCE_FILE="c_src/JniTest_01_ANY_NAME_IS_OK.c";
OUTPUT="lib/libJniTest_01_AnyNameIsOK.so";
echo "gcc $C_SOURCE_FILE -fPIC -shared -I c_include -I $JAVA_HOME/include -I $JAVA_HOME/include/linux $3 -o $OUTPUT;echo \$?;";
gcc $C_SOURCE_FILE -fPIC -shared -I c_include -I $JAVA_HOME/include -I $JAVA_HOME/include/linux $3 -o $OUTPUT;echo $?;

# JNI related:
C_SOURCE_FILE="c_src/JniTest_02.c";
OUTPUT="lib/libJniTest_02.so";
echo "gcc $C_SOURCE_FILE -fPIC -shared -I c_include -I $JAVA_HOME/include -I $JAVA_HOME/include/linux $3 -o $OUTPUT;echo \$?;";
gcc $C_SOURCE_FILE -fPIC -shared -I c_include -I $JAVA_HOME/include -I $JAVA_HOME/include/linux $3 -o $OUTPUT;echo $?;

# Pure local:
C_SOURCE_FILE="c_src/PureLocalNoJava.c";
OUTPUT="lib/libPureLocalNoJava.so";
echo "gcc $C_SOURCE_FILE -fPIC -shared -o $OUTPUT;echo \$?;";
gcc $C_SOURCE_FILE -fPIC -shared -o $OUTPUT;echo $?;

# JNI related:
C_SOURCE_FILE="c_src/JniTest_03.c";
OUTPUT="lib/libJniTest_03.so";
LIB_PATH="$(pwd)/lib";
LIB_NAME="PureLocalNoJava";
echo "gcc $C_SOURCE_FILE -fPIC -shared -I c_include -I $JAVA_HOME/include -I $JAVA_HOME/include/linux -L $LIB_PATH -l $LIB_NAME -o $OUTPUT;echo \$?;";
gcc $C_SOURCE_FILE -fPIC -shared -I c_include -I $JAVA_HOME/include -I $JAVA_HOME/include/linux -L $LIB_PATH -l $LIB_NAME -o $OUTPUT;echo $?;

# Permission:
echo "chmod 644 lib/*.so;echo \$?;";
chmod 644 lib/*.so;echo $?;

運行準備與檢查：

[typhoon@localhost sandbox]$ alias jrun='java -classpath classes:lib/tfw-base.aij.jar -Djava.library.path=lib'
[typhoon@localhost sandbox]$ export LD_LIBRARY_PATH=LD_LIBRARY_PATH:$(pwd)/lib
[typhoon@localhost sandbox]$ echo $LD_LIBRARY_PATH
LD_LIBRARY_PATH:/home/typhoon/123/work/Eclipse.Projects/java.tfw.jni_rsch/sandbox/lib
[typhoon@localhost sandbox]$ ldd lib/libJniTest_03.so
ldd: 警告: 你沒有執行權限 `lib/libJniTest_03.so'
linux-vdso.so.1 => (0x00007ffff51e5000)
libPureLocalNoJava.so => /home/typhoon/123/work/Eclipse.Projects/java.tfw.jni_rsch/sandbox/lib/libPureLocalNoJava.so (0x00007fc9d0cb9000)
libc.so.6 => /lib64/libc.so.6 (0x00007fc9d090d000)
/lib64/ld-linux-x86-64.so.2 (0x0000003132400000)
[typhoon@localhost sandbox]$

運行：

[typhoon@localhost sandbox]$ jrun tfw.rsch.jni.MainTest "一二三四五" "上山打老虎" Loading "JniTest_01_AnyNameIsOK"... Loaded. Java: Works! JNI: Works! Loading "JniTest_02"... Loaded. public String jt_02.javaManipulate("一二三四五, 上山打老虎") { Java: Argument: "一二三四五, 上山打老虎" User Input ("null" would be considered as null): 老虎沒打到，打到小松鼠！ User Input Received: "老虎沒打到，打到小松鼠！" Returns: "老虎沒打到，打到小松鼠！" } Got Return Value: "老虎沒打到，打到小松鼠！" public native String jt_02.nativeManipulate("一二三四五, 上山打老虎") { JNI: Original Argument: " 4��" Converted Argument: "一二三四五, 上山打老虎" void interactiveGetLine(char *strBuff, int [257]) { User Input: NULL User Input Received: "NULL " Line Breaker Removed: "NULL" } Return Value ("NULL" is considered as null): (null) Converted: (null) } Got Return Value: null Loading "JniTest_03"... Loaded. public String jt_03.javaManipulate("一二三四五, 上山打老虎") { Java: Argument: "一二三四五, 上山打老虎" User Input ("null" would be considered as null): null User Input Received: "null" Returns: null } Got Return Value: null public native String jt_03.nativeManipulate("一二三四五, 上山打老虎") { JNI: Original Argument: " 4��" Converted Argument: "一二三四五, 上山打老虎" void interactiveGetLine(char *strBuff, int [257]) { Pure Local: Look Ma No Java! User Input: 老虎沒打到，打到小松鼠！ User Input Received: "老虎沒打到，打到小松鼠！ " Line Breaker Removed: "老虎沒打到，打到小松鼠！" } Return Value ("NULL" is considered as null): "老虎沒打到，打到小松鼠！" Converted: "h��" } Got Return Value: "老虎沒打到，打到小松鼠！" [typhoon@localhost sandbox]$