JNI 返回字符串数据

• D_string.java 文件

package com.ldq.d_string;

public class D_string {
    static {
        System.loadLibrary("Case");
    }

    public native String getCase(String string);

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        D_string d = new D_string();
        String s = "heLLo";
        System.out.println("before change: " + s);
        System.out.println("after change: " + d.getCase(s));
    }

}

package com.ldq.d_string; public class D_string { static { System.loadLibrary("Case"); } public native String getCase(String string); /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub D_string d = new D_string(); String s = "heLLo"; System.out.println("before change: " + s); System.out.println("after change: " + d.getCase(s)); } }

 

• javah -jni com.ldq.d_string.D_string 生成文件 com_ldq_d_string_D_string.h

/* DO NOT EDIT THIS FILE - it is machine generated */
#include
/* Header for class com_ldq_d_string_D_string */

#ifndef _Included_com_ldq_d_string_D_string
#define _Included_com_ldq_d_string_D_string
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     com_ldq_d_string_D_string
 * Method:    getCase
 * Signature: (Ljava/lang/String;)Ljava/lang/String;
 */
JNIEXPORT jstring JNICALL Java_com_ldq_d_1string_D_1string_getCase
  (JNIEnv *, jobject, jstring);

#ifdef __cplusplus
}
#endif
#endif

/* DO NOT EDIT THIS FILE - it is machine generated */ #include /* Header for class com_ldq_d_string_D_string */ #ifndef _Included_com_ldq_d_string_D_string #define _Included_com_ldq_d_string_D_string #ifdef __cplusplus extern "C" { #endif /* * Class: com_ldq_d_string_D_string * Method: getCase * Signature: (Ljava/lang/String;)Ljava/lang/String; */ JNIEXPORT jstring JNICALL Java_com_ldq_d_1string_D_1string_getCase (JNIEnv *, jobject, jstring); #ifdef __cplusplus } #endif #endif

 

• 编写源代码文件 Case.cpp

#include
#include "com_ldq_d_string_D_string.h"

JNIEXPORT jstring JNICALL Java_com_ldq_d_1string_D_1string_getCase (JNIEnv *env, jobject obj, jstring string)
{
    const char *s=env->GetStringUTFChars(string,0);
    char s1[16],s2[16];
    strcpy(s1,s);
    strcpy(s2,s);
    strupr(s1);
    strlwr(s2);
    strcat(s1,"_");
    strcat(s1,s2);
    env->ReleaseStringUTFChars(string,s);
    return env->NewStringUTF(s1);
}

#include #include "com_ldq_d_string_D_string.h" JNIEXPORT jstring JNICALL Java_com_ldq_d_1string_D_1string_getCase (JNIEnv *env, jobject obj, jstring string) { const char *s=env->GetStringUTFChars(string,0); char s1[16],s2[16]; strcpy(s1,s); strcpy(s2,s); strupr(s1); strlwr(s2); strcat(s1,"_"); strcat(s1,s2); env->ReleaseStringUTFChars(string,s); return env->NewStringUTF(s1); }

 

• cl /LD Case.cpp 编译生成 Case.dll 文件
• 拷贝 Case.dll 文件到工程目录，运行 Java 程序 

运行结果

before change: heLLo
after change: HELLO_hello