C语言调用java的方法

发布时间：2020-07-01 11:01:25

来源：亿速云

阅读：86

作者：Leah

本篇文章为大家展示了C语言调用java的方法，代码简明扼要并且容易理解，绝对能使你眼前一亮，通过这篇文章的详细介绍希望你能有所收获。

步骤：

1. 创建虚拟机；

2. 获得class；

3. 实例化对象：获得构造方法(方法名为“”)，构造参数，调用方法。

4. 调用方法：又分为获得方法，构造方法，调用方法。

操作方法：

1. 编译：javac Hello.java

2. javap -p -s Hello.class：查看Signature

3. gcc -I/usr/lib/jvm/java-1.8.0-openjdk-amd64/include/ -I/usr/lib/jvm/java-1.8.0-openjdk-amd64/include/linux/ -o caller caller.c -L /usr/lib/jvm/java-8-openjdk-amd64/jre/lib/amd64/server -ljvm

4. 执行：LD_LIBRARY_PATH=/usr/lib/jvm/java-8-openjdk-amd64/jre/lib/amd64/server ./caller

举例：

(1)call_static_method#include

#include

JNIEnv* create_vm(JavaVM** jvm, JNIEnv** env)

{

JavaVMInitArgs args;

JavaVMOption options[1];

args.version = JNI_VERSION_1_6;

args.nOptions = 1;

options[0].optionString = "-Djava.class.path=./";

args.options = options;

args.ignoreUnrecognized = JNI_FALSE;

return JNI_CreateJavaVM(jvm, (void **)env, &args);

}

int main(int argc, char **argv)

{

JavaVM* jvm;

JNIEnv* env;

jclass cls;

int ret = 0;

jmethodID mid;

/* 1. create java virtual machine */

if(create_vm(&jvm, &env))

{

printf("can not create jvm\n");

return -1;

}

/* 2. get class */

cls = (*env)->FindClass(env, "Hello");

if(cls == NULL)

{

printf("can not find hello class\n");

ret = -1;

goto destory;

}

/* 3. create object */

/* 4. call method

* 4.1 get method

* 4.2 create parameter

* 4.3 call method

*/

mid = (*env)->GetStaticMethodID(env, cls, "main", "([Ljava/lang/String;)V");

if(mid == NULL)

{

ret = -1;

printf("can not get method\n");

goto destory;

}

(*env)->CallStaticVoidMethod(env, cls, mid, NULL);

destory:

(*jvm)->DestroyJavaVM(jvm);

return ret;

}

(2)call_non_static_method#include

#include

JNIEnv* create_vm(JavaVM** jvm, JNIEnv** env)

{

JavaVMInitArgs args;

JavaVMOption options[1];

args.version = JNI_VERSION_1_6;

args.nOptions = 1;

options[0].optionString = "-Djava.class.path=./";

args.options = options;

args.ignoreUnrecognized = JNI_FALSE;

return JNI_CreateJavaVM(jvm, (void **)env, &args);

}

int main(int argc, char **argv)

{

JavaVM* jvm;

JNIEnv* env;

jclass cls;

int ret = 0;

jmethodID mid;

jmethodID cid;

jobject jobj;

jstring jstr;

int r;

/* 1. create java virtual machine */

if(create_vm(&jvm, &env))

{

printf("can not create jvm\n");

return -1;

}

/* 2. get class */

cls = (*env)->FindClass(env, "Hello");

if(cls == NULL)

{

printf("can not find hello class\n");

ret = -1;

goto destory;

}

/* 3. create object

*

*/

cid = (*env)->GetMethodID(env, cls, "", "()V");

if(cid == NULL)

{

printf("can not get construct method\n");

ret = -1;

goto destory;

}

jobj = (*env)->NewObject(env, cls, cid);

if(jobj == NULL)

{

printf("can not create object\n");

ret = -1;

goto destory;

}

/* 4. call method

* 4.1 get method

* 4.2 create parameter

* 4.3 call method

*/

mid = (*env)->GetMethodID(env, cls, "sayhello_to", "(Ljava/lang/String;)I");

if(mid == NULL)

{

ret = -1;

printf("can not get method\n");

goto destory;

}

jstr = (*env)->NewStringUTF(env, "287787472@qq.com");

r = (*env)->CallIntMethod(env, jobj, mid, jstr);

printf("ret = %d\n", r);

destory:

(*jvm)->DestroyJavaVM(jvm);

return ret;

}

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