android JDBC mysql java连接器app：preDexDebug

问题描述

我试图学习如何使用JDBC将应用程序连接到mysql数据库。

我正在使用Android Studio。

我下载了来自de mysql网站的mysql-connector-java-5.1.37。

只需将mysql-connector-java-5.1.37-bin.jar放在Hello World应用程序的libs文件夹中并编译即可：

Im trying to learn how to use the JDBC to connect a application to a mysql database.
Im using the Android Studio.
I downloaded "mysql-connector-java-5.1.37" from de mysql website.
Just for put the "mysql-connector-java-5.1.37-bin.jar" in libs folder of a Hello World application and compile i recive :

build.gradle：

the build.gradle:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 23
    buildToolsVersion "22.0.1"

    defaultConfig {
        applicationId "br.com.myaplication.helloworld"
        minSdkVersion 15
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.1.0'
}

请帮帮我:) thnx

please, help me :) thnx

推荐答案

因为分布式mysql-connector- java-5.1.37-bin.jar是为Java1.8编译的，当前的Android dex编译器无法识别它。

Because Distributed mysql-connector-java-5.1.37-bin.jar is compiled for Java1.8, current Android dex compiler cannot recognize it.

$ javap -v com/mysql/jdbc/JDBC42Helper.class| grep "major version"
  major version: 52

另一方面，mysql-connector -java-5.1。 36 .jar是为Java1.6编译的。

On the oher hand, mysql-connector-java-5.1.36.jar is compiled for Java1.6.

$ javap -v com/mysql/jdbc/JDBC4Connection.class |grep "major version"
  major version: 50

，因此需要Java1.8。

5.1.37 supports JDBC4.2, so requires Java1.8.

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