解决Jackson的jar包导入，程序无法正常运行问题

今天看到很多人使用Jackson进行Java和json、xml之间相互转换，所以自己尝试使用jackson
下载地址：https://oss.sonatype.org/content/repositories/snapshots/com/fasterxml/jackson/core/
但是在使用的时候出现了这样的错误：

Duplicate files copied in APK META-INF/LICENSE.txt File

看log是因为在三个jar包中多了META-INF/LICENSE这样一个文件，在build.gradle文件下Android{}中添加这样一段代码：

packagingOptions {
    exclude 'META-INF/LICENSE'
    exclude 'META-INF/NOTICE'
  }

问题解决了。

原来的代码：

apply plugin: 'com.android.application'

android {
  compileSdkVersion 25
  buildToolsVersion "25.0.0"

  defaultConfig {
    applicationId "com.xd.jacksondemo"
    minSdkVersion 15
    targetSdkVersion 25
    versionCode 1
    versionName "1.0"

    testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
  }
  buildTypes {
    release {
      minifyEnabled false
      proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
  }
}

dependencies {
  compile fileTree(include: ['*.jar'], dir: 'libs')
  androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
    exclude group: 'com.android.support', module: 'support-annotations'
  })
  compile 'com.android.support:appcompat-v7:25.0.0'
  testCompile 'junit:junit:4.12'
  compile files('libs/jackson-core-2.2.3.jar')
}

修改后的代码：

apply plugin: 'com.android.application'

android {
  compileSdkVersion 25
  buildToolsVersion "25.0.0"
  packagingOptions {
    exclude 'META-INF/LICENSE'
    exclude 'META-INF/NOTICE'
  }

  defaultConfig {
    applicationId "com.xd.jacksondemo"
    minSdkVersion 15
    targetSdkVersion 25
    versionCode 1
    versionName "1.0"

    testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
  }
  buildTypes {
    release {
      minifyEnabled false
      proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
  }
}

dependencies {
  compile fileTree(include: ['*.jar'], dir: 'libs')
  androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
    exclude group: 'com.android.support', module: 'support-annotations'
  })
  compile 'com.android.support:appcompat-v7:25.0.0'
  testCompile 'junit:junit:4.12'
  compile files('libs/jackson-core-2.2.3.jar')
}