The function of each jar package in the Android system directory

This article is reprinted from http://blog.csdn.net/qq435757399/article/details/21402795, slightly modified according to our company's products:

1. am.jar: The java library required to execute the am command under the terminal. Source directory: framework/base/cmds/am
2. android.policy.jar: the jar package needed for the lock screen interface, which references android.test.runner.jar, source code directory: framework/base/policy
3. android.test.runner.jar: The jar package required for testing applications, which references core.jar, core-junit.ajr and framework.jar, source code directory: framework/base/test-runner
4. bmgr.jar: The java library required to back up and restore all packages of the Android Device under the adb shell command. Official documentation: http://developer.android.com/guide/developing/tools/bmgr.html . However, this android service is Disabled by default, and the application to be backed up must implement BackupAgent, and add the android:backupAgent attribute to the application tag of AndroidManifest.xml. Source directory: framework/base/cmds/bmgr
5. bouncycastle.jar: Java tripartite key library, online information says it is used for apk signature, https link and so on, official website: http://www.bouncycastle.org/java.html
6. com.android.future.usb.accessory.jar: The upper-layer java library used to manage USB, which will be called by the hardware layer when the system is compiled. Source directory: frameworks/base/libs/usb
7. com.android.location.provider.jar：
8. com.android.nfc_extras.jar: NFC external library. android/nfc/NfcAdapter.java will call NfcAdapterExtras.java in the package. Source directory: frameworks/base/nfc-extras
9. core-junit.jar: junit core library, which is called when running *Test.apk.
10. core-tests*.jar: A series of test jar packages under the framework, which can be deleted when no tests are performed.
11. core.jar: The core library, this is loaded first when the desktop is started. Source directory: 
12. ext.jar: Android external three-party extension package, the source code is mainly external/nist-sip (sip three-party library under java), external/apache-http (apache java three-party library), external/tagsoup (HTML parsing in line with SAX standard device). In fact, this jar package can add external extended jar packages, just add the src directory to ext-dirs in framework/base/Android.mk.
13. framework-res.apk: android system resource library.
14. framework.jar: the core code in the android sdk.
15. ime.jar: The jar package required by the ime command, used to view the current phone input method list and set the input method. Source directory: framework/base/cmds/ime
16. input.jar: The jar package required by the input command, used to simulate key input. Source directory: framework/baes/cmds/input
17. javax.obex.jar: java Bluetooth API for object exchange protocol. Source directory: framework/base/obex
18. monkey.jar: The jar package required to execute the monkey command. Source directory: framework/base/cmds/monkey
19. pm.jar: the jar package required to execute the pm command, see adb shell pm for details of pm, source code directory: framework/base/cmds/pm
20. services.jar: The compiled jar package of the phone framework layer server, cooperate with libandroid_servers.so to add each service to ServiceManager through SystemServer in a closed-loop management manner when the phone starts. Source directory: framework/base/service
21. sqlite-jdbc.jar： sqlite的Java DataBase Connextivity jar包。
22. svc.jar: The jar package required by the svc command, which can be used to manage wifi, power and data. Source directory: framework/base/cmds/svc