Claim:

Java build a package, the package name of jdbc code database operated "cn.java.dao.impl"
Entity class, package name "cn.java.entity"
Tools, package name "cn.java.utils"

Configure Smart Templates

prompt:

Windows -> Preferences -> java - > editor -> Content Assist -> - "."> In the second line of the reciprocal after adding A _{the Z-and 0,} 9
Note Templates:

Windows -> Preferences -> java-> Code Style -> Code Templates -> import -> 导入 -> Windows -> Preferences -> java -> Editor -> Save Actions -> 选中：Format all lines
Format Templates:

Windows -> Preferences -> java-> Code Style -> Formatter -> import ->

First, preparation

1.1 reflection

### 1.1.1 obtain bytecode document:

Object name .getClass ();

Class c1 = user1.getClass();
Class name .class;

Class c2 = User.class;
Class.forName ( "full path byte code");

Class c3 = Class.forName(路径);

Over 1.2 thread

1.2.1 concept

process:

Program is being executed
Thread:

A thread is the process control unit, a process may have multiple threads.

Achieved in two ways 1.2.2 thread

Thread class inheritance:

The first step: writing an ordinary class, class inheritance thread

Step: Method override thread class is run, run method task code stored

The third step: start the thread: object name .start ();
Implement Runnable:

The first step: writing an ordinary class that implements the interface runnable

Step Two: Implement run method runnable interface, run task code storage method

The third step: start the thread: create a Thread object, the object name .start ();
```
Test1 test1 = new Test1();
Test1 test2 = new Test2();

Thread ts1 = new Thread(test1);
Thread ts2 = new Thread(test2);

ts1.state();
ts2.state();
```

1.2.3 The security thread: lock

Conditions occur:

Operating multiple threads share the same data
Solution:

A task to complete the locking block

        synchronized(类名.class){

            语句体

        }

Two, SQL language

type of data

Plastic
1. int
  1. int (m): m represents an expected value, regardless of the size and dimensions of the storage values
  2. zerofill zero padding, will fill in the left 0 (not a data type, can not be used alone)
```
 eg：

 id int(3) zerofill 当输入的id为“1”时，储存为“001”，当输入为“1000”时，zerofill不起作用
```
2. tinyint: 1 byte
3. smallint: 2 bytes
4. bigint: 8 bytes
5. mediumint: 3 bytes
Float
1. float
2. double
Character
1. char (m): a fixed-length string types, not just a character
2. varchar (m): a variable-length string type
3. text: string type large, 4G string
4. blob: Type Byte
date
1. date: date type, date
2. time: type of practice, minutes and seconds
3. year: Year in
4. timestamp: year, month, day, hour, time stamp
5. datetime: year, month, day, hour

Programming language

DDL: Data Definition Language
1. create
2. drop
3. alter
DML: Data Manipulation Language
1. insert
2. delete
3. update
DQL: Data Query Language
1. select
TCL: Transaction Control Language
1. commit: commit the transaction
2. rollback: transaction rollback
3. savepoint: Transaction Node
DCL: Data Control Language
1. grant: Authorization
2. revoke: take-over

2.0 Classification

DQL: Query preload
DML: Manipulation Language
DDL: Definition Language

2.1 library operations

Create a library:

create database 库名；

Create the specified encoding library:

create database library name character set encoding name;

Creating specify the encoding specified sorted set of libraries:

create database library name character set encoding name collate utf8_general_ci;
Delete a library:

drop database 库名；
Check the library to create information:

show create database 库名；
Change encoding library:

alert database library name character set encoding name;

2.2 Operating Table

Create a table:

create table 表名（

 字段 数据类型,

 字段 数据类型,

 primary key(已有字段)【注意：设置主键时，所有的主键为bigint，占20字节，写法：bigint(20)】

）；

Delete the table:

drop table name;
Modify the table:
1. Modify the table name:
  
  rename table the old table to the new table name;
2. Add field:
  
  alter table Table Field Name Data Type Name add;
3. Delete field:
  
  alter table drop table name field name;
4. Change the field name:
  
  alter table Old table name field name change column new data type field name;
5. Modify the field data type:
  
  alter table table modify the new data type field name;
Lookup table structure (including a table of data type fields and field):

desc table name;
Lookup table structure (built form of source code):

show create table 表名；
Copy the table:

create table table (select * from table);

Features: There is no primary key and increment

And add gradually increment:

2.2.1 Other keywords

not null
auto_increment
default defaults
comment comment content

2.3 data manipulation

adding data:
1. insert into table (field list) value (parameter list);
2. insert into table parameter set field 1 = 1, 2 ... Field field = 2;
change the data:

update table set a new value field name = 1, 2 = New field name value where the relational expression
delete data:

delete from table where conditional expression

truncate table table name [delete all the data, all the re-entry]
Query data:

select the field name [[as] alias] from table where conditional expression

2.4 cmd Mysql operation (first path configuration)

See how many libraries:

show databases;
Use the library (when selected):

use the table name
View current residence in which library:
1. select database();
2. \ S (more comprehensive)
See how many tables:

show tables；

2.5 MySQL query:

2.5.1 aggregate function

Function call:

select function name (parameter 1, parameter 2) [Others]
1. count: count the number of a parameter
  
  select count (userName) as the number of names from person appear;
  
  select count (*) as the total number of records from person;
2. max
3. me
4. avg
5. sum

2.5.2 Common Functions

concat (str1, str2 ... str3): string concatenation
NOW (): Gets the current system time
curDATE (): Get the current date
curDTIME (): Get the current time
rand (): random number fractional

2.5.3 Fuzzy query

select a field name, field name 2 ... from table where field names like conditions; (in% wildcards)

2.5.4 paging query

select * from table limit n(条数)
select * from table limit index，pageSize；

[Index = (pageNo-1) * afraid of a Size]

2.5.5 Sorting Query

select * from table [Condition] order by sort field desc / asc;

2.5.6 joint inquiry: union

select * from 表1 where id in （1，2，3）

union

select * from 表2 where id in (1,2,3,)

-> query results to weight: identical data only once

select * from 表1 where id in （1，2，3）

union all

select * from 表2 where id in (1,2,3,)

-> Show all results of the query: exactly the same data multiple times;

2.5.7 join queries (interview questions)

En:

select * from Table 1. Table 1 inner join alias alias 2 ON 2 where connection condition Filters
Outer join
1. Left connection:
  
  select * from Table 1 left where an alias filters join Table 2 ON 2 alias connection condition
2. Right Connections:
  
  select * from Table 1 1 right where alias filters join Table 2 ON 2 alias connection condition

2.6 custom function

grammar:

delimiter // [customize the terminator, or SQL default; as a statement terminator, the first statement within the function as a function of body]

create function function name (parameter type parameter name 1, parameter type name 2 ... Parameter) Returns the data type

begin
```
 declare result 返回类型 default 初始值；【声明变量和赋初始值】  

 SELECT money INTO ruslt FROM bankaccount WHERE id=ueserId;【变量赋值（实际例子）】  
```
end//

DELIMITER; [] will change back terminator
transfer:

select the function name (arguments);
delete:

drop function function name;

2.6.1 if

grammar:

then if the conditional expression
```
 SQL语句体  
```
elseif conditional expression then
```
 SQL语句体  
```
else
```
 SQL语句体  
```
end if

2.6.2 while

grammar:

while the conditional expression do
```
 SQL语句  
```
end while;

2.6.3 switch

grammar:

case mark

 when 实际 then   

     sql  

 else    

     sql

end case

2.6.4 increment

grammar:

set i = i+1；

2.7 storage process

grammar:

delimiter // [customize the terminator, or SQL default; as a statement terminator, the first statement within the function as a function of body]

create procedure stored procedure name (parameter type parameter name 1, parameter type name 2 Parameter ...) [not] Return Type

begin
```
 declare result 返回类型 default 初始值；【声明变量和赋初始值】  

 SELECT money INTO ruslt FROM bankaccount WHERE id=ueserId;【变量赋值（实际例子）】  
```
end//

DELIMITER; [] will change back terminator
transfer:

the name of the stored procedure call (argument);
delete:

drop procedure stored procedure name

2.8 Triggers

2.9 Constraints

default
not null
unique
primary key
foreign key
check: check constraint (MySQL does not support)
auto_increment
unsigned: Unsigned constraints. When the column specified non-negative value
zerofill: zero padding constraints

Three, JDBC

3.1 database connection

Java SQL server connection
Connect MySQL:
1. Through third-party connections:
  
  If the mysql database was closed by sqlyog is not connected, you need to manually open Mysql server: windows + r-> services.msc recall service options
2. MySQL comes
3. CMD

3.2 Junit unit testing

When a test method can not only run through:

Write "@Test", will get an error, then put up the mouse, select Junit on that instance methods. Right after the name of the method can be selected to run.

Specification writing

public void 方法名（）{代码块}    【没有参数，不能用static】

3.3 JDBC Procedure

Import driver package

Select the project - "Right -" New - "Folder -" fill in the Folder name at: lib - "copy to lib in the driver package -" The selected drive right package - "Build Path -" Add to Build Path - "in lib file appears above the "small bottle"
Load the driver

Class.forName(“com.mysql.jdbc.Driver”);
Connect to the database

DriverManager.getConnerction ( "jdbc: mysql: // localhost: 3306 / database name", user name, password) [package needs to lead, that the election Java.sql]

Because Java objects that everything in, so the procedure is also connected to the object, called "Connection Object"
Writing SQL statements, execute SQL statements, receiving feedback

String sql = "the original model as sql statement"

// Create a car

Statement st = conn.createStatement();

// The sql loading, driving

int result = st.exeuteUpdate(sql);

if(result >= 1){
```
 System.out.println("数据添加成功");  
```
}else{
```
 System.out.println("数据添加失败");
```
}

ResultSet rs = st.executeQuery(sql);

ResultSet There are two main methods: getObject ()

The name of the method parameter to be the same as the name of the database table field empty

If the database is Date type, using the received type String
Close the connection

st.close();

conn.close();

3.4 configuration file properties (can not be put under the table)

Storage location: new -> Source Folder -> named conf or resource -> new -> file -> name to ".properties" end

Features:
1. Only in the form of "key = value" of writing, a line of one pair
2. Only string type
Read:

Step 1: Create the properties object that represents the properties file
```
 1. 将对象与实际内容关联  

 2. 将关联后的对象变成流  
```
Step Two: read data object method

3.5 static block of code (interview point)

grammar
```
 static {



 }
```
Features: first executed before the constructor

Fourth, the database

4.1 Time conversion functions

grammar:

date_format(date,format);

This function type into a string of date

select date_foramt(publishTime,"%Y/%m%d %H:%i") from goods;

4.2 Transaction (transaction):

Definition: Multi marching as a whole, can not be divided
Steps:
1. Open transaction: start transaction
2. [Roll back the transaction: rollback] (only rollback operation before submitting valid)
3. Commit the transaction: commit
Features:
1. Atomicity (automic):
  
  Inseparable between each step
2. Consistency (consistent):
  
  The final total operation target unchanged
3. Isolation (isolation):
  
  No interference between transactions and transactions.
  
  There isolation 4z isolation levels: read uncommitted, read committed, repeatable read, serializable (4 levels higher and higher, the level of high-performance worse)
```
 查看MySQL数据库的隔离级别：select @@tx_isolation;

 修改MySQL数据库的隔离级别：set transaction isolation level 隔离级别【一次性】/set all transaction isolation level 隔离级别【永久性】;
```
  1. Dirty read:
    
    When the isolation level of the database to read uncommitted will lead to dirty read.
    
    Solution: The isolation of database software to read committed to
  2. Non-repeatable read:
    
    When the database isolation level is read committed would lead to non-repeatable read.
    
    Solution: The isolation of database software to as repeatable read
  3. Dummy read (phantom read):
    
    When the database isolation level is repeatable read will lead to non-repeatable read.
    
    Solution: The isolation of database software to as serializable
4. Endurance:
  
  Once the data is entered into the database, the database needs to ensure data security.

4.3 Database Backup and Restore

Backup:
1. Third-party software sqlyog
  
  General sql backup file, the file named "library name + _back"
2. MySQL command
  
  mysqldump -u username -p password database name> D: \ database name _back.sql [need to be performed under cmd, can not connect to the database when performing] [need to manually create a restore library]
reduction:
1. MYSQL command:
  
  source database backup files need to be performed in the script [cmd, you need to connect to the database when performing]

4.4 MySQL database coding

View:

show variables like "cha%" wildcards [%]
Change the database code:

set encoding variable name = name;

4.5 Check performance sql statement

grammar:

explain sql statement
Methods to improve performance:
1. To build a field general index
  1. grammar:
    
    create index index name on table name (field name)
  2. delete:
    
    drop index index name on table;
2. Partition table
3. Use Cached

Five, MD5 encryption

Features:
1. Take hex
2. No matter how long the old password, the encrypted into 32 (the number of the intermediate medium 16)

Sixth, stratified

UI layer (interface):

Package name: cn.java.ui

There are also packages stored entities: cn.java.entity

UI layer interfaces calling service layer
service Interface Layer:

Package name: cn.java.service
the service layer (the layer):

Package name: cn.java.service.impl

service layer interface to call dao layer, i.e., interfacial layer
dao Interface Layer:

Package name: cn.java.dao

Only put Interface
dao layer:

Package name: cn.java.dao.impl;

There is also a package store tools: cn.java.utils

dao layer mainly operate the database: CRUD, only as an example and the method can not be static

VII Framework BDUtils

Core classes:

QueryRunner

When you use objects to create QueryRunner
Query, the query execution method:
1. query(Connertion conn, String sql, ResultSetHandler rsh):
  
  The third parameter: indicates what type Returns: 1) Returns an object: new BeanHandler (object class name .class); 2) returns a collection of objects: new BeanListHandler (.class object class name);
2. query(Connertion conn, String sql, ResultSetHandler rsh，Object…params):
  
  The fourth parameter is the parameter sql, sql parameters with? instead.
Increase, execute the insert method:

return
(Increase) excision, perform the update method:

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JDBC study notes -MySql