Shulou(Shulou.com)06/03 Report--

What this article shares with you is about how to add, delete, modify and check MyBatis. The editor thinks it is very practical, so I share it with you to learn. I hope you can get something after reading this article.

As a happy small code farmer, at every stage, we often repeat different versions, student management, user management, registration and login, from the console version of JavaSE, or the GUI version, to the JSP version of JavaWeb, to the version that purely uses HTML as the front-end display, and to use an updated technology, in which we have used txt to do the database, XML can also be used, to the commonly used MySQL. Addition, deletion, modification and search has always been an indispensable part of our content, even if you do not understand the principle, even if you do not have a deep understanding of this technology, taking out your add, delete, change and search, crackling is a random knock, at least it can still get you started (of course, the understanding of the technology is still very important). Today we will talk about the CURD of MyBatis technology.

Optimize the test method

In the test method, reading configuration files, producing SqlSession, releasing resources, etc., are repeated in each test method, so we can propose this part to prevent a large number of duplicate code.

@ Before public void init () throws Exception {/ / read configuration file inputStream = Resources.getResourceAsStream ("SqlMapConfig.xml"); / / create SqlSessionFactory factory SqlSessionFactory factory = new SqlSessionFactoryBuilder () .build (inputStream); / / use factory production SqlSession object sqlSession= factory.openSession (); / / use SqlSession to create proxy object userMapper = sqlSession.getMapper (UserMapper.class) for Mapper interface;} @ After public void destroy () throws Exception {sqlSession.close (); inputStream.close ();}

Adding @ Before and @ Aftrer annotations to these two methods ensures that the init () and destory () methods are executed before and after the method we are actually testing.

(1) add operation (1) write code

First, add the corresponding method to the UserMapper interface

Public interface UserMapper {/ * add users * @ param user * / void addUser (User user);}

Next, in the SQL mapping file, add the new mapping configuration, which is placed in the tag pair, as follows

Insert into user (username,telephone,birthday,gender,address) values (# {username}, # {telephone}, # {birthday}, # {gender}, # {address})

(2) description:

1. The id attribute is naturally the corresponding method name, but since we do not need to get the return information here, the parameter resultType is not returned here, and the parameter in the method is a JavaBean class, that is, the User entity class, so you need to add a parameterType attribute to the tag attribute, where you need to specify this entity class.

2. Write the inserted SQL statement in the text, because the corresponding get set method has been quickly generated in the entity class, so you can use # {} to represent the corresponding value.

3. Note that the id in the database is self-increasing, so there is no need to set id.

(3) Note:

Since adding a statement that is an update class, after executing the insert statement, you need to commit the transaction, that is, execute the corresponding commit method to submit the update operation. Without this sentence, even if there is no error, it cannot be stored normally, it will be rolled back, and the id will be occupied.

(4) Test code:

/ * * Test new users * @ throws Exception * / @ Test public void testUpdateUser () throws Exception {User user = new User (); user.setId (17); user.setUsername ("modify"); user.setTelephone ("18899999999"); user.setBirthday (new Date ()); user.setGender ("female"); user.setAddress ("Guangzhou"); / / execution method userMapper.updateUser (user);}

(5) implementation result:

Console:

(6) obtain the id value of the new user

First of all, for the MySQL self-increment primary key, before executing the insert statement, MySQL will automatically generate a self-increment primary key. After insert execution, the self-increment primary key that has just been inserted into the record can be obtained through SELECT LAST_INSERT_ID ().

In the SQL mapping configuration file, with the help of tags, there is a special attribute, the order attribute, which represents the execution time relative to the insert operation, before before-, after after-

Note: the label is inserted into the

SELECT LAST_INSERT_ID ()

Test it

@ Testpublic void testAddUser () throws Exception {User user = new User (); user.setUsername ("add"); user.setTelephone ("12266660000"); user.setBirthday (new Date ()); user.setGender ("male"); user.setAddress ("Zhuhai"); System.out.println ("before execution insert" + user); / / execution method userMapper.addUser (user); System.out.println ("after execution insert" + user);}

Execution effect

(2) modify operation (1) write code

Add modification method to UserMapper interface

Public interface UserMapper {/ * update user * @ param user * / void updateUser (User user);}

Add a statement to the SQL mapping file, and the contents are included in. The basic points to note are the same as the add operation.

Update user set username=# {username}, telephone=# {telephone}, birthday=# {birthday}, gender=# {gender}, address=# {address} where id=# {id}

(2) Test code

/ * Test new users * @ throws Exception * / @ Test public void testAddUser () throws Exception {User user = new User (); user.setUsername ("increase"); user.setTelephone ("12266668888"); user.setBirthday (new Date ()); user.setGender ("female"); user.setAddress ("Chengdu"); / / execution method userMapper.addUser (user);}

(3) execution effect

(3) Delete operation (1) write code

Add deletion method to the interface

Public interface UserMapper {/ * Delete user * @ param uid * / void deleteUser (Integer uid);}

In the SQL mapping file, the tag pair is used to write the content. It should be noted that since the parameter we passed in is a user id of type Integer, the value of the parameter type is parameterType.

Delete from user where id=# {id}

(2) Test code

/ * Test Delete user * @ throws Exception * / @ Testpublic void testDeleteUser () throws Exception {/ / execution method userMapper.deleteUser (17);}

(3) execution effect

(4) Fuzzy query

Since the query is all very simple, it will not be shown here, and the basic process is the same.

(1) write code

Write methods in UserMapper interface

Public interface UserMapper {/ * through the name fuzzy query * @ param username * @ return * / List findByName (String username);}

Add query statement in SQL mapping file

Select * from user where username like # {username}

(2) Test code

/ * Test Fuzzy query * @ throws Exception * / @ Testpublic void testFindByName () throws Exception {List users = userMapper.findByName ("% Zhang%"); for (User user: users) {System.out.println (user);}}

(3) pay attention

When using a fuzzy query, we need to concatenate two "%" strings on both sides of the query condition. There are two solutions, one is to complete the string during the test, as in my above code, and the other is to use ${}, which represents a "concatenation symbol" in the SQL configuration file, that is, you can write the SQL statement like this.

Select * from user where username like'% {value}'

The acceptable types are normal type (in this case {} can only write value internally), JavaBean,HashMap

However, when using% {} to concatenate strings, it will cause SQL injection, so it is not recommended to use

(4) execution effect

(5) Custom wrapper class as query condition

In the sample input mapping of Mapper, we have some understanding of basic data types and basic data wrapper classes, but let's talk about a relatively complex situation, that is, custom wrapper classes.

Let's start with a requirement: still a query about the user, but the query conditions are a little more complex, not only limited to the user's information, but also may include orders, shopping carts, or information related to the user's behavior. so how to achieve such a demand?

So we were wondering if we could add some information we need to the User class.

From the point of view of the code, the fields added in User may not necessarily correspond to the database, and the modification based on the original will affect the function of User as a database mapping object, so we can create a UserInstance class, and inherit the User class to add some fields that do not belong to the database for some business.

(1) define the wrapper class

Package cn.ideal.domain;public class QueryUserVo {private UserInstance userInstance; public UserInstance getUserInstance () {return userInstance;} public void setUserInstance (UserInstance userInstance) {this.userInstance = userInstance;} / / other query criteria, such as orders, shopping carts, etc.}

(2) configure Mapper file

We use the user's gender and fuzzy query of the name to write SQL here, of course, you can also write SQL through other information.

Select * from user where user.gender=# {userInstance.gender} and user.username like # {userInstance.username}

In QueryUserVo, it encapsulates all kinds of objects that query information. Why can the above code extract the corresponding attributes directly through userInstance.gender? this way is called OGNL expression. In the class, we usually write user.getUsername, but in writing, OGNL expression omits get.

(3) Test code

/ * wrapper object as query parameter * @ throws Exception * / @ Testpublic void testFindUserByVo () throws Exception {/ / create wrapper object, set query condition QueryUserVo queryUserVo = new QueryUserVo (); UserInstance userInstance = new UserInstance (); userInstance.setGender ("female"); userInstance.setUsername ("% Zhang%"); queryUserVo.setUserInstance (userInstance); / / call UserMapper method List userInstances = userMapper.findUserByVo (queryUserVo); for (UserInstance u: userInstances) {System.out.println (u);}}

(4) execution effect

The above is how to add, delete, modify and check MyBatis. The editor believes that there are some knowledge points that we may see or use in our daily work. I hope you can learn more from this article. For more details, please follow the industry information channel.

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