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Basic process of the project

1. Preparatory work

Dependency packages introduced in pom.xml

Org.thymeleaf thymeleaf 3.0.12.RELEASE javax.servlet javax.servlet-api 3.1.0 provided mysql mysql-connector-java 5.1.49 com.fasterxml.jackson.core jackson-databind 2.12.3 Junit junit 4.13.1

Jackson dependency is introduced for serialization and deserialization.

Function: to make data and objects can be converted to each other to ensure the integrity of data

Jackson is a class library used by Java to process data in JSON format with excellent performance. It is often used for JSON serialization (converting objects to JSON strings) and deserialization (converting JSON strings to specified data types).

Serialization and deserialization operations:

Public class WebUtil {/ / determines whether to log in, and obtains the session through the request object. If the session exists and the key / / saved when logging in is user, and the value is the user object, this data exists, it means you are logged in / / user is returned: if you are logged in, return the user saved in session. If you are not logged in, return null public static User checkLogin (HttpServletRequest req) {User user = null. / / if you cannot get session,false from the map data structure of session saved by tomcat, return null HttpSession session = req.getSession (false); if (sessionkeeper null) {user = (User) session.getAttribute ("user");} return user;} / / this object can use singleton private static ObjectMapper M = new ObjectMapper () / / deserialization: convert json strings contained in an input stream to a java object / / use generics: if a type is passed to me, an object of that type public static T read (InputStream is,Class clazz) {try {return M.readValue (is,clazz);} catch (IOException e) {throw new RuntimeException ("json deserialization error", e) }} / / Serialization: converts an arbitrary type of java object into a json string public static String write (Object o) {try {return M.writeValueAsString (o);} catch (JsonProcessingException e) {throw new RuntimeException ("json serialization error", e);}} 2. Database design

1. Create the required table:

User (user table)

Acticle (article table)

two。 Design the corresponding database entity class:

3. Database connection tools:

/ / Database tool class: provides unified code public class DBUtil {/ / static variable for obtaining database connection and releasing resources, initializes when the class is loaded, executes private static MysqlDataSource ds; / / a program only once, connects to a database, only needs a connection pool, and stores multiple database connection objects / / 1. Get connection pool, internal use, do not open private static DataSource getDataSource () {/ / ds class load, initialize to null, when the method is used, every time you judge that if (ds==null) {/ / is empty, create and initialize the property ds=new MysqlDataSource (); ds.setURL ("jdbc:mysql://127.0.0.1:3306/blog") Ds.setUser ("root"); ds.setPassword ("010124"); ds.setUseSSL (false); / / unsecure connection, if not set, will not be affected, except that there is a warning ds.setCharacterEncoding ("UTF-8");} return ds;} / / 2. Get database connection object: open to external jdbc code to use public static Connection getConnection () {try {return getDataSource (). GetConnection ();} catch (SQLException e) {throw new RuntimeException ("error getting database connection, possibly url, account password is wrong", e);} / / 3. Release resources / / query operation requires the release of three resources, update operation (insert, modify, delete) only need to release the first two resources public static void close (Connection c, Statement s, ResultSet r) {try {if (ringing null) r.close (); if (slack null) s.close (); if (cased null) c.close () } catch (SQLException e) {throw new RuntimeException ("error releasing database resources", e);}} / / release resource function public static void close (Connection c, Statement s) {close (c);} public static void main (String [] args) {System.out.println (getConnection ());}}

4. CRUD actions for user table and article table (Dao class):

3. Prepare the front page

1. Deploy the previously written front-end static page to the webapp directory

two。 Encapsulate ajax:

In the front-end interaction, we need to use ajax for data interaction.

Copy the previously encapsulated ajax function and put it in a separate js file for later use.

Function ajax (args) {/ / var ajax = function () {} let xhr = new XMLHttpRequest (); / / set the callback function xhr.onreadystatechange = function () {/ / 4: after the client receives the response, the callback if (xhr.readyState = = 4) {/ / callback function may need to use the content of the response as the incoming parameter args.callback (xhr.status, xhr.responseText) }} xhr.open (args.method, args.url); / / if the contentType attribute has content in args, set the Content-Type request header if (args.contentType) {/ / js. If judges that, in addition to judging Boolean values, strings, objects, etc., if there is a value, it is true xhr.setRequestHeader ("Content-Type", args.contentType). } / / if the body request body is set in args, call send (body) if (args.body) {xhr.send (args.body);} else {/ / if not set, call send () xhr.send ();}}

3. Design a class to return to the front-end ajax callback

/ / Design a class to return to the front end ajax callback public class JsonResult {private boolean ok;// indicates whether the execution of an operation is successful private Object data;// operation is successful, and it is a query operation. You need to return some data to the front end / / also omitting getter, setter and toString} 4. Realize the required functions of the front-end matching Servlet

5. Project difficulty

To realize that the user is not allowed to access the contents of the home page and redirect to the login page if the user does not log in. Secondly, it is illegal to access an interface without logging in, and it is also necessary to redirect to the login page.

After the article is published, a new article should be inserted into the database. To view the full text, the data in markdown format should be converted to HTML.

After a successful login, you should also create a session and save the user information for later use.

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