Java backend development: Using SQLAlchemy for API database ORM operations

With the development of the Internet, back-end technology in the architecture system has become an important field. With the continuous advancement of technology and changes in the underlying architecture, Java back-end technology is developing faster and faster, especially in ORM technology. API database ORM operation is an important area in back-end technology. This article will share the relevant experience of using SQLAlchemy for API database ORM operation.

1. Introduction to SQLAlchemy

SQLAlchemy is a SQL toolkit and object-relational mapper (ORM) for the Python programming language, which can provide flexible and efficient data access support in a variety of relational databases. Using SQLAlchemy, developers can write and easily execute SQL statements using the Python language. SQLAlchemy provides efficient underlying support for using SQL expressions and queries, managing connection pools, interacting with interactive debuggers, providing ORM functions.

2. API database ORM operation

1. Database connection

First, we need to initialize a database connection through the create_engine() method provided by SQLAlchemy. The create_engine() method requires a connection string used to connect to the database, for example:

from sqlalchemy import create_engine

engine = create_engine('mysql+pymysql://user:password@host:port/database')

where host represents the database host address to connect to, user represents the username used to connect to the database, and password represents the password used to connect to the database. , database represents the name of the connected database instance, and port represents the port used to connect to the database.

2. Define the data model

Next, define the data model. In SQLAlchemy, use the declarative_base() method to declare the data model and define tables and columns, for example:

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String

Base = declarative_base()

class Company(Base):
    __tablename__ = 'company'
    id = Column(Integer, primary_key=True)
    name = Column(String(50))
    address = Column(String(100))

In the above example, we define a data model named Company, where the __tablename__ attribute specifies The name of the database table mapped by the model; the id, name and address attributes correspond to the id, name and address columns in the table respectively.

3. Database CRUD operations

Next, we can use query operations to perform CRUD operations on the database. For example, we can perform an insert operation:

from sqlalchemy.orm import sessionmaker

Session = sessionmaker(bind=engine)

session = Session()

new_company = Company(name='Company 1', address='123 Main St.')

session.add(new_company)

session.commit()

In the above example, we first created a Session object, which is a session object linked to the database. Next, we can create a new Company object through the Session object and add it to the session object. After calling the session.commit() method, the new record will be inserted into the database table.

The code for querying data is as follows:

companies = session.query(Company).all()

In this example, we use the session.query() method to query all the data in the table corresponding to the Company data model and return a Python object. Each object corresponds to a row of data in the database.

Updating and deleting data operations are similar to the code for inserting data, so we won’t go into details here.

3. Summary

API database ORM operation is an important area in Java back-end development. Using SQLAlchemy allows us to obtain Python language while using Java for API database ORM operations. Flexibility and efficiency. Here, we first introduce the basic usage of SQLAlchemy. Next, we demonstrated through examples how to use SQLAlchemy to perform API database ORM operations, including database connection, data model definition and CRUD operations. This knowledge is very important for Java back-end developers.

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