Dealing with Enterprise Database Challenges

Transcription

1 Dealing with Enterprise Database Challenges Featuring the Apache ibatis Data Mapping Framework Scope ibatis Data Mapping Framework Introduction, SQL Mapping defined, examples. SQL Is it still relevant? ibatis is a hybrid solution Features, qualities, competition, other solutions. The Challenges Ownership, access, complexity, normalization, skinny design. An Introduction to Apache ibatis SQL Mapping defined

2 Concept SQL Mapping SQL as a Black Box OUTPUT OUTPUT SELECT FIRST_NAME, LAST_NAME FROM EMPLOYEE WHERE EMPLOYEE_NUMBER = 1234 INPUT SQL Mapping Maps objects to SQL statements NOT Classes to Tables Fully functional SQL via named statements NOT generated SQL (although that s possible) For example

3 CLASSES Order id : int total : BigDecimal pst : BigDecimal gst : BigDeciml lineitems : Collection date : Date LineItem id : int product : Product order : Order cost : BigDecimal retail : BigDecimal Product id : int name : String description : String cost : BigDecimal retail : BigDeciml TABLES Mapping Layer Order LineItem Product The Product Table PRODUCT PRODUCT_ID NAME DESCRIPTION COST RETAIL INTEGER VARCHAR TEXT MONEY MONEY PK, NN NN NN NN NN The Person Class public class Product { private int id; private String name; private String description; private BigDecimal cost; private BigDecimal retail; // getters/setters implied }

4 The SQL <select id= getproduct" parameterclass= int resultclass="examples.domain.product"> SELECT PRODUCT_ID as id, NAME, DESCRIPTION, COST, RETAIL, FROM PRODUCT WHERE PRODUCT_ID = #id# </select> Simple Configuration String resource = SqlMapConfig.xml ; Reader reader = Resources.getResourceAsReader (resource); SqlMapClient sqlmap = SqlMapClientBuilder.buildSqlMapClient(reader); Executing the Query Product product = (Product) sqlmap.queryforobject ( getproduct, 5);

5 Audience: OMG! Did you just hand code SQL? Clinton: Yes. SQL Is it still relevant? SQL Structured Query Language Introduced in 1973 by IBM Based on relational model of 1970 Based on sound mathematical principles Significant industry investment Has withstood the test of time Nothing else has even come close

6 SQL is much more than a simple data update and retrieval mechanism. SQL's query processing can perform many tasks. By hiding SQL, application developers are excluding a powerful tool. Writing SQL is NOT a Sin! Is SQL what we want to avoid? SELECT * FROM EMPLOYEE WHERE EMPLOYEE_NUMBER = 99

7 Or is it JDBC? public Employee getemployee (int id) throws SQLException { Employee employee = null; String sql = "SELECT * FROM EMPLOYEE " + "WHERE EMPLOYEE_NUMBER =?"; Connection conn = null; PreparedStatement ps = null; ResultSet rs = null; try { conn = datasource.getconnection (); ps = conn.preparestatement(sql); ps.setint(1, id); rs = ps.executequery(); employee = null; while (rs.next()) { employee = new Employee(); employee.setid (rs.getint("emp_id")); employee.setemployeenumber (rs.getint("emp_number")); employee.setfirstname (rs.getstring("emp_first_name")); employee.setlastname (rs.getstring("emp_last_name")); employee.settitle (rs.getstring("emp_title")); } } finally { try { if (rs!= null) rs.close(); } finally { try { if (ps!= null) ps.close(); } finally { if (conn!= null) conn.close(); } } } return employee; } ibatis is a hybrid solution Qualities, features and competition. Apache ibatis Is tolerant of complex/bad database designs Isolates the data model Separates concerns Divides labor Saves time Reduces code Can improve overall performance

8 Advanced ibatis Features Supports all types Objects, Primitives, Arrays, Collections Caching (use case vs. holistic) Lazy Loading or Join Mapping (1:1, 1:M, M:N) Bytecode enhancement XML parameters and results Transaction Management (Local/Global) But yes SQL Coding is Required Many people consider this an advantage Many others eventually realize it s required Few people consider it a problem SQL can be done fast and done well Use good tools (there are plenty) Generation is an option (but not a best practice) The SQL may already exist (consider app rewrites or ports) Other SQL Mapper-Like Tools JDBC PreparedStatement Embedded SQL as a language feature Pro*C, Forte TOOL, SQLJ Spring framework Voruta SQLC (ibatis inspired?) O/R Broker (ibatis inspired) Mr. Persister (ibatis inspired) Aximol SQL Library (ibatis inspired)

9 Other Solutions Stored procedures Inline SQL Dynamic SQL Object Relational Mapping ibatis IS A HYBRID! A Hybrid? Full support for stored procedures SQL is written just like inline SQL Inline SQL for XML Advanced dynamic SQL definition features A big problem even for the best ORM tools Shares many features with ORM Caching, lazy loading, join mapping, bytecode enhancement etc. The Challenges Welcome, to the real world. go for the red pill

10 Challenges of Politics boo! Database ownership and control Change management Cost allocation who pays for changes? No developer access to design Proprietary/3 rd Party legal issues Agile methods vs. legacy methods ibatis isolates the data model, the SQL, the work and the responsibility. In doing so, it isolates much of the politics surrounding the enterprise database as well. Challenges of Imperfection doh! Denormalized models Super-normalized models Modeled Value Entities Thin data models (rows vs. columns) Implicit relationships Overcomplicated relationships

11 ibatis works even when the data model does not map to the object model. Challenges of Legacy OMG! Too many tables to map Encoded Fields No primary keys Hierarchical ERP systems Yo DB so old, its primary keys are in Roman numerals! ibatis allows you to build modern applications on top of legacy databases by allowing you more freedom to define and tune your mappings that deal with unique databases.

12 Challenges of Technology Yay! Distributed transactions Distributed caching Vendor specific database features Break sponsored by Audience Response Questions?

13 More simple examples To inspire questions or support answers. <select id="getproduct" parameterclass= int resultclass= com.domain.product"> select PRODUCT_ID as id, NAME as name, DESCN as description, CATEGORY as category from PRODUCT where PRODUCTID = #id# </select> <resultmap id="productresult class="com.domain.product"> <result property="id" column="productid"/> <result property="name" column="name"/> <result property="description" column="descn"/> <result property="categoryid" column="category"/> </resultmap> <select id="getproduct parameterclass= int resultmap="productresult"> select * from PRODUCT where PRODUCTID = #id# </select>

14 <parametermap id="productparameter class= int"> <parameter property= id"/> </parametermap> <select id="getproduct parametermap= productparameter resultclass= com.domain.product > select PRODUCT_ID as id, NAME as name, DESCN as description, CATEGORY as category from PRODUCT where PRODUCTID =? </select> <statement id= insertproduct parameterclass= com.domain.product > insert into PRODUCT values (#id#,#name#,#description#,#category#) </statement> <statement id= updateproduct parameterclass= com.domain.product > update PRODUCT set NAME = #name#,desc = #description#,category=#category# where PRODUCT_ID = #id# </statement> <statement id= deleteproduct parameterclass= com.domain.product > delete PRODUCT where PRODUCT_ID = #id# </statement> Simple Query Product product =(Product) sqlmap.queryforobject ( getproduct, 23);

15 Insert, Update, Delete Product product = new Product(); product.setid(324); product.setname( Shih Tzu ); Product.setDescription( Some longer description. ); product.setcategory( DOG ); sqlmap.insert( insertproduct, product); product.setcategory( CAT ); sqlmap.update( updateproduct, product); product.delete( deleteproduct, product); Transaction Handling try { sqlmap.starttransaction(); sqlmap.insert( insertproduct, product); sqlmap.update( updateproduct, product); product.delete( deleteproduct, product); sqlmap.committransaction(); } finally { sqlmap.endtransaction(); } What does an application using SQL Maps look like? See JPetStore 4