iBATS文档

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### iBATS 文档知识点详解 #### 一、概述 **iBATS 数据映射框架** 是一个旨在大幅度减少访问关系数据库所需的 Java 代码量的工具。它通过使用简单的 XML 描述符将 JavaBean 映射到 SQL 语句上，从而实现了其核心功能。iBATS 的优势在于其简单性，相较于其他框架或对象关系映射 (ORM) 工具，它更加轻量级且易于上手。 #### 二、安装与升级 ##### 安装 iBATS 的安装过程相对简单，主要涉及将 iBATS 相关的库添加到项目中。通常情况下，这可以通过 Maven 或者 Gradle 的依赖管理来完成。此外，还需要创建配置文件来定义数据源、事务管理器等组件。 ##### 升级 对于从 1.x 版本升级到 2.0 版本的过程，开发者需要注意以下几点： - **配置文件变化**：新版本可能引入了新的配置选项或者移除了旧的配置项。 - **API 变更**：2.0 版本可能包含 API 的重大变更，因此需要检查文档以确保使用的 API 是否已经改变。 - **性能改进**：新版本可能包含性能优化方面的改进，升级后可以带来更好的执行效率。 #### 三、SQL Map XML 配置文件 **SQL Map XML 配置文件** 是 iBATS 中的核心配置文件之一，用于指定各种配置信息，包括属性设置、别名定义、事务管理器和数据源等。 ##### 《属性》元素 此元素用于定义全局的属性，这些属性可以在整个配置文件中被引用。 ##### 《设置》元素 《设置》元素用于指定一系列的配置参数，例如缓存启用状态、数据库类型等。 ##### 《resultObjectFactory》元素 此元素用于指定结果对象工厂的实现类，该工厂负责根据查询结果创建对应的 JavaBean 对象。 ##### 《typeAlias》元素 用于定义类型别名，简化了在配置文件中对复杂类型的引用。 ##### 《transactionManager》元素 指定事务管理器的配置，包括事务处理的方式以及相关的类库。 ##### 《dataSource》元素 定义数据源的相关配置，包括数据库连接的 URL、用户名、密码等信息。 ##### 《sqlMap》元素 该元素用于指定具体的 SQL 映射文件的位置和名称。 #### 四、SQL 映射文件 **SQL 映射文件** 包含具体的 SQL 查询语句和对应的 Java 类型映射规则。 ##### 映射语句 映射语句定义了 SQL 语句与 Java 方法之间的映射关系。 ##### 声明类型 定义了 SQL 语句的类型，包括 INSERT、UPDATE、DELETE 和 SELECT 等。 ##### SQL 定义具体的 SQL 语句，包括 SELECT、INSERT 等。 ##### SQL 片段重用 支持 SQL 片段的重用，提高了代码复用性和维护性。 ##### 自动生成键 支持插入操作时自动获取主键值的功能。 ##### 存储过程 支持调用数据库中的存储过程，并定义相应的输入输出参数。 ##### 参数映射与内联参数 提供了参数映射和内联参数的定义方式，使得参数传递更加灵活。 ##### 结果映射 结果映射用于定义如何将查询结果映射到 JavaBean 对象上，包括简单的数据类型映射和复杂的对象映射。 #### 五、动态 SQL iBATS 支持动态 SQL，即在运行时根据条件动态构建 SQL 语句的能力。 ##### 动态元素 定义了用于动态构建 SQL 的元素，如 `if`、`choose`、`when`、`otherwise` 等。 ##### 二进制条件元素 支持基于条件的 SQL 片段的插入或排除，如 `<if>` 标签。 ##### 一元条件元素 用于控制 SQL 片段的插入，如 `<trim>`、`<where>`、`<set>` 等。 #### 六、API 使用 iBATS 提供了一系列 API 来支持开发者的编程工作，包括配置管理、事务处理等方面。 ##### 配置 通过 API 可以加载配置文件并进行配置的初始化。 ##### 事务 提供了事务开始、提交和回滚的方法，简化了事务处理的复杂度。 ##### 多线程编程 支持多线程环境下的数据库操作，确保线程安全。 #### 七、日志记录 iBATS 支持记录 SQL 执行的日志信息，方便调试和监控。 #### 八、国际化资源 支持国际化资源的加载和使用，便于不同语言环境下的应用开发。 #### 九、总结 iBATS 数据映射框架为开发者提供了一种简洁高效的方式来处理数据库操作。通过其丰富的配置选项和灵活的动态 SQL 支持，可以大大减少编写冗余代码的工作量。无论是简单的 CRUD 操作还是复杂的查询逻辑，iBATS 都能够提供一套完善的解决方案。对于想要提高开发效率同时保持代码质量的开发者来说，iBATS 是一个非常值得考虑的选择。
Data Mapper
(a.k.a SQL Maps)
Version 2.0
Developer Guide
November 30, 2006
Developer Guide iBATIS Data Mapper 2.0
Table of Contents
......................................................................................................................................................................... 3
Introduction.......................................................................................................................................................4
Data Mapper..................................................................................................................................................... 4
Installation........................................................................................................................................................ 5
Upgrading from 1.x.....................................................................................................................................5
The SQL Map XML Configuration File ..........................................................................................................8
The <properties> Element...........................................................................................................................9
The <settings> Element...............................................................................................................................9
The <resultObjectFactory> Element.........................................................................................................12
The <typeAlias> Element......................................................................................................................... 13
The <transactionManager> Element.........................................................................................................13
The <dataSource> Element.......................................................................................................................14
The <sqlMap> Element.............................................................................................................................17
The SQL Map XML File ............................................................................................................................... 18
Mapped Statements.........................................................................................................................................19
Statement Types........................................................................................................................................19
The SQL....................................................................................................................................................21
Reusing SQL Fragments........................................................................................................................... 21
Auto-Generated Keys................................................................................................................................22
Stored Procedures..................................................................................................................................... 23
Parameter Maps and Inline Parameters.......................................................................................................... 28
Inline Parameter Maps.............................................................................................................................. 30
Primitive Type Parameters........................................................................................................................32
Map Type Parameters............................................................................................................................... 32
Substitution Strings.........................................................................................................................................33
Result Maps.................................................................................................................................................... 33
Implicit Result Maps.................................................................................................................................36
Primitive Results....................................................................................................................................... 36
Complex Properties ..................................................................................................................................37
Avoiding N+1 Selects (1:1)...................................................................................................................... 38
Complex Collection Properties ................................................................................................................ 39
Avoiding N+1 Selects (1:M and M:N)......................................................................................................40
Composite Keys or Multiple Complex Parameters Properties .................................................................41
Supported Types for Parameter Maps and Result Maps.................................................................................43
Creating custom Type Handlers................................................................................................................44
Caching Mapped Statement Results............................................................................................................... 45
Read-Only vs. Read/Write........................................................................................................................ 45
Serializable Read/Write Caches................................................................................................................45
Cache Types..............................................................................................................................................46
Dynamic Mapped Statements......................................................................................................................... 49
Dynamic Element......................................................................................................................................50
Binary Conditional Elements.................................................................................................................... 50
Unary Conditional Elements .................................................................................................................... 51
Other Elements..........................................................................................................................................52
Simple Dynamic SQL Elements..................................................................................................................... 54
Programming with Data Mapper: The API....................................................................................................55
Configuration............................................................................................................................................ 55
Transactions.............................................................................................................................................. 55
Multi Threaded Programming...................................................................................................................58
iBATIS Classloading................................................................................................................................ 58
Batches......................................................................................................................................................59
Executing Statements via the SqlMapClient API......................................................................................60
Logging SqlMap Activity............................................................................................................................... 65
The One Page JavaBeans Course................................................................................................................... 67
Resources (com.ibatis.common.resources.*) .................................................................................................69
http://ibatis.apache.org by Clinton Begin
2
Developer Guide iBATIS Data Mapper 2.0
Internationalization of Resources..............................................................................................................69
SimpleDataSource (com.ibatis.common.jdbc.*).............................................................................................71
http://ibatis.apache.org by Clinton Begin
3
Developer Guide iBATIS Data Mapper 2.0
Introduction
The iBATIS Data Mapper framework will help you to significantly reduce the amount of Java code that you
normally need to access a relational database. iBATIS simply maps JavaBeans to SQL statements using a
very simple XML descriptor. Simplicity is the key advantage of iBATIS over other frameworks and object
relational mapping tools. To use the iBATIS Data Mapper you need only be familiar with JavaBeans, XML
and SQL. There is very little else to learn. There is no complex scheme required to join tables or execute
complex queries. Using Data Mapper you have the full power of real SQL at your fingertips.
Data Mapper (com.ibatis.sqlmap.*)
Concept
The iBATIS Data Mapper API allows programmers to easily map JavaBeans objects to PreparedStatement
parameters and ResultSets. The philosophy behind Data Mapper is simple: provide a simple framework to
provide 80% of JDBC functionality using only 20% of the code.
How does it work?
Data Mapper provides a very simple framework for using XML descriptors to map JavaBeans, Map
implementations, primitive wrapper types (String, Integer…) and even XML documents to an SQL
statement. The following is a high level description of the lifecycle:
1. Provide an object as a parameter (either a JavaBean, Map or primitive wrapper). The
parameter object will be used to set input values in an update statement, or where clause values
in a query, ...
2. Execute the mapped statement. This step is where the magic happens. The Data Mapper
framework will create a PreparedStatement instance, set any parameters using the provided
parameter object, execute the statement and build a result object from the ResultSet.
3. In the case of an update, the number of rows effected is returned. In the case of a query, a
single object, or a collection of objects is returned. Like parameters, result objects can be a
JavaBean, a Map, a primitive type wrapper or XML.
The diagram below illustrates the flow as described.
http://ibatis.apache.org by Clinton Begin
4
JDBC
Parameter Object
(Input)
Map
(HashMap,
TreeMap…)
Result Object
(Output)
“Primitive”
(Integer,
String…)
Map
(HashMap,
TreeMap…)
JavaBean
SQL Map
Mapped
Statemen
Mapped
Statemen
Mapped
Statemen
Mapped
Statemen
Mapped
Statemen
Mapped
Statemen
Mapped
Statemen
Mapped
Statemen
Mapped
Statemen
XML
“Primitive”
(Integer,
String…)
SqlMapConfig.xml
SqlMap.
xml
SqlMap.
xml
JavaBean
XML
Developer Guide iBATIS Data Mapper 2.0
Installation
Installing the iBATIS Data Mapper framework is simply a matter of placing the appropriate JAR files on
the classpath. This can either be the classpath specified at JVM startup time (java -cp argument), or it could
be the /WEB-INF/lib directory of a web application. A full discussion of the Java classpath is beyond the
scope of this document. If you’re new to Java and/or the classpath, please refer to the following resources:
http://java.sun.com/j2se/1.4/docs/tooldocs/win32/classpath.html
http://java.sun.com/j2se/1.4.2/docs/api/java/lang/ClassLoader.html
http://java.sun.com/j2se/1.4.2/docs/
iBATIS is delivered in a single JAR file. The file name is in this form:
ibatis-version.build.jar
For example, ibatis-2.3.0.677.jar.
Generally, placing this single JAR file on your application's class path is enough.
JAR Files and Dependencies
When a framework has too many dependencies, it makes it difficult to integrate into an application and with
other frameworks. One of the key focus points of 2.0 was dependency management and reduction.
Therefore, if you're running JDK 1.4, then iBATIS has no other dependencies. The optional JAR file
libraries can be downloaded from the websites below. They are categorized by function. The following is a
summary of when you would need to use the optional packages.
Description When to Use Dependency
Legacy JDK
Support
If you're running less than JDK
1.4 and if your app server also
doesn't already supply these
JARs, then you will need these
optional packages.
JDBC 2.0 Extensions
http://java.sun.com/products/jdbc/download.html
JTA 1.0.1a
http://java.sun.com/products/jta/
Xerces 2.4.0
http://xml.apache.org/xerces2-j/
iBATIS Backward
Compatibility
If you’re using the old iBATIS
(1.x) DAO framework, or the
old Data Mapper (1.x) you can
continue to do so by simply
including the JAR files in this
directory.
iBATIS DAO 1.3.1
http://sourceforge.net/projects/ibatisdb/
Runtime
Bytecode
Enhancement
If you want to enable CGLIB
2.0 bytecode enhancement to
improve lazy loading and
reflection performance.
CGLIB 2.0
http://cglib.sf.net
DataSource
Implementation
If you want to use the Jakarta
DBCP connection pool.
DBCP 1.1
http://jakarta.apache.org/commons/dbcp/
Distributed
Caching
If you want to use OSCache
for centralized or distributed
caching support.
OSCache 2.0.1
http://www.opensymphony.com/oscache/
Logging Solution If you want to use Log4J
logging.
Log4J 1.2.8
http://logging.apache.org/log4j/docs/
Logging Solution If you want to use Jakarta
Commons Logging
Jakarta Commons Logging
http://jakarta.apache.org/commons/logging
Upgrading from 1.x
Should you Upgrade?
http://ibatis.apache.org by Clinton Begin
5

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