自定义 TypeHandler

自定义TypeHandler分为三个步骤：

1、编写自定义TypeHandler，并继承自抽象类BaseTypeHandler<T>，实现抽象方法

2、在mybatis-config.xml配置文件的Configuration中注册自定义的TypeHandler

3、在Mapper.xml中使用自定义的TypeHandler

示例：

MyBooleanTypeHandler.java

public class MyBooleanTypeHandler extends BaseTypeHandler<Boolean> {
    public void setNonNullParameter(PreparedStatement preparedStatement, int i, Boolean aBoolean, JdbcType jdbcType) throws SQLException {
        preparedStatement.setString(i, String.valueOf(aBoolean));
    }

    public Boolean getNullableResult(ResultSet resultSet, String s) throws SQLException {
        String r = resultSet.getString(s);
        if (r != null && !r.equals("")){
            return Boolean.parseBoolean(r);
        }
        return null;
    }

    public Boolean getNullableResult(ResultSet resultSet, int i) throws SQLException {
        String r = resultSet.getString(i);
        if (r != null && !r.equals("")){
            return Boolean.parseBoolean(r);
        }
        return null;
    }

    public Boolean getNullableResult(CallableStatement callableStatement, int i) throws SQLException {
        String r = callableStatement.getString(i);
        if (r != null && !r.equals("")){
            return Boolean.parseBoolean(r);
        }
        return null;
    }
}

Mybatis-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <properties resource="jdbc.properties"/>

    <typeAliases>
        <package name="com.learn.pojo"/>
    </typeAliases>

    <typeHandlers>
        <typeHandler handler="com.learn.type.MyBooleanTypeHandler"/>
    </typeHandlers>

    <environments default="dev">
        <environment id="dev">
            <transactionManager type="JDBC">
            </transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="Mapper/UserMapper.xml"/>
    </mappers>

</configuration>

UserMapper.xml

<insert id="addUser" parameterType="user">
    insert into user (userName, password, isLogin)
    values (#{userName}, #{password} #{isLogin, typeHandler=com.learn.type.MyBooleanTypeHandler});
</insert>

注册自定义TypeHandler有两种方法：

1、在mybatis-config.xml中配置

<typeHandlers>
    <typeHandler handler="com.learn.type.MyBooleanTypeHandler" javaType="boolean" jdbcType="VARCHAR"/>
</typeHandlers>

2、使用注解配置

@MappedJdbcTypes(JdbcType.VARCHAR)
@MappedTypes(java.lang.Boolean.class)
public class MyBooleanTypeHandler extends BaseTypeHandler<Boolean> {...}

使用自定义注解一般有两种方式：

1、

<insert id="addUser" parameterType="user">
    insert into user (userName, password, isLogin)
    values (#{userName}, #{password}, #{isLogin, typeHandler=com.learn.type.MyBooleanTypeHandler});
</insert>

2、

<insert id="addUser" parameterType="user">
    insert into user (userName, password, isLogin)
    values (#{userName}, #{password}, #{isLogin, javaType=java.lang.Boolean, jdbcType=VARCHAR});
</insert>